2010-11-20 Tatsuhiro Tsujikawa <t-tujikawa@users.sourceforge.net>

	Rewritten Logger interface. Logger now writes source file name and
	line number in log file.

197 files changed, 2057 insertions, 2698 deletions

diff --git a/ChangeLog b/ChangeLog
index f89d0a2d..11085934 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2010-11-20  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
+
+	Rewritten Logger interface. Logger now writes source file name and
+	line number in log file.
+
 2010-11-18  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
 
 	Made DHTBucketTreeNode non-copyable.
diff --git a/src/AbstractBtMessage.cc b/src/AbstractBtMessage.cc
index 07f88f5c..50d2d9c0 100644
--- a/src/AbstractBtMessage.cc
+++ b/src/AbstractBtMessage.cc
@@ -36,24 +36,21 @@
 #include "Peer.h"
 #include "PieceStorage.h"
 #include "BtMessageValidator.h"
-#include "LogFactory.h"
-#include "Logger.h"
 
 namespace aria2 {
 
-AbstractBtMessage::AbstractBtMessage(uint8_t id, const std::string& name):
-  BtMessage(id),
-  sendingInProgress_(false),
-  invalidate_(false),
-  uploading_(false),
-  cuid_(0),
-  name_(name),
-  dispatcher_(0),
-  messageFactory_(0),
-  requestFactory_(0),
-  peerConnection_(0),
-  metadataGetMode_(false),
-  logger_(LogFactory::getInstance())
+AbstractBtMessage::AbstractBtMessage(uint8_t id, const std::string& name)
+  : BtMessage(id),
+    sendingInProgress_(false),
+    invalidate_(false),
+    uploading_(false),
+    cuid_(0),
+    name_(name),
+    dispatcher_(0),
+    messageFactory_(0),
+    requestFactory_(0),
+    peerConnection_(0),
+    metadataGetMode_(false)
 {}
 
 AbstractBtMessage::~AbstractBtMessage() {}
diff --git a/src/AbstractBtMessage.h b/src/AbstractBtMessage.h
index 52cd24a3..475cace2 100644
--- a/src/AbstractBtMessage.h
+++ b/src/AbstractBtMessage.h
@@ -47,7 +47,6 @@ class BtMessageFactory;
 class BtRequestFactory;
 class PeerConnection;
 class BtMessageValidator;
-class Logger;
 
 class AbstractBtMessage : public BtMessage {
 private:
@@ -73,14 +72,7 @@ private:
   SharedHandle<BtMessageValidator> validator_;
 
   bool metadataGetMode_;
-
-  Logger* logger_;
 protected:
-  Logger* getLogger() const
-  {
-    return logger_;
-  }
-
   const SharedHandle<PieceStorage>& getPieceStorage() const
   {
     return pieceStorage_;
diff --git a/src/AbstractCommand.cc b/src/AbstractCommand.cc
index a35d7e25..1c11efc2 100644
--- a/src/AbstractCommand.cc
+++ b/src/AbstractCommand.cc
@@ -55,6 +55,7 @@
 #include "message.h"
 #include "prefs.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "ServerStat.h"
 #include "RequestGroupMan.h"
 #include "A2STR.h"
@@ -113,24 +114,20 @@ AbstractCommand::~AbstractCommand() {
 }
 
 bool AbstractCommand::execute() {
-  if(getLogger()->debug()) {
-    getLogger()->debug("CUID#%s - socket: read:%d, write:%d, hup:%d, err:%d",
-                       util::itos(getCuid()).c_str(),
-                       readEventEnabled(),
-                       writeEventEnabled(),
-                       hupEventEnabled(),
-                       errorEventEnabled());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - socket: read:%d, write:%d, hup:%d, err:%d",
+                   util::itos(getCuid()).c_str(),
+                   readEventEnabled(),
+                   writeEventEnabled(),
+                   hupEventEnabled(),
+                   errorEventEnabled()));
   try {
     if(requestGroup_->downloadFinished() || requestGroup_->isHaltRequested()) {
       return true;
     }
     if(req_ && req_->removalRequested()) {
-      if(getLogger()->debug()) {
-        getLogger()->debug
-          ("CUID#%s - Discard original URI=%s because it is requested.",
-           util::itos(getCuid()).c_str(), req_->getUri().c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - Discard original URI=%s because it is"
+                       " requested.",
+                       util::itos(getCuid()).c_str(), req_->getUri().c_str()));
       return prepareForRetry(0);
     }
     if(getPieceStorage()) {
@@ -140,11 +137,9 @@ bool AbstractCommand::execute() {
         // This command previously has assigned segments, but it is
         // canceled. So discard current request chain.  Plus, if no
         // segment is available when http pipelining is used.
-        if(getLogger()->debug()) {
-          getLogger()->debug("CUID#%s - It seems previously assigned segments"
-                             " are canceled. Restart.",
-                             util::itos(getCuid()).c_str());
-        }
+        A2_LOG_DEBUG(fmt("CUID#%s - It seems previously assigned segments"
+                         " are canceled. Restart.",
+                         util::itos(getCuid()).c_str()));
         // Request::isPipeliningEnabled() == true means aria2
         // accessed the remote server and discovered that the server
         // supports pipelining.
@@ -159,12 +154,10 @@ bool AbstractCommand::execute() {
          !getPieceStorage()->hasMissingUnusedPiece()) {
         SharedHandle<Request> fasterRequest = fileEntry_->findFasterRequest(req_);
         if(fasterRequest) {
-          if(getLogger()->info()) {
-            getLogger()->info("CUID#%s - Use faster Request hostname=%s, port=%u",
-                              util::itos(getCuid()).c_str(),
-                              fasterRequest->getHost().c_str(),
-                              fasterRequest->getPort());
-          }
+          A2_LOG_INFO(fmt("CUID#%s - Use faster Request hostname=%s, port=%u",
+                          util::itos(getCuid()).c_str(),
+                          fasterRequest->getHost().c_str(),
+                          fasterRequest->getPort()));
           // Cancel current Request object and use faster one.
           fileEntry_->removeRequest(req_);
           Command* command =
@@ -206,16 +199,12 @@ bool AbstractCommand::execute() {
             // TODO socket could be pooled here if pipelining is
             // enabled...  Hmm, I don't think if pipelining is enabled
             // it does not go here.
-            if(getLogger()->info()) {
-              getLogger()->info(MSG_NO_SEGMENT_AVAILABLE,
-                                util::itos(getCuid()).c_str());
-            }
+            A2_LOG_INFO(fmt(MSG_NO_SEGMENT_AVAILABLE,
+                            util::itos(getCuid()).c_str()));
             // When all segments are ignored in SegmentMan, there are
             // no URIs available, so don't retry.
             if(getSegmentMan()->allSegmentsIgnored()) {
-              if(getLogger()->debug()) {
-                getLogger()->debug("All segments are ignored.");
-              }
+              A2_LOG_DEBUG("All segments are ignored.");
               return true;
             } else {
               return prepareForRetry(1);
@@ -247,21 +236,17 @@ bool AbstractCommand::execute() {
                                                           req_->getProtocol());
         ss->setError();
         // Purging IP address cache to renew IP address.
-        if(getLogger()->debug()) {
-          getLogger()->debug("CUID#%s - Marking IP address %s as bad",
-                             util::itos(getCuid()).c_str(),
-                             req_->getConnectedAddr().c_str());
-        }
+        A2_LOG_DEBUG(fmt("CUID#%s - Marking IP address %s as bad",
+                         util::itos(getCuid()).c_str(),
+                         req_->getConnectedAddr().c_str()));
         e_->markBadIPAddress(req_->getConnectedHostname(),
                              req_->getConnectedAddr(),
                              req_->getConnectedPort());
         if(e_->findCachedIPAddress
            (req_->getConnectedHostname(), req_->getConnectedPort()).empty()) {
-          if(getLogger()->debug()) {
-            getLogger()->debug("CUID#%s - All IP addresses were marked bad."
-                               " Removing Entry.",
-                               util::itos(getCuid()).c_str());
-          }
+          A2_LOG_DEBUG(fmt("CUID#%s - All IP addresses were marked bad."
+                           " Removing Entry.",
+                           util::itos(getCuid()).c_str()));
           e_->removeCachedIPAddress
             (req_->getConnectedHostname(), req_->getConnectedPort());
         }
@@ -272,15 +257,13 @@ bool AbstractCommand::execute() {
     }
   } catch(DlAbortEx& err) {
     if(!req_) {
-      if(getLogger()->debug()) {
-        getLogger()->debug(EX_EXCEPTION_CAUGHT, err);
-      }
+      A2_LOG_DEBUG_EX(EX_EXCEPTION_CAUGHT, err);
     } else {
-      getLogger()->error
-        (MSG_DOWNLOAD_ABORTED,
-         DL_ABORT_EX2(StringFormat
-                      ("URI=%s", req_->getCurrentUri().c_str()).str(),err),
-         util::itos(getCuid()).c_str(), req_->getUri().c_str());
+      A2_LOG_ERROR_EX(fmt(MSG_DOWNLOAD_ABORTED,
+                          util::itos(getCuid()).c_str(),
+                          req_->getUri().c_str()),
+                      DL_ABORT_EX2(fmt("URI=%s", req_->getCurrentUri().c_str()),
+                                   err));
       fileEntry_->addURIResult(req_->getUri(), err.getCode());
       requestGroup_->setLastUriResult(req_->getUri(), err.getCode());
       if(err.getCode() == downloadresultcode::CANNOT_RESUME) {
@@ -292,27 +275,23 @@ bool AbstractCommand::execute() {
     return true;
   } catch(DlRetryEx& err) {
     assert(req_);
-    if(getLogger()->info()) {
-      getLogger()->info
-        (MSG_RESTARTING_DOWNLOAD,
-         DL_RETRY_EX2(StringFormat
-                      ("URI=%s", req_->getCurrentUri().c_str()).str(),
-                      err),
-         util::itos(getCuid()).c_str(), req_->getUri().c_str());
-    }
+    A2_LOG_INFO_EX(fmt(MSG_RESTARTING_DOWNLOAD,
+                       util::itos(getCuid()).c_str(), req_->getUri().c_str()),
+                   DL_RETRY_EX2(fmt("URI=%s", req_->getCurrentUri().c_str()),
+                                err));
     req_->addTryCount();
     req_->resetRedirectCount();
     req_->resetUri();
     const unsigned int maxTries = getOption()->getAsInt(PREF_MAX_TRIES);
     bool isAbort = maxTries != 0 && req_->getTryCount() >= maxTries;
     if(isAbort) {
-      if(getLogger()->info()) {
-        getLogger()->info(MSG_MAX_TRY,
-                          util::itos(getCuid()).c_str(), req_->getTryCount());
-      }
-      getLogger()->error(MSG_DOWNLOAD_ABORTED, err,
-                         util::itos(getCuid()).c_str(),
-                         req_->getUri().c_str());
+      A2_LOG_INFO(fmt(MSG_MAX_TRY,
+                      util::itos(getCuid()).c_str(),
+                      req_->getTryCount()));
+      A2_LOG_ERROR_EX(fmt(MSG_DOWNLOAD_ABORTED,
+                          util::itos(getCuid()).c_str(),
+                          req_->getUri().c_str()),
+                      err);
       fileEntry_->addURIResult(req_->getUri(), err.getCode());
       requestGroup_->setLastUriResult(req_->getUri(), err.getCode());
       if(err.getCode() == downloadresultcode::CANNOT_RESUME) {
@@ -325,7 +304,7 @@ bool AbstractCommand::execute() {
       return prepareForRetry(0);
     }
   } catch(DownloadFailureException& err) {
-    getLogger()->error(EX_EXCEPTION_CAUGHT, err);
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, err);
     if(req_) {
       fileEntry_->addURIResult(req_->getUri(), err.getCode());
       requestGroup_->setLastUriResult(req_->getUri(), err.getCode());
@@ -343,19 +322,15 @@ void AbstractCommand::tryReserved() {
     // and there are no URI left. Because file length is unknown, we
     // can assume that there are no in-flight request object.
     if(entry->getLength() == 0 && entry->getRemainingUris().empty()) {
-      if(getLogger()->debug()) {
-        getLogger()->debug("CUID#%s - Not trying next request."
-                           " No reserved/pooled request is remaining and"
-                           " total length is still unknown.",
-                           util::itos(getCuid()).c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - Not trying next request."
+                       " No reserved/pooled request is remaining and"
+                       " total length is still unknown.",
+                       util::itos(getCuid()).c_str()));
       return;
     }
   }
-  if(getLogger()->debug()) {
-    getLogger()->debug("CUID#%s - Trying reserved/pooled request.",
-                       util::itos(getCuid()).c_str());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - Trying reserved/pooled request.",
+                   util::itos(getCuid()).c_str()));
   std::vector<Command*> commands;
   requestGroup_->createNextCommand(commands, e_, 1);
   e_->setNoWait(true);
@@ -368,10 +343,8 @@ bool AbstractCommand::prepareForRetry(time_t wait) {
   }
   if(req_) {
     fileEntry_->poolRequest(req_);
-    if(getLogger()->debug()) {
-      getLogger()->debug("CUID#%s - Pooling request URI=%s",
-                         util::itos(getCuid()).c_str(), req_->getUri().c_str());
-    }
+    A2_LOG_DEBUG(fmt("CUID#%s - Pooling request URI=%s",
+                     util::itos(getCuid()).c_str(), req_->getUri().c_str()));
     if(getSegmentMan()) {
       getSegmentMan()->recognizeSegmentFor(fileEntry_);
     }
@@ -394,10 +367,8 @@ void AbstractCommand::onAbort() {
     fileEntry_->removeIdenticalURI(req_->getUri());
     fileEntry_->removeRequest(req_);
   }
-  if(getLogger()->debug()) {
-    getLogger()->debug("CUID#%s - Aborting download",
-                       util::itos(getCuid()).c_str());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - Aborting download",
+                   util::itos(getCuid()).c_str()));
   if(getPieceStorage()) {
     getSegmentMan()->cancelSegment(getCuid());
     // Don't do following process if BitTorrent is involved or files
@@ -414,14 +385,12 @@ void AbstractCommand::onAbort() {
         // Local file exists, but given servers(or at least contacted
         // ones) doesn't support resume. Let's restart download from
         // scratch.
-        getLogger()->notice("CUID#%s - Failed to resume download."
-                            " Download from scratch.",
-                            util::itos(getCuid()).c_str());
-        if(getLogger()->debug()) {
-          getLogger()->debug
-            ("CUID#%s - Gathering URIs that has CANNOT_RESUME error",
-             util::itos(getCuid()).c_str());
-        }
+        A2_LOG_NOTICE(fmt("CUID#%s - Failed to resume download."
+                          " Download from scratch.",
+                          util::itos(getCuid()).c_str()));
+        A2_LOG_DEBUG(fmt("CUID#%s - Gathering URIs that has CANNOT_RESUME"
+                         " error",
+                         util::itos(getCuid()).c_str()));
         // Set PREF_ALWAYS_RESUME to A2_V_TRUE to avoid repeating this
         // process.
         getOption()->put(PREF_ALWAYS_RESUME, A2_V_TRUE);
@@ -435,11 +404,9 @@ void AbstractCommand::onAbort() {
           uris.reserve(res.size());
           std::transform(res.begin(), res.end(), std::back_inserter(uris),
                          std::mem_fun_ref(&URIResult::getURI));
-          if(getLogger()->debug()) {
-            getLogger()->debug("CUID#%s - %lu URIs found.",
-                               util::itos(getCuid()).c_str(),
-                               static_cast<unsigned long int>(uris.size()));
-          }
+          A2_LOG_DEBUG(fmt("CUID#%s - %lu URIs found.",
+                           util::itos(getCuid()).c_str(),
+                           static_cast<unsigned long int>(uris.size())));
           fileEntry_->addUris(uris.begin(), uris.end());
           getSegmentMan()->recognizeSegmentFor(fileEntry_);
         }
@@ -640,15 +607,10 @@ SharedHandle<Request> AbstractCommand::createProxyRequest() const
   if(!proxy.empty()) {
     proxyRequest.reset(new Request());
     if(proxyRequest->setUri(proxy)) {
-      if(getLogger()->debug()) {
-        getLogger()->debug("CUID#%s - Using proxy",
-                           util::itos(getCuid()).c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - Using proxy", util::itos(getCuid()).c_str()));
     } else {
-      if(getLogger()->debug()) {
-        getLogger()->debug("CUID#%s - Failed to parse proxy string",
-                           util::itos(getCuid()).c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - Failed to parse proxy string",
+                       util::itos(getCuid()).c_str()));
       proxyRequest.reset();
     }
   }
@@ -671,10 +633,9 @@ void AbstractCommand::initAsyncNameResolver(const std::string& hostname)
     family = AF_INET;
   }
   asyncNameResolver_.reset(new AsyncNameResolver(family));
-  if(getLogger()->info()) {
-    getLogger()->info(MSG_RESOLVING_HOSTNAME,
-                      util::itos(getCuid()).c_str(), hostname.c_str());
-  }
+  A2_LOG_INFO(fmt(MSG_RESOLVING_HOSTNAME,
+                  util::itos(getCuid()).c_str(),
+                  hostname.c_str()));
   asyncNameResolver_->resolve(hostname);
   setNameResolverCheck(asyncNameResolver_);
 }
@@ -759,12 +720,10 @@ std::string AbstractCommand::resolveHostname
         }
         res.resolve(addrs, hostname);
       }
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_NAME_RESOLUTION_COMPLETE,
-                        util::itos(getCuid()).c_str(),
-                        hostname.c_str(),
-                        strjoin(addrs.begin(), addrs.end(), ", ").c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_NAME_RESOLUTION_COMPLETE,
+                    util::itos(getCuid()).c_str(),
+                    hostname.c_str(),
+                    strjoin(addrs.begin(), addrs.end(), ", ").c_str()));
     for(std::vector<std::string>::const_iterator i = addrs.begin(),
           eoi = addrs.end(); i != eoi; ++i) {
       e_->cacheIPAddress(hostname, *i, port);
@@ -772,11 +731,10 @@ std::string AbstractCommand::resolveHostname
     ipaddr = e_->findCachedIPAddress(hostname, port);
   } else {
     ipaddr = addrs.front();
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_DNS_CACHE_HIT,
-                        util::itos(getCuid()).c_str(), hostname.c_str(),
-                        strjoin(addrs.begin(), addrs.end(), ", ").c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_DNS_CACHE_HIT,
+                    util::itos(getCuid()).c_str(),
+                    hostname.c_str(),
+                    strjoin(addrs.begin(), addrs.end(), ", ").c_str()));
   }
   return ipaddr;
 }
@@ -804,11 +762,9 @@ bool AbstractCommand::checkIfConnectionEstablished
       // See also InitiateConnectionCommand::executeInternal()
       e_->markBadIPAddress(connectedHostname, connectedAddr, connectedPort);
       if(!e_->findCachedIPAddress(connectedHostname, connectedPort).empty()) {
-        if(getLogger()->info()) {
-          getLogger()->info(MSG_CONNECT_FAILED_AND_RETRY,
-                            util::itos(getCuid()).c_str(),
-                            connectedAddr.c_str(), connectedPort);
-        }
+        A2_LOG_INFO(fmt(MSG_CONNECT_FAILED_AND_RETRY,
+                        util::itos(getCuid()).c_str(),
+                        connectedAddr.c_str(), connectedPort));
         Command* command =
           InitiateConnectionCommandFactory::createInitiateConnectionCommand
           (getCuid(), req_, fileEntry_, requestGroup_, e_);
diff --git a/src/AbstractDiskWriter.cc b/src/AbstractDiskWriter.cc
index 2385f7a9..d8429cd6 100644
--- a/src/AbstractDiskWriter.cc
+++ b/src/AbstractDiskWriter.cc
@@ -47,8 +47,6 @@
 #include "File.h"
 #include "util.h"
 #include "message.h"
-#include "LogFactory.h"
-#include "Logger.h"
 #include "DlAbortEx.h"
 #include "a2io.h"
 #include "StringFormat.h"
@@ -56,12 +54,12 @@
 
 namespace aria2 {
 
-AbstractDiskWriter::AbstractDiskWriter(const std::string& filename):
-  filename_(filename),
-  fd_(-1),
-  readOnly_(false),
-  directIOAllowed_(false),
-  logger_(LogFactory::getInstance()) {}
+AbstractDiskWriter::AbstractDiskWriter(const std::string& filename)
+  : filename_(filename),
+    fd_(-1),
+    readOnly_(false),
+    directIOAllowed_(false)
+{}
 
 AbstractDiskWriter::~AbstractDiskWriter()
 {
diff --git a/src/AbstractDiskWriter.h b/src/AbstractDiskWriter.h
index ea7652c2..aa9de332 100644
--- a/src/AbstractDiskWriter.h
+++ b/src/AbstractDiskWriter.h
@@ -40,8 +40,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class AbstractDiskWriter : public DiskWriter {
 private:
   std::string filename_;
@@ -51,8 +49,6 @@ private:
 
   bool directIOAllowed_;
 
-  Logger* logger_;
-
   ssize_t writeDataInternal(const unsigned char* data, size_t len);
   ssize_t readDataInternal(unsigned char* data, size_t len);
 
diff --git a/src/ActivePeerConnectionCommand.cc b/src/ActivePeerConnectionCommand.cc
index e718c8bd..6b11e98b 100644
--- a/src/ActivePeerConnectionCommand.cc
+++ b/src/ActivePeerConnectionCommand.cc
@@ -41,6 +41,7 @@
 #include "BtRuntime.h"
 #include "Peer.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "prefs.h"
 #include "Option.h"
 #include "BtConstants.h"
@@ -51,6 +52,7 @@
 #include "bittorrent_helper.h"
 #include "wallclock.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -59,12 +61,11 @@ ActivePeerConnectionCommand::ActivePeerConnectionCommand
  RequestGroup* requestGroup,
  DownloadEngine* e,
  time_t interval)
-  :
-  Command(cuid),
-  requestGroup_(requestGroup),
-  interval_(interval),
-  e_(e),
-  numNewConnection_(5)
+  : Command(cuid),
+    requestGroup_(requestGroup),
+    interval_(interval),
+    e_(e),
+    numNewConnection_(5)
 {
   requestGroup_->increaseNumCommand();
 }
@@ -141,11 +142,9 @@ void ActivePeerConnectionCommand::connectToPeer(const SharedHandle<Peer>& peer)
   command->setPeerStorage(peerStorage_);
   command->setPieceStorage(pieceStorage_);
   e_->addCommand(command);
-  if(getLogger()->info()) {
-    getLogger()->info(MSG_CONNECTING_TO_PEER,
-                      util::itos(getCuid()).c_str(),
-                      peer->getIPAddress().c_str());
-  }
+  A2_LOG_INFO(fmt(MSG_CONNECTING_TO_PEER,
+                  util::itos(getCuid()).c_str(),
+                  peer->getIPAddress().c_str()));
 }
 
 void ActivePeerConnectionCommand::setBtRuntime
diff --git a/src/AdaptiveFileAllocationIterator.cc b/src/AdaptiveFileAllocationIterator.cc
index 347ae0df..8eeb5f99 100644
--- a/src/AdaptiveFileAllocationIterator.cc
+++ b/src/AdaptiveFileAllocationIterator.cc
@@ -45,9 +45,11 @@
 namespace aria2 {
 
 AdaptiveFileAllocationIterator::AdaptiveFileAllocationIterator
-(BinaryStream* stream, off_t offset, uint64_t totalLength):
-  stream_(stream), offset_(offset), totalLength_(totalLength),
-  logger_(LogFactory::getInstance()) {}
+(BinaryStream* stream, off_t offset, uint64_t totalLength)
+ : stream_(stream),
+   offset_(offset),
+   totalLength_(totalLength)
+{}
 
 AdaptiveFileAllocationIterator::~AdaptiveFileAllocationIterator() {}
 
@@ -56,23 +58,17 @@ void AdaptiveFileAllocationIterator::allocateChunk()
   if(!allocator_) {
 #ifdef HAVE_FALLOCATE
     try {
-      if(logger_->debug()) {
-        logger_->debug("Testing file system supports fallocate.");
-      }
+      A2_LOG_DEBUG("Testing file system supports fallocate.");
       if(static_cast<uint64_t>(offset_) < totalLength_) {
         off_t len = std::min(totalLength_-offset_, static_cast<uint64_t>(4096));
         stream_->allocate(offset_, len);
         offset_ += len;
       }
-      if(logger_->debug()) {
-        logger_->debug("File system supports fallocate.");
-      }
+      A2_LOG_DEBUG("File system supports fallocate.");
       allocator_.reset
         (new FallocFileAllocationIterator(stream_, offset_, totalLength_));
     } catch(RecoverableException& e) {
-      if(logger_->debug()) {
-        logger_->debug("File system does not support fallocate.");
-      }
+      A2_LOG_DEBUG("File system does not support fallocate.");
       SharedHandle<SingleFileAllocationIterator> salloc
         (new SingleFileAllocationIterator(stream_, offset_, totalLength_));
       salloc->init();
diff --git a/src/AdaptiveFileAllocationIterator.h b/src/AdaptiveFileAllocationIterator.h
index ac7d22a4..8a3f2e3b 100644
--- a/src/AdaptiveFileAllocationIterator.h
+++ b/src/AdaptiveFileAllocationIterator.h
@@ -40,7 +40,6 @@
 namespace aria2 {
 
 class BinaryStream;
-class Logger;
 
 class AdaptiveFileAllocationIterator:public FileAllocationIterator
 {
@@ -52,8 +51,6 @@ private:
   off_t offset_;
 
   uint64_t totalLength_;
-
-  Logger* logger_;
 public:
   AdaptiveFileAllocationIterator
   (BinaryStream* stream, off_t offset, uint64_t totalLength);
diff --git a/src/AdaptiveURISelector.cc b/src/AdaptiveURISelector.cc
index 16909e23..9a994549 100644
--- a/src/AdaptiveURISelector.cc
+++ b/src/AdaptiveURISelector.cc
@@ -44,6 +44,7 @@
 #include "ServerStatMan.h"
 #include "ServerStat.h"
 #include "RequestGroup.h"
+#include "Logger.h"
 #include "LogFactory.h"
 #include "A2STR.h"
 #include "prefs.h"
@@ -52,6 +53,7 @@
 #include "SocketCore.h"
 #include "FileEntry.h"
 #include "uri.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -63,10 +65,9 @@ namespace aria2 {
  */
 
 AdaptiveURISelector::AdaptiveURISelector
-(const SharedHandle<ServerStatMan>& serverStatMan, RequestGroup* requestGroup):
-  serverStatMan_(serverStatMan),
-  requestGroup_(requestGroup),
-  logger_(LogFactory::getInstance())
+(const SharedHandle<ServerStatMan>& serverStatMan, RequestGroup* requestGroup)
+  : serverStatMan_(serverStatMan),
+    requestGroup_(requestGroup)
 {
   resetCounters();
 }
@@ -77,10 +78,8 @@ std::string AdaptiveURISelector::select
 (FileEntry* fileEntry,
  const std::vector<std::pair<size_t, std::string> >& usedHosts)
 {
-  if(logger_->debug()) {
-    logger_->debug("AdaptiveURISelector: called %d",
-                   requestGroup_->getNumConnection());
-  }
+  A2_LOG_DEBUG(fmt("AdaptiveURISelector: called %d",
+                   requestGroup_->getNumConnection()));
   std::deque<std::string>& uris = fileEntry->getRemainingUris();
   if (uris.empty() && requestGroup_->getNumConnection() <= 1) {
     // here we know the download will fail, trying to find previously
@@ -108,13 +107,13 @@ void AdaptiveURISelector::mayRetryWithIncreasedTimeout(FileEntry* fileEntry)
   std::transform(timeouts.begin(), timeouts.end(), std::back_inserter(uris),
                  std::mem_fun_ref(&URIResult::getURI));
 
-  if(logger_->debug()) {
+  if(A2_LOG_DEBUG_ENABLED) {
     for(std::deque<std::string>::const_iterator i = uris.begin(),
           eoi = uris.end(); i != eoi; ++i) {
-      logger_->debug("AdaptiveURISelector: will retry server with increased"
-                     " timeout (%ld s): %s",
-                     static_cast<long int>(requestGroup_->getTimeout()),
-                     (*i).c_str());
+      A2_LOG_DEBUG(fmt("AdaptiveURISelector: will retry server with increased"
+                       " timeout (%ld s): %s",
+                       static_cast<long int>(requestGroup_->getTimeout()),
+                       (*i).c_str()));
     }
   }
 }
@@ -140,10 +139,9 @@ std::string AdaptiveURISelector::selectOne(const std::deque<std::string>& uris)
     if(getNbTestedServers(uris) < 3) {
       std::string notTested = getFirstNotTestedUri(uris);
       if(notTested != A2STR::NIL) {
-        if(logger_->debug()) {
-          logger_->debug("AdaptiveURISelector: choosing the first non tested"
-                         " mirror: %s", notTested.c_str());
-        }
+        A2_LOG_DEBUG(fmt("AdaptiveURISelector: choosing the first non tested"
+                         " mirror: %s",
+                         notTested.c_str()));
         --nbServerToEvaluate_;
         return notTested;
       }
@@ -154,21 +152,17 @@ std::string AdaptiveURISelector::selectOne(const std::deque<std::string>& uris)
       std::string notTested = getFirstNotTestedUri(uris);
       if(notTested != A2STR::NIL) {
         /* Here we return the first untested mirror */
-        if(logger_->debug()) {
-          logger_->debug("AdaptiveURISelector: choosing non tested mirror %s"
+        A2_LOG_DEBUG(fmt("AdaptiveURISelector: choosing non tested mirror %s"
                          " for connection #%d",
-                         notTested.c_str(), nbConnections_);
-        }
+                         notTested.c_str(), nbConnections_));
         return notTested;
       } else {
         /* Here we return a mirror which need to be tested again */
         std::string toReTest = getFirstToTestUri(uris);
         if(toReTest != A2STR::NIL) {
-          if(logger_->debug()) {
-            logger_->debug("AdaptiveURISelector: choosing mirror %s which has"
+          A2_LOG_DEBUG(fmt("AdaptiveURISelector: choosing mirror %s which has"
                            " not been tested recently for connection #%d",
-                           toReTest.c_str(), nbConnections_);
-          }
+                           toReTest.c_str(), nbConnections_));
           return toReTest;
         } else {
           return getBestMirror(uris);
@@ -191,19 +185,18 @@ std::string AdaptiveURISelector::getBestMirror
   
   if (bests.size() < 2) {
     std::string uri = getMaxDownloadSpeedUri(uris);
-    if(logger_->debug()) {
-      logger_->debug("AdaptiveURISelector: choosing the best mirror :"
+    A2_LOG_DEBUG(fmt("AdaptiveURISelector: choosing the best mirror :"
                      " %.2fKB/s %s (other mirrors are at least 25%% slower)",
-                     (float) max/1024, uri.c_str());
-    }
+                     (float) max/1024,
+                     uri.c_str()));
     return uri;
   } else {
     std::string uri = selectRandomUri(bests);
-    if(logger_->debug()) {
-      logger_->debug("AdaptiveURISelector: choosing randomly one of the best"
+    A2_LOG_DEBUG(fmt("AdaptiveURISelector: choosing randomly one of the best"
                      " mirrors (range [%.2fKB/s, %.2fKB/s]): %s",
-                     (float) min/1024, (float) max/1024, uri.c_str());
-    }
+                     (float) min/1024,
+                     (float) max/1024,
+                     uri.c_str()));
     return uri;
   }
 }
@@ -230,12 +223,17 @@ void AdaptiveURISelector::adjustLowestSpeedLimit
     unsigned int low_lowest = 4 * 1024;
     unsigned int max = getMaxDownloadSpeed(uris);
     if (max > 0 && lowest > max / 4) {
-      logger_->notice("Lowering lowest-speed-limit since known max speed is too"
-                      " near (new:%d was:%d max:%d)", max / 4, lowest, max);
+      A2_LOG_NOTICE(fmt("Lowering lowest-speed-limit since known max speed is"
+                        " too near (new:%d was:%d max:%d)",
+                        max / 4,
+                        lowest,
+                        max));
       command->setLowestDownloadSpeedLimit(max / 4);
     } else if (max == 0 && lowest > low_lowest) {
-      logger_->notice("Lowering lowest-speed-limit since we have no clue about"
-                      " available speed (now:%d was:%d)", low_lowest, lowest);
+      A2_LOG_NOTICE(fmt("Lowering lowest-speed-limit since we have no clue"
+                        " about available speed (now:%d was:%d)",
+                        low_lowest,
+                        lowest));
       command->setLowestDownloadSpeedLimit(low_lowest);
     }
   }
diff --git a/src/AdaptiveURISelector.h b/src/AdaptiveURISelector.h
index 97f7bcf9..b8ac6b75 100644
--- a/src/AdaptiveURISelector.h
+++ b/src/AdaptiveURISelector.h
@@ -43,7 +43,6 @@ namespace aria2 {
 class ServerStatMan;
 class RequestGroup;
 class ServerStat;
-class Logger;
 
 class AdaptiveURISelector:public URISelector {
 private:
@@ -55,8 +54,6 @@ private:
 
   static const time_t MAX_TIMEOUT = 60;
 
-  Logger* logger_;
-
   void mayRetryWithIncreasedTimeout(FileEntry* fileEntry);
 
   std::string selectOne(const std::deque<std::string>& uris);
diff --git a/src/BtDependency.cc b/src/BtDependency.cc
index 8eb6dd8d..47ae8516 100644
--- a/src/BtDependency.cc
+++ b/src/BtDependency.cc
@@ -48,15 +48,17 @@
 #include "bittorrent_helper.h"
 #include "DlAbortEx.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "FileEntry.h"
 
 namespace aria2 {
 
-BtDependency::BtDependency(RequestGroup* dependant,
-                           const SharedHandle<RequestGroup>& dependee):
-  dependant_(dependant),
-  dependee_(dependee),
-  logger_(LogFactory::getInstance()) {}
+BtDependency::BtDependency
+(RequestGroup* dependant,
+ const SharedHandle<RequestGroup>& dependee)
+  : dependant_(dependant),
+    dependee_(dependee)
+{}
 
 BtDependency::~BtDependency() {}
 
@@ -136,27 +138,21 @@ bool BtDependency::resolve()
         }
       }
     } catch(RecoverableException& e) {
-      logger_->error(EX_EXCEPTION_CAUGHT, e);
-      if(logger_->info()) {
-        logger_->info("BtDependency for GID#%s failed. Go without Bt.",
-                      util::itos(dependant_->getGID()).c_str());
-      }
+      A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
+      A2_LOG_INFO(fmt("BtDependency for GID#%s failed. Go without Bt.",
+                      util::itos(dependant_->getGID()).c_str()));
       return true;
     }
-    if(logger_->info()) {
-      logger_->info("Dependency resolved for GID#%s",
-                    util::itos(dependant_->getGID()).c_str());
-    }
+    A2_LOG_INFO(fmt("Dependency resolved for GID#%s",
+                    util::itos(dependant_->getGID()).c_str()));
     dependant_->setDownloadContext(context);
     return true;
   } else if(dependee_->getNumCommand() == 0) {
     // dependee_'s download failed.
     // cut reference here
     dependee_.reset();
-    if(logger_->info()) {
-      logger_->info("BtDependency for GID#%s failed. Go without Bt.",
-                    util::itos(dependant_->getGID()).c_str());
-    }
+    A2_LOG_INFO(fmt("BtDependency for GID#%s failed. Go without Bt.",
+                    util::itos(dependant_->getGID()).c_str()));
     return true;
   } else {
     return false;
diff --git a/src/BtDependency.h b/src/BtDependency.h
index 32fe45ad..79bf77d2 100644
--- a/src/BtDependency.h
+++ b/src/BtDependency.h
@@ -41,14 +41,12 @@ namespace aria2 {
 
 class RequestGroup;
 class Option;
-class Logger;
 
 class BtDependency : public Dependency
 {
 private:
   RequestGroup* dependant_;
   SharedHandle<RequestGroup> dependee_;
-  Logger* logger_;
 public:
   BtDependency(RequestGroup* dependant,
                const SharedHandle<RequestGroup>& dependee);
diff --git a/src/BtLeecherStateChoke.cc b/src/BtLeecherStateChoke.cc
index 361a3412..0088f825 100644
--- a/src/BtLeecherStateChoke.cc
+++ b/src/BtLeecherStateChoke.cc
@@ -41,13 +41,14 @@
 #include "LogFactory.h"
 #include "SimpleRandomizer.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-BtLeecherStateChoke::BtLeecherStateChoke():
-  round_(0),
-  lastRound_(0),
-  logger_(LogFactory::getInstance()) {}
+BtLeecherStateChoke::BtLeecherStateChoke()
+  : round_(0),
+    lastRound_(0)
+{}
 
 BtLeecherStateChoke::~BtLeecherStateChoke() {}
 
@@ -142,8 +143,8 @@ void BtLeecherStateChoke::plannedOptimisticUnchoke
     std::random_shuffle(peerEntries.begin(), i,
                         *(SimpleRandomizer::getInstance().get()));
     (*peerEntries.begin()).enableOptUnchoking();
-    logger_->info
-      ("POU: %s", (*peerEntries.begin()).getPeer()->getIPAddress().c_str());
+    A2_LOG_INFO(fmt("POU: %s",
+                    (*peerEntries.begin()).getPeer()->getIPAddress().c_str()));
   }
 }
 
@@ -162,9 +163,9 @@ void BtLeecherStateChoke::regularUnchoke(std::vector<PeerEntry>& peerEntries)
   std::vector<PeerEntry>::iterator peerIter = peerEntries.begin();
   for(;peerIter != rest && count; ++peerIter, --count) {
     (*peerIter).disableChokingRequired();
-    logger_->info("RU: %s, dlspd=%u",
-                  (*peerIter).getPeer()->getIPAddress().c_str(),
-                  (*peerIter).getDownloadSpeed());
+    A2_LOG_INFO(fmt("RU: %s, dlspd=%u",
+                    (*peerIter).getPeer()->getIPAddress().c_str(),
+                    (*peerIter).getDownloadSpeed()));
     if((*peerIter).getPeer()->optUnchoking()) {
       fastOptUnchoker = true;
       (*peerIter).disableOptUnchoking();
@@ -177,11 +178,11 @@ void BtLeecherStateChoke::regularUnchoke(std::vector<PeerEntry>& peerEntries)
           eoi = peerEntries.end(); i != eoi; ++i) {
       if((*i).getPeer()->peerInterested()) {
         (*i).enableOptUnchoking();
-        logger_->info("OU: %s", (*i).getPeer()->getIPAddress().c_str());
+        A2_LOG_INFO(fmt("OU: %s", (*i).getPeer()->getIPAddress().c_str()));
         break;
       } else {
         (*i).disableChokingRequired();
-        logger_->info("OU: %s", (*i).getPeer()->getIPAddress().c_str());
+        A2_LOG_INFO(fmt("OU: %s", (*i).getPeer()->getIPAddress().c_str()));
       }
     }
   }
@@ -191,7 +192,7 @@ void
 BtLeecherStateChoke::executeChoke
 (const std::vector<SharedHandle<Peer> >& peerSet)
 {
-  logger_->info("Leecher state, %d choke round started", round_);
+  A2_LOG_INFO(fmt("Leecher state, %d choke round started", round_));
   lastRound_ = global::wallclock;
 
   std::vector<PeerEntry> peerEntries;
diff --git a/src/BtLeecherStateChoke.h b/src/BtLeecherStateChoke.h
index db22e23a..80a3b9a0 100644
--- a/src/BtLeecherStateChoke.h
+++ b/src/BtLeecherStateChoke.h
@@ -45,7 +45,6 @@
 namespace aria2 {
 
 class Peer;
-class Logger;
 
 class BtLeecherStateChoke {
 private:
@@ -53,8 +52,6 @@ private:
 
   Timer lastRound_;
 
-  Logger* logger_;
-
   class PeerEntry {
   private:
     SharedHandle<Peer> peer_;
diff --git a/src/BtPieceMessage.cc b/src/BtPieceMessage.cc
index 7f76c209..0c072452 100644
--- a/src/BtPieceMessage.cc
+++ b/src/BtPieceMessage.cc
@@ -45,6 +45,7 @@
 #include "MessageDigestHelper.h"
 #include "DiskAdaptor.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "Peer.h"
 #include "Piece.h"
 #include "PieceStorage.h"
@@ -53,6 +54,7 @@
 #include "BtRequestFactory.h"
 #include "PeerConnection.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "DownloadContext.h"
 
 namespace aria2 {
@@ -60,13 +62,13 @@ namespace aria2 {
 const std::string BtPieceMessage::NAME("piece");
 
 BtPieceMessage::BtPieceMessage
-(size_t index, uint32_t begin, size_t blockLength):
-  AbstractBtMessage(ID, NAME),
-  index_(index),
-  begin_(begin),
-  blockLength_(blockLength),
-  block_(0),
-  rawData_(0)
+(size_t index, uint32_t begin, size_t blockLength)
+  : AbstractBtMessage(ID, NAME),
+    index_(index),
+    begin_(begin),
+    blockLength_(blockLength),
+    block_(0),
+    rawData_(0)
 {
   setUploading(true);
 }
@@ -107,22 +109,19 @@ void BtPieceMessage::doReceivedAction()
     getPeer()->snubbing(false);
     SharedHandle<Piece> piece = getPieceStorage()->getPiece(index_);
     off_t offset = (off_t)index_*downloadContext_->getPieceLength()+begin_;
-    if(getLogger()->debug()) {
-      getLogger()->debug(MSG_PIECE_RECEIVED,
-                         util::itos(getCuid()).c_str(),
-                         static_cast<unsigned long>(index_),
-                         begin_, blockLength_,
-                         static_cast<long long int>(offset),
-                         static_cast<unsigned long>(slot.getBlockIndex()));
-    }
+    A2_LOG_DEBUG(fmt(MSG_PIECE_RECEIVED,
+                     util::itos(getCuid()).c_str(),
+                     static_cast<unsigned long>(index_),
+                     begin_,
+                     blockLength_,
+                     static_cast<long long int>(offset),
+                     static_cast<unsigned long>(slot.getBlockIndex())));
     getPieceStorage()->getDiskAdaptor()->writeData
       (block_, blockLength_, offset);
     piece->completeBlock(slot.getBlockIndex());
-    if(getLogger()->debug()) {
-      getLogger()->debug(MSG_PIECE_BITFIELD, util::itos(getCuid()).c_str(),
-                         util::toHex(piece->getBitfield(),
-                                     piece->getBitfieldLength()).c_str());
-    }
+    A2_LOG_DEBUG(fmt(MSG_PIECE_BITFIELD, util::itos(getCuid()).c_str(),
+                     util::toHex(piece->getBitfield(),
+                                 piece->getBitfieldLength()).c_str()));
     piece->updateHash(begin_, block_, blockLength_);
     getBtMessageDispatcher()->removeOutstandingRequest(slot);
     if(piece->pieceComplete()) {
@@ -134,11 +133,10 @@ void BtPieceMessage::doReceivedAction()
       }
     }
   } else {
-    if(getLogger()->debug()) {
-      getLogger()->debug("CUID#%s - RequestSlot not found, index=%lu, begin=%u",
-                         util::itos(getCuid()).c_str(),
-                         static_cast<unsigned long>(index_), begin_);
-    }
+    A2_LOG_DEBUG(fmt("CUID#%s - RequestSlot not found, index=%lu, begin=%u",
+                     util::itos(getCuid()).c_str(),
+                     static_cast<unsigned long>(index_),
+                     begin_));
   }
 }
 
@@ -173,19 +171,15 @@ void BtPieceMessage::send()
   }
   size_t writtenLength;
   if(!isSendingInProgress()) {
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_SEND_PEER_MESSAGE,
-                        util::itos(getCuid()).c_str(),
-                        getPeer()->getIPAddress().c_str(),
-                        getPeer()->getPort(),
-                        toString().c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SEND_PEER_MESSAGE,
+                    util::itos(getCuid()).c_str(),
+                    getPeer()->getIPAddress().c_str(),
+                    getPeer()->getPort(),
+                    toString().c_str()));
     unsigned char* msgHdr = createMessageHeader();
     size_t msgHdrLen = getMessageHeaderLength();
-    if(getLogger()->debug()) {
-      getLogger()->debug("msglength = %lu bytes",
-                         static_cast<unsigned long>(msgHdrLen+blockLength_));
-    }
+    A2_LOG_DEBUG(fmt("msglength = %lu bytes",
+                     static_cast<unsigned long>(msgHdrLen+blockLength_)));
     getPeerConnection()->pushBytes(msgHdr, msgHdrLen);
     getPeerConnection()->sendPendingData();
     off_t pieceDataOffset =
@@ -226,10 +220,8 @@ std::string BtPieceMessage::toString() const
 bool BtPieceMessage::checkPieceHash(const SharedHandle<Piece>& piece)
 {
   if(!getPieceStorage()->isEndGame() && piece->isHashCalculated()) {
-    if(getLogger()->debug()) {
-      getLogger()->debug("Hash is available!! index=%lu",
-                         static_cast<unsigned long>(piece->getIndex()));
-    }
+    A2_LOG_DEBUG(fmt("Hash is available!! index=%lu",
+                     static_cast<unsigned long>(piece->getIndex())));
     return
       piece->getHashString()==downloadContext_->getPieceHash(piece->getIndex());
   } else {
@@ -243,22 +235,18 @@ bool BtPieceMessage::checkPieceHash(const SharedHandle<Piece>& piece)
 
 void BtPieceMessage::onNewPiece(const SharedHandle<Piece>& piece)
 {
-  if(getLogger()->info()) {
-    getLogger()->info(MSG_GOT_NEW_PIECE,
-                      util::itos(getCuid()).c_str(),
-                      static_cast<unsigned long>(piece->getIndex()));
-  }
+  A2_LOG_INFO(fmt(MSG_GOT_NEW_PIECE,
+                  util::itos(getCuid()).c_str(),
+                  static_cast<unsigned long>(piece->getIndex())));
   getPieceStorage()->completePiece(piece);
   getPieceStorage()->advertisePiece(getCuid(), piece->getIndex());
 }
 
 void BtPieceMessage::onWrongPiece(const SharedHandle<Piece>& piece)
 {
-  if(getLogger()->info()) {
-    getLogger()->info(MSG_GOT_WRONG_PIECE,
-                      util::itos(getCuid()).c_str(),
-                      static_cast<unsigned long>(piece->getIndex()));
-  }
+  A2_LOG_INFO(fmt(MSG_GOT_WRONG_PIECE,
+                  util::itos(getCuid()).c_str(),
+                  static_cast<unsigned long>(piece->getIndex())));
   erasePieceOnDisk(piece);
   piece->clearAllBlock();
   piece->destroyHashContext();
@@ -286,12 +274,11 @@ void BtPieceMessage::onChokingEvent(const BtChokingEvent& event)
   if(!isInvalidate() &&
      !isSendingInProgress() &&
      !getPeer()->isInAmAllowedIndexSet(index_)) {
-    if(getLogger()->debug()) {
-      getLogger()->debug(MSG_REJECT_PIECE_CHOKED,
-                         util::itos(getCuid()).c_str(),
-                         static_cast<unsigned long>(index_),
-                         begin_, blockLength_);
-    }
+    A2_LOG_DEBUG(fmt(MSG_REJECT_PIECE_CHOKED,
+                     util::itos(getCuid()).c_str(),
+                     static_cast<unsigned long>(index_),
+                     begin_,
+                     blockLength_));
     if(getPeer()->isFastExtensionEnabled()) {
       BtMessageHandle rej =
         getBtMessageFactory()->createRejectMessage
@@ -310,12 +297,11 @@ void BtPieceMessage::onCancelSendingPieceEvent
      index_ == event.getIndex() &&
      begin_ == event.getBegin() &&
      blockLength_ == event.getLength()) {
-    if(getLogger()->debug()) {
-      getLogger()->debug(MSG_REJECT_PIECE_CANCEL,
-                         util::itos(getCuid()).c_str(),
-                         static_cast<unsigned long>(index_),
-                         begin_, blockLength_);
-    }
+    A2_LOG_DEBUG(fmt(MSG_REJECT_PIECE_CANCEL,
+                     util::itos(getCuid()).c_str(),
+                     static_cast<unsigned long>(index_),
+                     begin_,
+                     blockLength_));
     if(getPeer()->isFastExtensionEnabled()) {
       BtMessageHandle rej =
         getBtMessageFactory()->createRejectMessage
diff --git a/src/BtPortMessage.cc b/src/BtPortMessage.cc
index b66cb5c2..e726017d 100644
--- a/src/BtPortMessage.cc
+++ b/src/BtPortMessage.cc
@@ -38,6 +38,7 @@
 #include "util.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "Peer.h"
 #include "DHTNode.h"
 #include "DHTRoutingTable.h"
@@ -45,19 +46,21 @@
 #include "DHTTaskFactory.h"
 #include "DHTTask.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "a2functional.h"
 
 namespace aria2 {
 
 const std::string BtPortMessage::NAME("port");
 
-BtPortMessage::BtPortMessage(uint16_t port):
-  SimpleBtMessage(ID, NAME), port_(port),
-  localNode_(0),
-  routingTable_(0),
-  taskQueue_(0),
-  taskFactory_(0)
- {}
+BtPortMessage::BtPortMessage(uint16_t port)
+  : SimpleBtMessage(ID, NAME),
+    port_(port),
+    localNode_(0),
+    routingTable_(0),
+    taskQueue_(0),
+    taskFactory_(0)
+{}
 
 SharedHandle<BtPortMessage> BtPortMessage::create
 (const unsigned char* data, size_t dataLength)
@@ -73,9 +76,7 @@ void BtPortMessage::doReceivedAction()
 {
   if(taskFactory_ && taskQueue_) {
     if(port_ == 0) {
-      if(getLogger()->debug()) {
-        getLogger()->debug("Ignored port 0.");
-      }
+      A2_LOG_DEBUG("Ignored port 0.");
       return;
     }
     // node id is random at this point. When ping reply received, new DHTNode
@@ -89,12 +90,12 @@ void BtPortMessage::doReceivedAction()
     }
     if(routingTable_->countBucket() == 1) {
       // initiate bootstrap
-      getLogger()->info("Dispatch node_lookup since too few buckets.");
+      A2_LOG_INFO("Dispatch node_lookup since too few buckets.");
       taskQueue_->addImmediateTask
         (taskFactory_->createNodeLookupTask(localNode_->getID()));
     }
   } else {
-    getLogger()->info
+    A2_LOG_INFO
       ("DHT port message received while localhost didn't declare support it.");
   }
 }
diff --git a/src/BtPostDownloadHandler.cc b/src/BtPostDownloadHandler.cc
index 6baace05..00ecea28 100644
--- a/src/BtPostDownloadHandler.cc
+++ b/src/BtPostDownloadHandler.cc
@@ -37,6 +37,7 @@
 #include "RequestGroup.h"
 #include "Option.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "DownloadHandlerConstants.h"
 #include "File.h"
 #include "PieceStorage.h"
@@ -46,6 +47,7 @@
 #include "Exception.h"
 #include "DownloadContext.h"
 #include "download_helper.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -66,8 +68,8 @@ void BtPostDownloadHandler::getNextRequestGroups
 (std::vector<SharedHandle<RequestGroup> >& groups,
  RequestGroup* requestGroup)
 {
-  getLogger()->info("Generating RequestGroups for Torrent file %s",
-                    requestGroup->getFirstFilePath().c_str());
+  A2_LOG_INFO(fmt("Generating RequestGroups for Torrent file %s",
+                  requestGroup->getFirstFilePath().c_str()));
   std::string content;
   try {
     requestGroup->getPieceStorage()->getDiskAdaptor()->openExistingFile();
diff --git a/src/BtSeederStateChoke.cc b/src/BtSeederStateChoke.cc
index ca062a02..c465b346 100644
--- a/src/BtSeederStateChoke.cc
+++ b/src/BtSeederStateChoke.cc
@@ -41,13 +41,14 @@
 #include "LogFactory.h"
 #include "SimpleRandomizer.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-BtSeederStateChoke::BtSeederStateChoke():
-  round_(0),
-  lastRound_(0),
-  logger_(LogFactory::getInstance()) {}
+BtSeederStateChoke::BtSeederStateChoke()
+  : round_(0),
+    lastRound_(0)
+{}
 
 BtSeederStateChoke::~BtSeederStateChoke() {}
 
@@ -123,8 +124,9 @@ void BtSeederStateChoke::unchoke
   for(std::vector<PeerEntry>::iterator eoi = peers.end();
       r != eoi && count; ++r, --count) {
     (*r).getPeer()->chokingRequired(false);
-    logger_->info("RU: %s, ulspd=%u", (*r).getPeer()->getIPAddress().c_str(),
-                  (*r).getUploadSpeed());
+    A2_LOG_INFO(fmt("RU: %s, ulspd=%u",
+                    (*r).getPeer()->getIPAddress().c_str(),
+                    (*r).getUploadSpeed()));
   }
 
   if(round_ < 2) {
@@ -134,7 +136,7 @@ void BtSeederStateChoke::unchoke
       std::random_shuffle(r, peers.end(),
                           *(SimpleRandomizer::getInstance().get()));
       (*r).getPeer()->optUnchoking(true);
-      logger_->info("POU: %s", (*r).getPeer()->getIPAddress().c_str());
+      A2_LOG_INFO(fmt("POU: %s", (*r).getPeer()->getIPAddress().c_str()));
     }
   }
 }
@@ -153,7 +155,7 @@ void
 BtSeederStateChoke::executeChoke
 (const std::vector<SharedHandle<Peer> >& peerSet)
 {
-  logger_->info("Seeder state, %d choke round started", round_);
+  A2_LOG_INFO(fmt("Seeder state, %d choke round started", round_));
   lastRound_ = global::wallclock;
 
   std::vector<PeerEntry> peerEntries;
diff --git a/src/BtSeederStateChoke.h b/src/BtSeederStateChoke.h
index 9c30fb92..d6b3da14 100644
--- a/src/BtSeederStateChoke.h
+++ b/src/BtSeederStateChoke.h
@@ -45,7 +45,6 @@
 namespace aria2 {
 
 class Peer;
-class Logger;
 
 class BtSeederStateChoke {
 private:
@@ -53,8 +52,6 @@ private:
 
   Timer lastRound_;
 
-  Logger* logger_;
-
   class PeerEntry {
   private:
     SharedHandle<Peer> peer_;
diff --git a/src/BtSetup.cc b/src/BtSetup.cc
index 6943a5c6..2851c9a5 100644
--- a/src/BtSetup.cc
+++ b/src/BtSetup.cc
@@ -83,10 +83,11 @@
 #include "DownloadContext.h"
 #include "PieceStorage.h"
 #include "PeerStorage.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-BtSetup::BtSetup():logger_(LogFactory::getInstance()) {}
+BtSetup::BtSetup() {}
 
 void BtSetup::setup(std::vector<Command*>& commands,
                     RequestGroup* requestGroup,
@@ -221,7 +222,7 @@ void BtSetup::setup(std::vector<Command*>& commands,
   if(option->getAsBool(PREF_BT_ENABLE_LPD) &&
      (metadataGetMode || !torrentAttrs->privateTorrent)) {
     if(LpdReceiveMessageCommand::getNumInstance() == 0) {
-      logger_->info("Initializing LpdMessageReceiver.");
+      A2_LOG_INFO("Initializing LpdMessageReceiver.");
       SharedHandle<LpdMessageReceiver> receiver
         (new LpdMessageReceiver(LPD_MULTICAST_ADDR, LPD_MULTICAST_PORT));
       bool initialized = false;
@@ -245,15 +246,15 @@ void BtSetup::setup(std::vector<Command*>& commands,
         }
       }
       if(initialized) {
-        logger_->info("LpdMessageReceiver initialized. multicastAddr=%s:%u,"
-                      " localAddr=%s",
-                      LPD_MULTICAST_ADDR, LPD_MULTICAST_PORT,
-                      receiver->getLocalAddress().c_str());
+        A2_LOG_INFO(fmt("LpdMessageReceiver initialized. multicastAddr=%s:%u,"
+                        " localAddr=%s",
+                        LPD_MULTICAST_ADDR, LPD_MULTICAST_PORT,
+                        receiver->getLocalAddress().c_str()));
         LpdReceiveMessageCommand* cmd =
           LpdReceiveMessageCommand::getInstance(e, receiver);
         e->addCommand(cmd);
       } else {
-        logger_->info("LpdMessageReceiver not initialized.");
+        A2_LOG_INFO("LpdMessageReceiver not initialized.");
       }
     }
     if(LpdReceiveMessageCommand::getNumInstance()) {
@@ -261,20 +262,20 @@ void BtSetup::setup(std::vector<Command*>& commands,
         bittorrent::getInfoHash(requestGroup->getDownloadContext());
       SharedHandle<LpdMessageReceiver> receiver =
         LpdReceiveMessageCommand::getInstance()->getLpdMessageReceiver();
-      logger_->info("Initializing LpdMessageDispatcher.");      
+      A2_LOG_INFO("Initializing LpdMessageDispatcher.");      
       SharedHandle<LpdMessageDispatcher> dispatcher
         (new LpdMessageDispatcher
          (std::string(&infoHash[0], &infoHash[INFO_HASH_LENGTH]),
           btRuntime->getListenPort(),
           LPD_MULTICAST_ADDR, LPD_MULTICAST_PORT));
       if(dispatcher->init(receiver->getLocalAddress(), /*ttl*/1, /*loop*/0)) {
-        logger_->info("LpdMessageDispatcher initialized.");      
+        A2_LOG_INFO("LpdMessageDispatcher initialized.");      
         LpdDispatchMessageCommand* cmd =
           new LpdDispatchMessageCommand(e->newCUID(), dispatcher, e);
         cmd->setBtRuntime(btRuntime);
         e->addCommand(cmd);
       } else {
-        logger_->info("LpdMessageDispatcher not initialized.");
+        A2_LOG_INFO("LpdMessageDispatcher not initialized.");
       }
     }
   }
diff --git a/src/BtSetup.h b/src/BtSetup.h
index 0cbf1306..e44dea69 100644
--- a/src/BtSetup.h
+++ b/src/BtSetup.h
@@ -40,15 +40,12 @@
 
 namespace aria2 {
 
-class Logger;
 class RequestGroup;
 class DownloadEngine;
 class Option;
 class Command;
 
 class BtSetup {
-private:
-  Logger* logger_;
 public:
   BtSetup();
 
diff --git a/src/BtStopDownloadCommand.cc b/src/BtStopDownloadCommand.cc
index aaa47627..59225080 100644
--- a/src/BtStopDownloadCommand.cc
+++ b/src/BtStopDownloadCommand.cc
@@ -37,8 +37,10 @@
 #include "RequestGroup.h"
 #include "BtRuntime.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "wallclock.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -46,10 +48,10 @@ BtStopDownloadCommand::BtStopDownloadCommand
 (cuid_t cuid,
  RequestGroup* requestGroup,
  DownloadEngine* e,
- time_t timeout):
-  TimeBasedCommand(cuid, e, 1),
-  requestGroup_(requestGroup),
-  timeout_(timeout)
+ time_t timeout)
+  : TimeBasedCommand(cuid, e, 1),
+    requestGroup_(requestGroup),
+    timeout_(timeout)
 {}
 
 void BtStopDownloadCommand::preProcess()
@@ -58,9 +60,9 @@ void BtStopDownloadCommand::preProcess()
     enableExit();
   }
   if(checkPoint_.difference(global::wallclock) >= timeout_) {
-    getLogger()->notice("GID#%s Stop downloading torrent due to"
-                        " --bt-stop-timeout option.",
-                        util::itos(requestGroup_->getGID()).c_str());
+    A2_LOG_NOTICE(fmt("GID#%s Stop downloading torrent due to"
+                      " --bt-stop-timeout option.",
+                      util::itos(requestGroup_->getGID()).c_str()));
     requestGroup_->setForceHaltRequested(true);
     enableExit();
   }
diff --git a/src/CheckIntegrityCommand.cc b/src/CheckIntegrityCommand.cc
index a9c0ff8d..8a36dddd 100644
--- a/src/CheckIntegrityCommand.cc
+++ b/src/CheckIntegrityCommand.cc
@@ -37,12 +37,14 @@
 #include "DownloadEngine.h"
 #include "RequestGroup.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "message.h"
 #include "prefs.h"
 #include "DownloadContext.h"
 #include "a2functional.h"
 #include "RecoverableException.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -69,18 +71,18 @@ bool CheckIntegrityCommand::executeInternal()
     // needed.
     getRequestGroup()->enableSaveControlFile();
     if(getRequestGroup()->downloadFinished()) {
-      getLogger()->notice
-        (MSG_VERIFICATION_SUCCESSFUL,
-         getRequestGroup()->getDownloadContext()->getBasePath().c_str());
+      A2_LOG_NOTICE
+        (fmt(MSG_VERIFICATION_SUCCESSFUL,
+             getRequestGroup()->getDownloadContext()->getBasePath().c_str()));
       std::vector<Command*>* commands = new std::vector<Command*>();
       auto_delete_container<std::vector<Command*> > commandsDel(commands);
       entry_->onDownloadFinished(*commands, getDownloadEngine());
       getDownloadEngine()->addCommand(*commands);
       commands->clear();
     } else {
-      getLogger()->error
-        (MSG_VERIFICATION_FAILED,
-         getRequestGroup()->getDownloadContext()->getBasePath().c_str());
+      A2_LOG_ERROR
+        (fmt(MSG_VERIFICATION_FAILED,
+             getRequestGroup()->getDownloadContext()->getBasePath().c_str()));
       std::vector<Command*>* commands = new std::vector<Command*>();
       auto_delete_container<std::vector<Command*> > commandsDel(commands);
       entry_->onDownloadIncomplete(*commands, getDownloadEngine());
@@ -98,12 +100,13 @@ bool CheckIntegrityCommand::executeInternal()
 bool CheckIntegrityCommand::handleException(Exception& e)
 {
   getDownloadEngine()->getCheckIntegrityMan()->dropPickedEntry();
-  getLogger()->error(MSG_FILE_VALIDATION_FAILURE, e,
-                     util::itos(getCuid()).c_str());
-  getLogger()->error
-    (MSG_DOWNLOAD_NOT_COMPLETE,
-     util::itos(getCuid()).c_str(),
-     getRequestGroup()->getDownloadContext()->getBasePath().c_str());
+  A2_LOG_ERROR_EX(fmt(MSG_FILE_VALIDATION_FAILURE,
+                   util::itos(getCuid()).c_str()),
+                  e);
+  A2_LOG_ERROR
+    (fmt(MSG_DOWNLOAD_NOT_COMPLETE,
+         util::itos(getCuid()).c_str(),
+         getRequestGroup()->getDownloadContext()->getBasePath().c_str()));
   return true;
 }
 
diff --git a/src/CheckIntegrityDispatcherCommand.cc b/src/CheckIntegrityDispatcherCommand.cc
index 9c76e662..8cef2de4 100644
--- a/src/CheckIntegrityDispatcherCommand.cc
+++ b/src/CheckIntegrityDispatcherCommand.cc
@@ -37,15 +37,17 @@
 #include "CheckIntegrityCommand.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 CheckIntegrityDispatcherCommand::CheckIntegrityDispatcherCommand
 (cuid_t cuid,
  const SharedHandle<CheckIntegrityMan>& fileAllocMan,
- DownloadEngine* e):SequentialDispatcherCommand<CheckIntegrityEntry>
-                    (cuid, fileAllocMan, e)
+ DownloadEngine* e)
+  : SequentialDispatcherCommand<CheckIntegrityEntry>(cuid, fileAllocMan, e)
 {
   setStatusRealtime();
 }
@@ -54,11 +56,9 @@ Command* CheckIntegrityDispatcherCommand::createCommand
 (const SharedHandle<CheckIntegrityEntry>& entry)
 {
   cuid_t newCUID = getDownloadEngine()->newCUID();
-  if(getLogger()->info()) {
-    getLogger()->info("CUID#%s - Dispatching CheckIntegrityCommand CUID#%s.",
-                      util::itos(getCuid()).c_str(),
-                      util::itos(newCUID).c_str());
-  }
+  A2_LOG_INFO(fmt("CUID#%s - Dispatching CheckIntegrityCommand CUID#%s.",
+                  util::itos(getCuid()).c_str(),
+                  util::itos(newCUID).c_str()));
   return new CheckIntegrityCommand
     (newCUID, entry->getRequestGroup(), getDownloadEngine(), entry);
 }
diff --git a/src/Command.cc b/src/Command.cc
index 8758f334..82db3178 100644
--- a/src/Command.cc
+++ b/src/Command.cc
@@ -34,17 +34,17 @@
 /* copyright --> */
 #include "Command.h"
 #include "LogFactory.h"
-#include "Logger.h"
 
 namespace aria2 {
 
-Command::Command(cuid_t cuid):status_(STATUS_INACTIVE),
-                              cuid_(cuid),
-                              logger_(LogFactory::getInstance()),
-                              readEvent_(false),
-                              writeEvent_(false),
-                              errorEvent_(false),
-                              hupEvent_(false) {}
+Command::Command(cuid_t cuid)
+  : status_(STATUS_INACTIVE),
+    cuid_(cuid),
+    readEvent_(false),
+    writeEvent_(false),
+    errorEvent_(false),
+    hupEvent_(false)
+{}
 
 void Command::transitStatus()
 {
diff --git a/src/Command.h b/src/Command.h
index 8b724045..a164661d 100644
--- a/src/Command.h
+++ b/src/Command.h
@@ -39,8 +39,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 typedef int64_t cuid_t;
 
 class Command {
@@ -56,18 +54,12 @@ private:
   STATUS status_;
 
   cuid_t cuid_;
-  Logger* logger_;
 
   bool readEvent_;
   bool writeEvent_;
   bool errorEvent_;
   bool hupEvent_;
 protected:
-  Logger* getLogger() const
-  {
-    return logger_;
-  }
-
   bool readEventEnabled() const
   {
     return readEvent_;
diff --git a/src/CookieStorage.cc b/src/CookieStorage.cc
index 6ebb99cd..d555c72c 100644
--- a/src/CookieStorage.cc
+++ b/src/CookieStorage.cc
@@ -43,6 +43,7 @@
 #include "Logger.h"
 #include "DlAbortEx.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "NsCookieParser.h"
 #include "File.h"
 #include "a2functional.h"
@@ -139,7 +140,7 @@ bool CookieStorage::DomainEntry::operator<(const DomainEntry& de) const
   return key_ < de.key_;
 }
 
-CookieStorage::CookieStorage():logger_(LogFactory::getInstance()) {}
+CookieStorage::CookieStorage() {}
 
 CookieStorage::~CookieStorage() {}
 
@@ -326,13 +327,13 @@ bool CookieStorage::load(const std::string& filename, time_t now)
   char header[16]; // "SQLite format 3" plus \0
   std::ifstream s(filename.c_str(), std::ios::binary);
   if(!s) {
-    logger_->error("Failed to open cookie file %s", filename.c_str());
+    A2_LOG_ERROR(fmt("Failed to open cookie file %s", filename.c_str()));
     return false;
   }
   s.get(header, sizeof(header));
   if(!s) {
-    logger_->error("Failed to read header of cookie file %s",
-                   filename.c_str());
+    A2_LOG_ERROR(fmt("Failed to read header of cookie file %s",
+                     filename.c_str()));
     return false;
   }
   try {
@@ -342,11 +343,9 @@ bool CookieStorage::load(const std::string& filename, time_t now)
       try {
         Sqlite3MozCookieParser(filename).parse(cookies);
       } catch(RecoverableException& e) {
-        if(logger_->info()) {
-          logger_->info(EX_EXCEPTION_CAUGHT, e);
-          logger_->info("This does not look like Firefox3 cookie file."
-                        " Retrying, assuming it is Chromium cookie file.");
-        }
+        A2_LOG_INFO_EX(EX_EXCEPTION_CAUGHT, e);
+        A2_LOG_INFO("This does not look like Firefox3 cookie file."
+                    " Retrying, assuming it is Chromium cookie file.");
         // Try chrome cookie format
         Sqlite3ChromiumCookieParser(filename).parse(cookies);
       }
@@ -362,7 +361,7 @@ bool CookieStorage::load(const std::string& filename, time_t now)
     }
     return true;
   } catch(RecoverableException& e) {
-    logger_->error("Failed to load cookies from %s", filename.c_str());
+    A2_LOG_ERROR(fmt("Failed to load cookies from %s", filename.c_str()));
     return false;
   }
 }
@@ -373,7 +372,7 @@ bool CookieStorage::saveNsFormat(const std::string& filename)
   {
     std::ofstream o(tempfilename.c_str(), std::ios::binary);
     if(!o) {
-      logger_->error("Cannot create cookie file %s", filename.c_str());
+      A2_LOG_ERROR(fmt("Cannot create cookie file %s", filename.c_str()));
       return false;
     }
     for(std::deque<DomainEntry>::const_iterator i = domains_.begin(),
@@ -382,15 +381,16 @@ bool CookieStorage::saveNsFormat(const std::string& filename)
     }
     o.flush();
     if(!o) {
-      logger_->error("Failed to save cookies to %s", filename.c_str());
+      A2_LOG_ERROR(fmt("Failed to save cookies to %s", filename.c_str()));
       return false;
     }  
   }
   if(File(tempfilename).renameTo(filename)) {
     return true;
   } else {
-    logger_->error("Could not rename file %s as %s",
-                   tempfilename.c_str(), filename.c_str());
+    A2_LOG_ERROR(fmt("Could not rename file %s as %s",
+                     tempfilename.c_str(),
+                     filename.c_str()));
     return false;
   }
 }
diff --git a/src/CookieStorage.h b/src/CookieStorage.h
index d56be1c0..8e9aa3e6 100644
--- a/src/CookieStorage.h
+++ b/src/CookieStorage.h
@@ -47,8 +47,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class CookieStorage {
 public:
 
@@ -122,8 +120,6 @@ public:
 private:
   std::deque<DomainEntry> domains_;
 
-  Logger* logger_;
-
   template<typename InputIterator>
   void storeCookies(InputIterator first, InputIterator last, time_t now)
   {
diff --git a/src/DHTAbstractNodeLookupTask.h b/src/DHTAbstractNodeLookupTask.h
index 0922d8fa..f5435ad5 100644
--- a/src/DHTAbstractNodeLookupTask.h
+++ b/src/DHTAbstractNodeLookupTask.h
@@ -55,6 +55,7 @@
 #include "util.h"
 #include "DHTIDCloser.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -102,19 +103,15 @@ private:
       sendMessage();
     }
     if(inFlightMessage_ == 0) {
-      if(getLogger()->debug()) {
-        getLogger()->debug("Finished node_lookup for node ID %s",
-                           util::toHex(targetID_, DHT_ID_LENGTH).c_str());
-      }
+      A2_LOG_DEBUG(fmt("Finished node_lookup for node ID %s",
+                       util::toHex(targetID_, DHT_ID_LENGTH).c_str()));
       onFinish();
       updateBucket();
       setFinished(true);
     } else {
-      if(getLogger()->debug()) {
-        getLogger()->debug("%lu in flight message for node ID %s",
-                           static_cast<unsigned long>(inFlightMessage_),
-                           util::toHex(targetID_, DHT_ID_LENGTH).c_str());
-      }
+      A2_LOG_DEBUG(fmt("%lu in flight message for node ID %s",
+                       static_cast<unsigned long>(inFlightMessage_),
+                       util::toHex(targetID_, DHT_ID_LENGTH).c_str()));
     }
   }
 
@@ -167,9 +164,7 @@ public:
       inFlightMessage_ = 0;
       sendMessage();
       if(inFlightMessage_ == 0) {
-        if(getLogger()->debug()) {
-          getLogger()->debug("No message was sent in this lookup stage. Finished.");
-        }
+        A2_LOG_DEBUG("No message was sent in this lookup stage. Finished.");
         setFinished(true);
       }
     }
@@ -191,27 +186,21 @@ public:
                 DHT_ID_LENGTH) != 0) {
         entries_.push_front(*i);
         ++count;
-        if(getLogger()->debug()) {
-          getLogger()->debug("Received nodes: id=%s, ip=%s",
-                             util::toHex((*i)->node->getID(),
-                                         DHT_ID_LENGTH).c_str(),
-                             (*i)->node->getIPAddress().c_str());
-        }
+        A2_LOG_DEBUG(fmt("Received nodes: id=%s, ip=%s",
+                         util::toHex((*i)->node->getID(),
+                                     DHT_ID_LENGTH).c_str(),
+                         (*i)->node->getIPAddress().c_str()));
       }
     }
-    if(getLogger()->debug()) {
-      getLogger()->debug("%lu node lookup entries added.",
-                         static_cast<unsigned long>(count));
-    }
+    A2_LOG_DEBUG(fmt("%lu node lookup entries added.",
+                     static_cast<unsigned long>(count)));
     std::stable_sort(entries_.begin(), entries_.end(), DHTIDCloser(targetID_));
     entries_.erase
       (std::unique(entries_.begin(), entries_.end(),
                    DerefEqualTo<SharedHandle<DHTNodeLookupEntry> >()),
        entries_.end());
-    if(getLogger()->debug()) {
-      getLogger()->debug("%lu node lookup entries are unique.",
-                         static_cast<unsigned long>(entries_.size()));
-    }
+    A2_LOG_DEBUG(fmt("%lu node lookup entries are unique.",
+                     static_cast<unsigned long>(entries_.size())));
     if(entries_.size() > DHTBucket::K) {
       entries_.erase(entries_.begin()+DHTBucket::K, entries_.end());
     }
@@ -220,10 +209,8 @@ public:
 
   void onTimeout(const SharedHandle<DHTNode>& node)
   {
-    if(getLogger()->debug()) {
-      getLogger()->debug("node lookup message timeout for node ID=%s",
-                         util::toHex(node->getID(), DHT_ID_LENGTH).c_str());
-    }
+    A2_LOG_DEBUG(fmt("node lookup message timeout for node ID=%s",
+                     util::toHex(node->getID(), DHT_ID_LENGTH).c_str()));
     --inFlightMessage_;
     for(std::deque<SharedHandle<DHTNodeLookupEntry> >::iterator i =
           entries_.begin(), eoi = entries_.end(); i != eoi; ++i) {
diff --git a/src/DHTAbstractTask.cc b/src/DHTAbstractTask.cc
index 076c0596..962f37a4 100644
--- a/src/DHTAbstractTask.cc
+++ b/src/DHTAbstractTask.cc
@@ -41,14 +41,12 @@
 #include "DHTMessageCallback.h"
 #include "DHTBucket.h"
 #include "DHTTaskQueue.h"
-#include "LogFactory.h"
 #include "util.h"
 
 namespace aria2 {
 
 DHTAbstractTask::DHTAbstractTask():
   finished_(false),
-  logger_(LogFactory::getInstance()),
   routingTable_(0),
   dispatcher_(0),
   factory_(0),
diff --git a/src/DHTAbstractTask.h b/src/DHTAbstractTask.h
index f5ce4c5a..e6b24049 100644
--- a/src/DHTAbstractTask.h
+++ b/src/DHTAbstractTask.h
@@ -48,14 +48,10 @@ class DHTMessageFactory;
 class DHTMessage;
 class DHTTaskQueue;
 
-class Logger;
-
 class DHTAbstractTask:public DHTTask {
 private:
   bool finished_;
   
-  Logger* logger_;
-  
   SharedHandle<DHTNode> localNode_;
 
   DHTRoutingTable* routingTable_;
@@ -70,11 +66,6 @@ protected:
   {
     finished_ = f;
   }
-
-  Logger* getLogger() const
-  {
-    return logger_;
-  }
 public:
   DHTAbstractTask();
 
diff --git a/src/DHTAutoSaveCommand.cc b/src/DHTAutoSaveCommand.cc
index f9b06118..308e72e2 100644
--- a/src/DHTAutoSaveCommand.cc
+++ b/src/DHTAutoSaveCommand.cc
@@ -49,17 +49,20 @@
 #include "Option.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "a2functional.h"
 #include "FileEntry.h"
 #include "DlAbortEx.h"
 #include "StringFormat.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 DHTAutoSaveCommand::DHTAutoSaveCommand
-(cuid_t cuid, DownloadEngine* e, int family, time_t interval):
-  TimeBasedCommand(cuid, e, interval),
-  family_(family) {}
+(cuid_t cuid, DownloadEngine* e, int family, time_t interval)
+ : TimeBasedCommand(cuid, e, interval),
+   family_(family)
+{}
 
 DHTAutoSaveCommand::~DHTAutoSaveCommand() {}
 
@@ -82,7 +85,7 @@ void DHTAutoSaveCommand::save()
   std::string dhtFile =
     getDownloadEngine()->getOption()->
     get(family_ == AF_INET? PREF_DHT_FILE_PATH : PREF_DHT_FILE_PATH6);
-  getLogger()->info("Saving DHT routing table to %s.", dhtFile.c_str());
+  A2_LOG_INFO(fmt("Saving DHT routing table to %s.", dhtFile.c_str()));
 
   File tempFile(dhtFile+"__temp");
   // Removing tempFile is unnecessary because the file is truncated on
@@ -118,12 +121,13 @@ void DHTAutoSaveCommand::save()
       serializer.serialize(o);
     }
     if(!tempFile.renameTo(dhtFile)) {
-      getLogger()->error("Cannot move file from %s to %s.",
-                         tempFile.getPath().c_str(), dhtFile.c_str());
+      A2_LOG_ERROR(fmt("Cannot move file from %s to %s.",
+                       tempFile.getPath().c_str(), dhtFile.c_str()));
     }
   } catch(RecoverableException& e) {
-    getLogger()->error("Exception caught while saving DHT routing table to %s",
-                       e, dhtFile.c_str());
+    A2_LOG_ERROR_EX(fmt("Exception caught while saving DHT routing table to %s",
+                        dhtFile.c_str()),
+                    e);
   }
 }
 
diff --git a/src/DHTBucket.cc b/src/DHTBucket.cc
index 258b7ada..ee5d0cae 100644
--- a/src/DHTBucket.cc
+++ b/src/DHTBucket.cc
@@ -47,26 +47,26 @@
 #include "bittorrent_helper.h"
 #include "bitfield.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTBucket::DHTBucket(size_t prefixLength,
-                     const unsigned char* max, const unsigned char* min,
-                     const SharedHandle<DHTNode>& localNode):
-  prefixLength_(prefixLength),
-  localNode_(localNode),
-  lastUpdated_(global::wallclock),
-  logger_(LogFactory::getInstance())
+DHTBucket::DHTBucket
+(size_t prefixLength,
+ const unsigned char* max, const unsigned char* min,
+ const SharedHandle<DHTNode>& localNode)
+  : prefixLength_(prefixLength),
+    localNode_(localNode),
+    lastUpdated_(global::wallclock)
 {
   memcpy(max_, max, DHT_ID_LENGTH);
   memcpy(min_, min, DHT_ID_LENGTH);
 }
 
-DHTBucket::DHTBucket(const SharedHandle<DHTNode>& localNode):
-  prefixLength_(0),
-  localNode_(localNode),
-  lastUpdated_(global::wallclock),
-  logger_(LogFactory::getInstance())
+DHTBucket::DHTBucket(const SharedHandle<DHTNode>& localNode)
+  : prefixLength_(0),
+    localNode_(localNode),
+    lastUpdated_(global::wallclock)
 {
   memset(max_, 0xffu, DHT_ID_LENGTH);
   memset(min_, 0, DHT_ID_LENGTH);
@@ -206,16 +206,14 @@ SharedHandle<DHTBucket> DHTBucket::split()
   }
   nodes_ = lNodes;
   // TODO create toString() and use it.
-  if(logger_->debug()) {
-    logger_->debug("New bucket. prefixLength=%u, Range:%s-%s",
+  A2_LOG_DEBUG(fmt("New bucket. prefixLength=%u, Range:%s-%s",
                    static_cast<unsigned int>(rBucket->getPrefixLength()),
                    util::toHex(rBucket->getMinID(), DHT_ID_LENGTH).c_str(),
-                   util::toHex(rBucket->getMaxID(), DHT_ID_LENGTH).c_str());
-    logger_->debug("Existing bucket. prefixLength=%u, Range:%s-%s",
+                   util::toHex(rBucket->getMaxID(), DHT_ID_LENGTH).c_str()));
+  A2_LOG_DEBUG(fmt("Existing bucket. prefixLength=%u, Range:%s-%s",
                    static_cast<unsigned int>(prefixLength_),
                    util::toHex(getMinID(), DHT_ID_LENGTH).c_str(),
-                   util::toHex(getMaxID(), DHT_ID_LENGTH).c_str());
-  }
+                   util::toHex(getMaxID(), DHT_ID_LENGTH).c_str()));
   return rBucket;
 }
 
diff --git a/src/DHTBucket.h b/src/DHTBucket.h
index 9d71a251..0f4cbceb 100644
--- a/src/DHTBucket.h
+++ b/src/DHTBucket.h
@@ -48,7 +48,6 @@
 namespace aria2 {
 
 class DHTNode;
-class Logger;
 
 class DHTBucket {
 private:
@@ -70,8 +69,6 @@ private:
 
   Timer lastUpdated_;
 
-  Logger* logger_;
-
   bool isInRange(const unsigned char* nodeID,
                  const unsigned char* max, const unsigned char* min) const;
 public:
diff --git a/src/DHTBucketRefreshTask.cc b/src/DHTBucketRefreshTask.cc
index e95c3dc2..7b76138c 100644
--- a/src/DHTBucketRefreshTask.cc
+++ b/src/DHTBucketRefreshTask.cc
@@ -41,7 +41,9 @@
 #include "DHTNodeLookupEntry.h"
 #include "util.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "DHTMessageCallback.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -67,8 +69,8 @@ void DHTBucketRefreshTask::startup()
       task->setTaskQueue(getTaskQueue());
       task->setLocalNode(getLocalNode());
 
-      getLogger()->info("Dispating bucket refresh. targetID=%s",
-                        util::toHex(targetID, DHT_ID_LENGTH).c_str());
+      A2_LOG_INFO(fmt("Dispating bucket refresh. targetID=%s",
+                      util::toHex(targetID, DHT_ID_LENGTH).c_str()));
       getTaskQueue()->addPeriodicTask1(task);
     }
   }
diff --git a/src/DHTConnectionImpl.cc b/src/DHTConnectionImpl.cc
index 9a2e44f6..86f04f72 100644
--- a/src/DHTConnectionImpl.cc
+++ b/src/DHTConnectionImpl.cc
@@ -43,13 +43,14 @@
 #include "util.h"
 #include "Socket.h"
 #include "SimpleRandomizer.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTConnectionImpl::DHTConnectionImpl(int family):
-  socket_(new SocketCore(SOCK_DGRAM)),
-  family_(family),
-  logger_(LogFactory::getInstance()) {}
+DHTConnectionImpl::DHTConnectionImpl(int family)
+  : socket_(new SocketCore(SOCK_DGRAM)),
+    family_(family)
+{}
 
 DHTConnectionImpl::~DHTConnectionImpl() {}
 
@@ -86,10 +87,11 @@ bool DHTConnectionImpl::bind(uint16_t& port, const std::string& addr)
     std::pair<std::string, uint16_t> svaddr;
     socket_->getAddrInfo(svaddr);
     port = svaddr.second;
-    logger_->notice("IPv%d DHT: listening to port %d", ipv, port);
+    A2_LOG_NOTICE(fmt("IPv%d DHT: listening to port %d", ipv, port));
     return true;
   } catch(RecoverableException& e) {
-    logger_->error("Failed to bind for IPv%d DHT. port=%u", e, ipv, port);
+    A2_LOG_ERROR_EX(fmt("Failed to bind for IPv%d DHT. port=%u", ipv, port),
+                    e);
   }
   return false;
 }
diff --git a/src/DHTConnectionImpl.h b/src/DHTConnectionImpl.h
index a7c0b1f6..c05d184c 100644
--- a/src/DHTConnectionImpl.h
+++ b/src/DHTConnectionImpl.h
@@ -42,15 +42,12 @@
 namespace aria2 {
 
 class SocketCore;
-class Logger;
 
 class DHTConnectionImpl:public DHTConnection {
 private:
   SharedHandle<SocketCore> socket_;
 
   int family_;
-
-  Logger* logger_;
 public:
   DHTConnectionImpl(int family);
 
diff --git a/src/DHTEntryPointNameResolveCommand.cc b/src/DHTEntryPointNameResolveCommand.cc
index 9f4c1a5f..20f506a7 100644
--- a/src/DHTEntryPointNameResolveCommand.cc
+++ b/src/DHTEntryPointNameResolveCommand.cc
@@ -47,7 +47,9 @@
 #include "DHTTask.h"
 #include "RequestGroupMan.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #ifdef ENABLE_ASYNC_DNS
 #include "AsyncNameResolver.h"
 #endif // ENABLE_ASYNC_DNS
@@ -108,7 +110,7 @@ bool DHTEntryPointNameResolveCommand::execute()
             return false;
           }
         } catch(RecoverableException& e) {
-          getLogger()->error(EX_EXCEPTION_CAUGHT, e);
+          A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
         }
         resolver_->reset();
         entryPoints_.pop_front();
@@ -129,7 +131,7 @@ bool DHTEntryPointNameResolveCommand::execute()
             resolvedEntryPoints_.push_back(p);
             addPingTask(p);
           } catch(RecoverableException& e) {
-            getLogger()->error(EX_EXCEPTION_CAUGHT, e);
+            A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
           }
           entryPoints_.pop_front();
         }
@@ -140,7 +142,7 @@ bool DHTEntryPointNameResolveCommand::execute()
       taskQueue_->addPeriodicTask1(taskFactory_->createBucketRefreshTask());
     }
   } catch(RecoverableException& e) {
-    getLogger()->error(EX_EXCEPTION_CAUGHT, e);
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
   }
   return true;
 }
@@ -163,20 +165,17 @@ bool DHTEntryPointNameResolveCommand::resolveHostname
 {
   switch(resolver->getStatus()) {
   case AsyncNameResolver::STATUS_READY:
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_RESOLVING_HOSTNAME,
-                        util::itos(getCuid()).c_str(), hostname.c_str());
-    }
+      A2_LOG_INFO(fmt(MSG_RESOLVING_HOSTNAME,
+                      util::itos(getCuid()).c_str(),
+                      hostname.c_str()));
     resolver->resolve(hostname);
     setNameResolverCheck(resolver);
     return false;
   case AsyncNameResolver::STATUS_SUCCESS:
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_NAME_RESOLUTION_COMPLETE,
-                        util::itos(getCuid()).c_str(),
-                        resolver->getHostname().c_str(),
-                        resolver->getResolvedAddresses().front().c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_NAME_RESOLUTION_COMPLETE,
+                    util::itos(getCuid()).c_str(),
+                    resolver->getHostname().c_str(),
+                    resolver->getResolvedAddresses().front().c_str()));
     return true;
     break;
   case AsyncNameResolver::STATUS_ERROR:
diff --git a/src/DHTGetPeersCommand.cc b/src/DHTGetPeersCommand.cc
index f48a6149..96e2a3e5 100644
--- a/src/DHTGetPeersCommand.cc
+++ b/src/DHTGetPeersCommand.cc
@@ -44,20 +44,23 @@
 #include "PeerStorage.h"
 #include "Peer.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "bittorrent_helper.h"
 #include "DownloadContext.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTGetPeersCommand::DHTGetPeersCommand(cuid_t cuid,
-                                       RequestGroup* requestGroup,
-                                       DownloadEngine* e):
-  Command(cuid),
-  requestGroup_(requestGroup),
-  e_(e),
-  numRetry_(0),
-  lastGetPeerTime_(0)
+DHTGetPeersCommand::DHTGetPeersCommand
+(cuid_t cuid,
+ RequestGroup* requestGroup,
+ DownloadEngine* e)
+  : Command(cuid),
+    requestGroup_(requestGroup),
+    e_(e),
+    numRetry_(0),
+    lastGetPeerTime_(0)
 {
   requestGroup_->increaseNumCommand();
 }
@@ -79,11 +82,9 @@ bool DHTGetPeersCommand::execute()
       (btRuntime_->lessThanMinPeers() &&
        lastGetPeerTime_.difference(global::wallclock) >= GET_PEER_MIN_INTERVAL
        && !requestGroup_->downloadFinished()))) {
-    if(getLogger()->debug()) {
-      getLogger()->debug("Issuing PeerLookup for infoHash=%s",
-                         bittorrent::getInfoHashString
-                         (requestGroup_->getDownloadContext()).c_str());
-    }
+    A2_LOG_DEBUG(fmt("Issuing PeerLookup for infoHash=%s",
+                     bittorrent::getInfoHashString
+                     (requestGroup_->getDownloadContext()).c_str()));
     task_ = taskFactory_->createPeerLookupTask
       (requestGroup_->getDownloadContext(), btRuntime_, peerStorage_);
     taskQueue_->addPeriodicTask2(task_);
diff --git a/src/DHTInteractionCommand.cc b/src/DHTInteractionCommand.cc
index c67aab2f..101d6a22 100644
--- a/src/DHTInteractionCommand.cc
+++ b/src/DHTInteractionCommand.cc
@@ -43,14 +43,17 @@
 #include "message.h"
 #include "RequestGroupMan.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "DHTMessageCallback.h"
 #include "DHTNode.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTInteractionCommand::DHTInteractionCommand(cuid_t cuid, DownloadEngine* e):
-  Command(cuid),
-  e_(e) {}
+DHTInteractionCommand::DHTInteractionCommand(cuid_t cuid, DownloadEngine* e)
+  : Command(cuid),
+    e_(e)
+{}
 
 DHTInteractionCommand::~DHTInteractionCommand()
 {
@@ -86,7 +89,7 @@ bool DHTInteractionCommand::execute()
   try {
     dispatcher_->sendMessages();
   } catch(RecoverableException& e) {
-    getLogger()->error(EX_EXCEPTION_CAUGHT, e);
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
   }
   e_->addCommand(this);
   return false;
diff --git a/src/DHTMessageDispatcherImpl.cc b/src/DHTMessageDispatcherImpl.cc
index f786b5fb..cbfe7c64 100644
--- a/src/DHTMessageDispatcherImpl.cc
+++ b/src/DHTMessageDispatcherImpl.cc
@@ -42,15 +42,16 @@
 #include "Logger.h"
 #include "DHTConstants.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "DHTNode.h"
 
 namespace aria2 {
 
 DHTMessageDispatcherImpl::DHTMessageDispatcherImpl
-(const SharedHandle<DHTMessageTracker>& tracker):
-  tracker_(tracker),
-  timeout_(DHT_MESSAGE_TIMEOUT),
-  logger_(LogFactory::getInstance()) {}
+(const SharedHandle<DHTMessageTracker>& tracker)
+  : tracker_(tracker),
+    timeout_(DHT_MESSAGE_TIMEOUT)
+{}
 
 DHTMessageDispatcherImpl::~DHTMessageDispatcherImpl() {}
 
@@ -82,15 +83,14 @@ DHTMessageDispatcherImpl::sendMessage
       if(!entry->message->isReply()) {
         tracker_->addMessage(entry->message, entry->timeout, entry->callback);
       }
-      if(logger_->info()) {
-        logger_->info("Message sent: %s", entry->message->toString().c_str());
-      }
+      A2_LOG_INFO(fmt("Message sent: %s", entry->message->toString().c_str()));
     } else {
       return false;
     }
   } catch(RecoverableException& e) {
-    logger_->info("Failed to send message: %s",
-                  e, entry->message->toString().c_str());
+    A2_LOG_INFO_EX(fmt("Failed to send message: %s",
+                       entry->message->toString().c_str()),
+                   e);
     // Add message to DHTMessageTracker with timeout 0 to treat it as
     // time out. Without this, we have untracked message and some of
     // DHTTask(such as DHTAbstractNodeLookupTask) don't finish
@@ -114,10 +114,8 @@ void DHTMessageDispatcherImpl::sendMessages()
     }
   }
   messageQueue_.erase(messageQueue_.begin(), itr);
-  if(logger_->debug()) {
-    logger_->debug("%lu dht messages remaining in the queue.",
-                   static_cast<unsigned long>(messageQueue_.size()));
-  }
+  A2_LOG_DEBUG(fmt("%lu dht messages remaining in the queue.",
+                   static_cast<unsigned long>(messageQueue_.size())));
 }
 
 size_t DHTMessageDispatcherImpl::countMessageInQueue() const
diff --git a/src/DHTMessageDispatcherImpl.h b/src/DHTMessageDispatcherImpl.h
index 953ce7e6..d0f2090e 100644
--- a/src/DHTMessageDispatcherImpl.h
+++ b/src/DHTMessageDispatcherImpl.h
@@ -42,7 +42,6 @@ namespace aria2 {
 
 class DHTMessageTracker;
 struct DHTMessageEntry;
-class Logger;
 
 class DHTMessageDispatcherImpl:public DHTMessageDispatcher {
 private:
@@ -52,8 +51,6 @@ private:
 
   time_t timeout_;
 
-  Logger* logger_;
-
   bool sendMessage(const SharedHandle<DHTMessageEntry>& msg);
 public:
   DHTMessageDispatcherImpl(const SharedHandle<DHTMessageTracker>& tracker);
diff --git a/src/DHTMessageFactoryImpl.cc b/src/DHTMessageFactoryImpl.cc
index b3294800..681d3238 100644
--- a/src/DHTMessageFactoryImpl.cc
+++ b/src/DHTMessageFactoryImpl.cc
@@ -61,17 +61,18 @@
 #include "Peer.h"
 #include "Logger.h"
 #include "StringFormat.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTMessageFactoryImpl::DHTMessageFactoryImpl(int family):
-  family_(family),
-  connection_(0),
-  dispatcher_(0),
-  routingTable_(0),
-  peerAnnounceStorage_(0),
-  tokenTracker_(0),
-  logger_(LogFactory::getInstance()) {}
+DHTMessageFactoryImpl::DHTMessageFactoryImpl(int family)
+  : family_(family),
+    connection_(0),
+    dispatcher_(0),
+    routingTable_(0),
+    peerAnnounceStorage_(0),
+    tokenTracker_(0)
+{}
 
 DHTMessageFactoryImpl::~DHTMessageFactoryImpl() {}
 
@@ -256,15 +257,11 @@ DHTMessageFactoryImpl::createResponseMessage
     // for now, just report error message arrived and throw exception.
     const List* e = getList(dict, DHTUnknownMessage::E);
     if(e->size() == 2) {
-      if(logger_->info()) {
-        logger_->info("Received Error DHT message. code=%s, msg=%s",
+      A2_LOG_INFO(fmt("Received Error DHT message. code=%s, msg=%s",
                       util::itos(getInteger(e, 0)->i()).c_str(),
-                      util::percentEncode(getString(e, 1)->s()).c_str());
-      }
+                      util::percentEncode(getString(e, 1)->s()).c_str()));
     } else {
-      if(logger_->debug()) {
-        logger_->debug("e doesn't have 2 elements.");
-      }
+      A2_LOG_DEBUG("e doesn't have 2 elements.");
     }
     throw DL_ABORT_EX("Received Error DHT message.");
   } else if(y->s() != DHTResponseMessage::R) {
diff --git a/src/DHTMessageFactoryImpl.h b/src/DHTMessageFactoryImpl.h
index 7bc41491..b4ddce27 100644
--- a/src/DHTMessageFactoryImpl.h
+++ b/src/DHTMessageFactoryImpl.h
@@ -45,7 +45,6 @@ class DHTMessageDispatcher;
 class DHTRoutingTable;
 class DHTPeerAnnounceStorage;
 class DHTTokenTracker;
-class Logger;
 class DHTMessage;
 class DHTAbstractMessage;
 
@@ -64,8 +63,6 @@ private:
   DHTPeerAnnounceStorage* peerAnnounceStorage_;
 
   DHTTokenTracker* tokenTracker_;
-
-  Logger* logger_;
   
   // search node in routingTable. If it is not found, create new one.
   SharedHandle<DHTNode> getRemoteNode
diff --git a/src/DHTMessageReceiver.cc b/src/DHTMessageReceiver.cc
index c6d4158d..35f3acc0 100644
--- a/src/DHTMessageReceiver.cc
+++ b/src/DHTMessageReceiver.cc
@@ -52,12 +52,13 @@
 #include "Logger.h"
 #include "util.h"
 #include "bencode2.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTMessageReceiver::DHTMessageReceiver(const SharedHandle<DHTMessageTracker>& tracker):
-  tracker_(tracker),
-  logger_(LogFactory::getInstance())
+DHTMessageReceiver::DHTMessageReceiver
+(const SharedHandle<DHTMessageTracker>& tracker)
+  : tracker_(tracker)
 {}
 
 DHTMessageReceiver::~DHTMessageReceiver() {}
@@ -84,13 +85,14 @@ SharedHandle<DHTMessage> DHTMessageReceiver::receiveMessage()
           isReply = true;
         }
       } else {
-        logger_->info("Malformed DHT message. Missing 'y' key. From:%s:%u",
-                      remoteAddr.c_str(), remotePort);
+        A2_LOG_INFO(fmt("Malformed DHT message. Missing 'y' key. From:%s:%u",
+                        remoteAddr.c_str(), remotePort));
         return handleUnknownMessage(data, sizeof(data), remoteAddr, remotePort);
       }
     } else {
-      logger_->info("Malformed DHT message. This is not a bencoded directory."
-                    " From:%s:%u", remoteAddr.c_str(), remotePort);
+      A2_LOG_INFO(fmt("Malformed DHT message. This is not a bencoded directory."
+                      " From:%s:%u",
+                      remoteAddr.c_str(), remotePort));
       return handleUnknownMessage(data, sizeof(data), remoteAddr, remotePort);
     }
     if(isReply) {
@@ -111,14 +113,14 @@ SharedHandle<DHTMessage> DHTMessageReceiver::receiveMessage()
         factory_->createQueryMessage(dict, remoteAddr, remotePort);
       if(*message->getLocalNode() == *message->getRemoteNode()) {
         // drop message from localnode
-        logger_->info("Received DHT message from localnode.");
+        A2_LOG_INFO("Received DHT message from localnode.");
         return handleUnknownMessage(data, sizeof(data), remoteAddr, remotePort);
       }
       onMessageReceived(message);
       return message;
     }
   } catch(RecoverableException& e) {
-    logger_->info("Exception thrown while receiving DHT message.", e);
+    A2_LOG_INFO_EX("Exception thrown while receiving DHT message.", e);
     return handleUnknownMessage(data, sizeof(data), remoteAddr, remotePort);
   }
 }
@@ -126,9 +128,7 @@ SharedHandle<DHTMessage> DHTMessageReceiver::receiveMessage()
 void DHTMessageReceiver::onMessageReceived
 (const SharedHandle<DHTMessage>& message)
 {
-  if(logger_->info()) {
-    logger_->info("Message received: %s", message->toString().c_str());
-  }
+  A2_LOG_INFO(fmt("Message received: %s", message->toString().c_str()));
   message->validate();
   message->doReceivedAction();
   message->getRemoteNode()->markGood();
@@ -149,9 +149,7 @@ DHTMessageReceiver::handleUnknownMessage(const unsigned char* data,
 {
   SharedHandle<DHTMessage> m =
     factory_->createUnknownMessage(data, length, remoteAddr, remotePort);
-  if(logger_->info()) {
-    logger_->info("Message received: %s", m->toString().c_str());
-  }
+  A2_LOG_INFO(fmt("Message received: %s", m->toString().c_str()));
   return m;
 }
 
diff --git a/src/DHTMessageReceiver.h b/src/DHTMessageReceiver.h
index 33935cf1..7d7fac2f 100644
--- a/src/DHTMessageReceiver.h
+++ b/src/DHTMessageReceiver.h
@@ -46,8 +46,6 @@ class DHTConnection;
 class DHTMessageFactory;
 class DHTRoutingTable;
 
-class Logger;
-
 class DHTMessageReceiver {
 private:
   SharedHandle<DHTMessageTracker> tracker_;
@@ -58,8 +56,6 @@ private:
 
   SharedHandle<DHTRoutingTable> routingTable_;
 
-  Logger* logger_;
-
   SharedHandle<DHTMessage>
   handleUnknownMessage(const unsigned char* data, size_t length,
                        const std::string& remoteAddr, uint16_t remotePort);
diff --git a/src/DHTMessageTracker.cc b/src/DHTMessageTracker.cc
index 88ec2db4..5dc7a6b6 100644
--- a/src/DHTMessageTracker.cc
+++ b/src/DHTMessageTracker.cc
@@ -48,11 +48,11 @@
 #include "DlAbortEx.h"
 #include "DHTConstants.h"
 #include "StringFormat.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTMessageTracker::DHTMessageTracker():
-  logger_(LogFactory::getInstance()) {}
+DHTMessageTracker::DHTMessageTracker() {}
 
 DHTMessageTracker::~DHTMessageTracker() {}
 
@@ -71,18 +71,15 @@ DHTMessageTracker::messageArrived
     throw DL_ABORT_EX(StringFormat("Malformed DHT message. From:%s:%u",
                                    ipaddr.c_str(), port).str());
   }
-  if(logger_->debug()) {
-    logger_->debug("Searching tracker entry for TransactionID=%s, Remote=%s:%u",
-                   util::toHex(tid->s()).c_str(), ipaddr.c_str(), port);
-  }
+  A2_LOG_DEBUG(fmt("Searching tracker entry for TransactionID=%s, Remote=%s:%u",
+                   util::toHex(tid->s()).c_str(),
+                   ipaddr.c_str(), port));
   for(std::deque<SharedHandle<DHTMessageTrackerEntry> >::iterator i =
         entries_.begin(), eoi = entries_.end(); i != eoi; ++i) {
     if((*i)->match(tid->s(), ipaddr, port)) {
       SharedHandle<DHTMessageTrackerEntry> entry = *i;
       entries_.erase(i);
-      if(logger_->debug()) {
-        logger_->debug("Tracker entry found.");
-      }
+      A2_LOG_DEBUG("Tracker entry found.");
       SharedHandle<DHTNode> targetNode = entry->getTargetNode();
       try {
         SharedHandle<DHTResponseMessage> message =
@@ -91,9 +88,7 @@ DHTMessageTracker::messageArrived
                                           targetNode->getPort());
 
         int64_t rtt = entry->getElapsedMillis();
-        if(logger_->debug()) {
-          logger_->debug("RTT is %s", util::itos(rtt).c_str());
-        }
+        A2_LOG_DEBUG(fmt("RTT is %s", util::itos(rtt).c_str()));
         message->getRemoteNode()->updateRTT(rtt);
         SharedHandle<DHTMessageCallback> callback = entry->getCallback();
         return std::make_pair(message, callback);
@@ -103,9 +98,7 @@ DHTMessageTracker::messageArrived
       }
     }
   }
-  if(logger_->debug()) {
-    logger_->debug("Tracker entry not found.");
-  }
+  A2_LOG_DEBUG("Tracker entry not found.");
   return std::pair<SharedHandle<DHTResponseMessage>,
                    SharedHandle<DHTMessageCallback> >();
 }
@@ -115,17 +108,13 @@ void DHTMessageTracker::handleTimeoutEntry
 {
   try {
     SharedHandle<DHTNode> node = entry->getTargetNode();
-    if(logger_->debug()) {
-      logger_->debug("Message timeout: To:%s:%u",
-                     node->getIPAddress().c_str(), node->getPort());
-    }
+    A2_LOG_DEBUG(fmt("Message timeout: To:%s:%u",
+                     node->getIPAddress().c_str(), node->getPort()));
     node->updateRTT(entry->getElapsedMillis());
     node->timeout();
     if(node->isBad()) {
-      if(logger_->debug()) {
-        logger_->debug("Marked bad: %s:%u",
-                       node->getIPAddress().c_str(), node->getPort());
-      }
+      A2_LOG_DEBUG(fmt("Marked bad: %s:%u",
+                       node->getIPAddress().c_str(), node->getPort()));
       routingTable_->dropNode(node);
     }
     SharedHandle<DHTMessageCallback> callback = entry->getCallback();
@@ -133,7 +122,7 @@ void DHTMessageTracker::handleTimeoutEntry
       callback->onTimeout(node);
     }
   } catch(RecoverableException& e) {
-    logger_->info("Exception thrown while handling timeouts.", e);
+    A2_LOG_INFO_EX("Exception thrown while handling timeouts.", e);
   }
 }
 
diff --git a/src/DHTMessageTracker.h b/src/DHTMessageTracker.h
index 4b674661..fae30052 100644
--- a/src/DHTMessageTracker.h
+++ b/src/DHTMessageTracker.h
@@ -52,7 +52,6 @@ class DHTMessageCallback;
 class DHTRoutingTable;
 class DHTMessageFactory;
 class DHTMessageTrackerEntry;
-class Logger;
 
 class DHTMessageTracker {
 private:
@@ -62,8 +61,6 @@ private:
 
   SharedHandle<DHTMessageFactory> factory_;
 
-  Logger* logger_;
-
   void handleTimeoutEntry(const SharedHandle<DHTMessageTrackerEntry>& entry);
 public:
   DHTMessageTracker();
diff --git a/src/DHTPeerAnnounceCommand.cc b/src/DHTPeerAnnounceCommand.cc
index 96fd3bda..9ab386cf 100644
--- a/src/DHTPeerAnnounceCommand.cc
+++ b/src/DHTPeerAnnounceCommand.cc
@@ -39,12 +39,14 @@
 #include "RecoverableException.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 
 namespace aria2 {
 
 DHTPeerAnnounceCommand::DHTPeerAnnounceCommand
-(cuid_t cuid, DownloadEngine* e, time_t interval):
-  TimeBasedCommand(cuid, e, interval) {}
+(cuid_t cuid, DownloadEngine* e, time_t interval)
+  : TimeBasedCommand(cuid, e, interval)
+{}
 
 DHTPeerAnnounceCommand::~DHTPeerAnnounceCommand() {}
 
@@ -61,7 +63,7 @@ void DHTPeerAnnounceCommand::process()
   try {
     peerAnnounceStorage_->handleTimeout();
   } catch(RecoverableException& e) {
-    getLogger()->error(EX_EXCEPTION_CAUGHT, e);
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
   }
 }
 
diff --git a/src/DHTPeerAnnounceStorage.cc b/src/DHTPeerAnnounceStorage.cc
index c7bf2426..d5530c9a 100644
--- a/src/DHTPeerAnnounceStorage.cc
+++ b/src/DHTPeerAnnounceStorage.cc
@@ -48,11 +48,11 @@
 #include "util.h"
 #include "a2functional.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTPeerAnnounceStorage::DHTPeerAnnounceStorage():
-  logger_(LogFactory::getInstance()) {}
+DHTPeerAnnounceStorage::DHTPeerAnnounceStorage() {}
 
 DHTPeerAnnounceStorage::~DHTPeerAnnounceStorage() {}
 
@@ -89,11 +89,9 @@ void
 DHTPeerAnnounceStorage::addPeerAnnounce(const unsigned char* infoHash,
                                         const std::string& ipaddr, uint16_t port)
 {
-  if(logger_->debug()) {
-    logger_->debug("Adding %s:%u to peer announce list: infoHash=%s",
+  A2_LOG_DEBUG(fmt("Adding %s:%u to peer announce list: infoHash=%s",
                    ipaddr.c_str(), port,
-                   util::toHex(infoHash, DHT_ID_LENGTH).c_str());
-  }
+                   util::toHex(infoHash, DHT_ID_LENGTH).c_str()));
   getPeerAnnounceEntry(infoHash)->addPeerAddrEntry(PeerAddrEntry(ipaddr, port));
 }
 
@@ -131,25 +129,19 @@ public:
 
 void DHTPeerAnnounceStorage::handleTimeout()
 {
-  if(logger_->debug()) {
-    logger_->debug("Now purge peer announces(%lu entries) which are timed out.",
-                   static_cast<unsigned long>(entries_.size()));
-  }
+  A2_LOG_DEBUG(fmt("Now purge peer announces(%lu entries) which are timed out.",
+                   static_cast<unsigned long>(entries_.size())));
   std::for_each(entries_.begin(), entries_.end(), RemoveStalePeerAddrEntry());
   entries_.erase(std::remove_if(entries_.begin(), entries_.end(),
                                 mem_fun_sh(&DHTPeerAnnounceEntry::empty)),
                  entries_.end());
-  if(logger_->debug()) {
-    logger_->debug("Currently %lu peer announce entries",
-                   static_cast<unsigned long>(entries_.size()));
-  }
+  A2_LOG_DEBUG(fmt("Currently %lu peer announce entries",
+                   static_cast<unsigned long>(entries_.size())));
 }
 
 void DHTPeerAnnounceStorage::announcePeer()
 {
-  if(logger_->debug()) {
-    logger_->debug("Now announcing peer.");
-  }
+  A2_LOG_DEBUG("Now announcing peer.");
   for(std::deque<SharedHandle<DHTPeerAnnounceEntry> >::iterator i =
         entries_.begin(), eoi = entries_.end(); i != eoi; ++i) {
     if((*i)->getLastUpdated().
@@ -158,10 +150,9 @@ void DHTPeerAnnounceStorage::announcePeer()
       SharedHandle<DHTTask> task =
         taskFactory_->createPeerAnnounceTask((*i)->getInfoHash());
       taskQueue_->addPeriodicTask2(task);
-      if(logger_->debug()) {
-        logger_->debug("Added 1 peer announce: infoHash=%s",
-                       util::toHex((*i)->getInfoHash(), DHT_ID_LENGTH).c_str());
-      }
+      A2_LOG_DEBUG
+        (fmt("Added 1 peer announce: infoHash=%s",
+             util::toHex((*i)->getInfoHash(), DHT_ID_LENGTH).c_str()));
     }
   }
 }
diff --git a/src/DHTPeerAnnounceStorage.h b/src/DHTPeerAnnounceStorage.h
index 7928b520..ceae63b1 100644
--- a/src/DHTPeerAnnounceStorage.h
+++ b/src/DHTPeerAnnounceStorage.h
@@ -48,7 +48,6 @@ class Peer;
 class DHTPeerAnnounceEntry;
 class DHTTaskQueue;
 class DHTTaskFactory;
-class Logger;
 
 class DHTPeerAnnounceStorage {
 private:
@@ -59,8 +58,6 @@ private:
   SharedHandle<DHTTaskQueue> taskQueue_;
 
   SharedHandle<DHTTaskFactory> taskFactory_;
-
-  Logger* logger_;
 public:
   DHTPeerAnnounceStorage();
 
diff --git a/src/DHTPeerLookupTask.cc b/src/DHTPeerLookupTask.cc
index 77d563e4..94c0de12 100644
--- a/src/DHTPeerLookupTask.cc
+++ b/src/DHTPeerLookupTask.cc
@@ -36,6 +36,7 @@
 #include "Peer.h"
 #include "DHTGetPeersReplyMessage.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "DHTMessageFactory.h"
 #include "DHTNode.h"
 #include "DHTNodeLookupEntry.h"
@@ -48,13 +49,15 @@
 #include "bittorrent_helper.h"
 #include "DHTPeerLookupTaskCallback.h"
 #include "DHTQueryMessage.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 DHTPeerLookupTask::DHTPeerLookupTask
-(const SharedHandle<DownloadContext>& downloadContext):
-  DHTAbstractNodeLookupTask<DHTGetPeersReplyMessage>
-  (bittorrent::getInfoHash(downloadContext)) {}
+(const SharedHandle<DownloadContext>& downloadContext)
+  : DHTAbstractNodeLookupTask<DHTGetPeersReplyMessage>
+    (bittorrent::getInfoHash(downloadContext))
+{}
 
 void
 DHTPeerLookupTask::getNodesFromMessage
@@ -75,8 +78,8 @@ void DHTPeerLookupTask::onReceivedInternal
   peerStorage_->addPeer(message->getValues());
   peers_.insert(peers_.end(),
                 message->getValues().begin(), message->getValues().end());
-  getLogger()->info("Received %lu peers.",
-                    static_cast<unsigned long>(message->getValues().size()));
+  A2_LOG_INFO(fmt("Received %lu peers.",
+                  static_cast<unsigned long>(message->getValues().size())));
 }
   
 SharedHandle<DHTMessage> DHTPeerLookupTask::createMessage
@@ -93,10 +96,8 @@ SharedHandle<DHTMessageCallback> DHTPeerLookupTask::createCallback()
 
 void DHTPeerLookupTask::onFinish()
 {
-  if(getLogger()->debug()) {
-    getLogger()->debug("Peer lookup for %s finished",
-                       util::toHex(getTargetID(), DHT_ID_LENGTH).c_str());
-  }
+  A2_LOG_DEBUG(fmt("Peer lookup for %s finished",
+                   util::toHex(getTargetID(), DHT_ID_LENGTH).c_str()));
   // send announce_peer message to K closest nodes
   size_t num = DHTBucket::K;
   for(std::deque<SharedHandle<DHTNodeLookupEntry> >::const_iterator i =
diff --git a/src/DHTReplaceNodeTask.cc b/src/DHTReplaceNodeTask.cc
index 66fa70c4..321f5821 100644
--- a/src/DHTReplaceNodeTask.cc
+++ b/src/DHTReplaceNodeTask.cc
@@ -39,17 +39,19 @@
 #include "DHTMessageFactory.h"
 #include "DHTMessageDispatcher.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "DHTPingReplyMessageCallback.h"
 #include "DHTQueryMessage.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTReplaceNodeTask::DHTReplaceNodeTask(const SharedHandle<DHTBucket>& bucket,
-                                       const SharedHandle<DHTNode>& newNode):
-  bucket_(bucket),
-  newNode_(newNode),
-  numRetry_(0),
-  timeout_(DHT_MESSAGE_TIMEOUT)
+DHTReplaceNodeTask::DHTReplaceNodeTask
+(const SharedHandle<DHTBucket>& bucket, const SharedHandle<DHTNode>& newNode)
+  : bucket_(bucket),
+    newNode_(newNode),
+    numRetry_(0),
+    timeout_(DHT_MESSAGE_TIMEOUT)
 {}
 
 DHTReplaceNodeTask::~DHTReplaceNodeTask() {}
@@ -75,8 +77,8 @@ void DHTReplaceNodeTask::sendMessage()
 
 void DHTReplaceNodeTask::onReceived(const DHTPingReplyMessage* message)
 {
-  getLogger()->info("ReplaceNode: Ping reply received from %s.",
-                    message->getRemoteNode()->toString().c_str());
+  A2_LOG_INFO(fmt("ReplaceNode: Ping reply received from %s.",
+                  message->getRemoteNode()->toString().c_str()));
   setFinished(true);
 }
 
@@ -84,16 +86,16 @@ void DHTReplaceNodeTask::onTimeout(const SharedHandle<DHTNode>& node)
 {
   ++numRetry_;
   if(numRetry_ >= MAX_RETRY) {
-    getLogger()->info("ReplaceNode: Ping failed %lu times. Replace %s with %s.",
-                      static_cast<unsigned long>(numRetry_),
-                      node->toString().c_str(),
-                      newNode_->toString().c_str());
+    A2_LOG_INFO(fmt("ReplaceNode: Ping failed %lu times. Replace %s with %s.",
+                    static_cast<unsigned long>(numRetry_),
+                    node->toString().c_str(),
+                    newNode_->toString().c_str()));
     node->markBad();
     bucket_->addNode(newNode_);
     setFinished(true);
   } else {
-    getLogger()->info("ReplaceNode: Ping reply timeout from %s. Try once more.",
-                      node->toString().c_str());
+    A2_LOG_INFO(fmt("ReplaceNode: Ping reply timeout from %s. Try once more.",
+                    node->toString().c_str()));
     sendMessage();
   }
 }
diff --git a/src/DHTRoutingTable.cc b/src/DHTRoutingTable.cc
index bffcad3f..a9fbd157 100644
--- a/src/DHTRoutingTable.cc
+++ b/src/DHTRoutingTable.cc
@@ -45,6 +45,7 @@
 #include "util.h"
 #include "LogFactory.h"
 #include "Logger.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -52,8 +53,7 @@ DHTRoutingTable::DHTRoutingTable(const SharedHandle<DHTNode>& localNode)
   : localNode_(localNode),
     root_(new DHTBucketTreeNode
           (SharedHandle<DHTBucket>(new DHTBucket(localNode_)))),
-    numBucket_(1),
-    logger_(LogFactory::getInstance())
+    numBucket_(1)
 {}
 
 DHTRoutingTable::~DHTRoutingTable()
@@ -73,30 +73,21 @@ bool DHTRoutingTable::addGoodNode(const SharedHandle<DHTNode>& node)
 
 bool DHTRoutingTable::addNode(const SharedHandle<DHTNode>& node, bool good)
 {
-  if(logger_->debug()) {
-    logger_->debug("Trying to add node:%s", node->toString().c_str());
-  }
+  A2_LOG_DEBUG(fmt("Trying to add node:%s", node->toString().c_str()));
   if(*localNode_ == *node) {
-    if(logger_->debug()) {
-      logger_->debug("Adding node with the same ID with localnode is not"
-                     " allowed.");
-    }
+    A2_LOG_DEBUG("Adding node with the same ID with localnode is not allowed.");
     return false;
   }
   DHTBucketTreeNode* treeNode = dht::findTreeNodeFor(root_, node->getID());
   while(1) {
     const SharedHandle<DHTBucket>& bucket = treeNode->getBucket();
     if(bucket->addNode(node)) {
-      if(logger_->debug()) {
-        logger_->debug("Added DHTNode.");
-      }
+      A2_LOG_DEBUG("Added DHTNode.");
       return true;
     } else if(bucket->splitAllowed()) {
-      if(logger_->debug()) {
-        logger_->debug("Splitting bucket. Range:%s-%s",
+      A2_LOG_DEBUG(fmt("Splitting bucket. Range:%s-%s",
                        util::toHex(bucket->getMinID(), DHT_ID_LENGTH).c_str(),
-                       util::toHex(bucket->getMaxID(), DHT_ID_LENGTH).c_str());
-      }
+                       util::toHex(bucket->getMaxID(), DHT_ID_LENGTH).c_str()));
       treeNode->split();
       ++numBucket_;
       if(treeNode->getLeft()->isInRange(node->getID())) {
@@ -107,9 +98,7 @@ bool DHTRoutingTable::addNode(const SharedHandle<DHTNode>& node, bool good)
     } else {
       if(good) {
         bucket->cacheNode(node);
-        if(logger_->debug()) {
-          logger_->debug("Cached node=%s", node->toString().c_str());
-        }
+        A2_LOG_DEBUG(fmt("Cached node=%s", node->toString().c_str()));
       }
       return false;
     }
diff --git a/src/DHTRoutingTable.h b/src/DHTRoutingTable.h
index 3c2c7af8..231c4034 100644
--- a/src/DHTRoutingTable.h
+++ b/src/DHTRoutingTable.h
@@ -49,7 +49,6 @@ class DHTBucket;
 class DHTTaskQueue;
 class DHTTaskFactory;
 class DHTBucketTreeNode;
-class Logger;
 
 class DHTRoutingTable {
 private:
@@ -63,8 +62,6 @@ private:
 
   SharedHandle<DHTTaskFactory> taskFactory_;
 
-  Logger* logger_;
-
   bool addNode(const SharedHandle<DHTNode>& node, bool good);
 public:
   DHTRoutingTable(const SharedHandle<DHTNode>& localNode);
diff --git a/src/DHTSetup.cc b/src/DHTSetup.cc
index 2ac7467e..46286186 100644
--- a/src/DHTSetup.cc
+++ b/src/DHTSetup.cc
@@ -69,10 +69,11 @@
 #include "RecoverableException.h"
 #include "a2functional.h"
 #include "DownloadEngine.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTSetup::DHTSetup():logger_(LogFactory::getInstance()) {}
+DHTSetup::DHTSetup() {}
 
 DHTSetup::~DHTSetup() {}
 
@@ -105,8 +106,10 @@ void DHTSetup::setup
       deserializer.deserialize(in);
       localNode = deserializer.getLocalNode();
     } catch(RecoverableException& e) {
-      logger_->error("Exception caught while loading DHT routing table from %s",
-                     e, dhtFile.c_str());
+      A2_LOG_ERROR_EX
+        (fmt("Exception caught while loading DHT routing table from %s",
+             dhtFile.c_str()),
+         e);
     }
     if(!localNode) {
       localNode.reset(new DHTNode());
@@ -125,10 +128,8 @@ void DHTSetup::setup
       }
       localNode->setPort(port);
     }
-    if(logger_->debug()) {
-      logger_->debug("Initialized local node ID=%s",
-                     util::toHex(localNode->getID(), DHT_ID_LENGTH).c_str());
-    }
+    A2_LOG_DEBUG(fmt("Initialized local node ID=%s",
+                     util::toHex(localNode->getID(), DHT_ID_LENGTH).c_str()));
     SharedHandle<DHTRoutingTable> routingTable(new DHTRoutingTable(localNode));
 
     SharedHandle<DHTMessageFactoryImpl> factory
@@ -240,7 +241,7 @@ void DHTSetup::setup
         tempCommands->push_back(command);
       }
     } else {
-      logger_->info("No DHT entry point specified.");
+      A2_LOG_INFO("No DHT entry point specified.");
     }
     {
       DHTInteractionCommand* command =
@@ -288,8 +289,9 @@ void DHTSetup::setup
     commands.insert(commands.end(), tempCommands->begin(), tempCommands->end());
     tempCommands->clear();
   } catch(RecoverableException& e) {
-    logger_->error("Exception caught while initializing DHT functionality."
-                   " DHT is disabled.", e);
+    A2_LOG_ERROR_EX(fmt("Exception caught while initializing DHT functionality."
+                        " DHT is disabled."),
+                    e);
     if(family == AF_INET) {
       DHTRegistry::clearData();
     } else {
diff --git a/src/DHTSetup.h b/src/DHTSetup.h
index 40a031c2..1d111fa0 100644
--- a/src/DHTSetup.h
+++ b/src/DHTSetup.h
@@ -39,13 +39,11 @@
 #include <vector>
 
 namespace aria2 {
-class Logger;
+
 class DownloadEngine;
 class Command;
 
 class DHTSetup {
-private:
-  Logger* logger_;
 public:
   DHTSetup();
 
diff --git a/src/DHTTaskExecutor.cc b/src/DHTTaskExecutor.cc
index 7227f17f..87949110 100644
--- a/src/DHTTaskExecutor.cc
+++ b/src/DHTTaskExecutor.cc
@@ -40,12 +40,13 @@
 #include "Logger.h"
 #include "LogFactory.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DHTTaskExecutor::DHTTaskExecutor(size_t numConcurrent):
-  numConcurrent_(numConcurrent),
-  logger_(LogFactory::getInstance()) {}
+DHTTaskExecutor::DHTTaskExecutor(size_t numConcurrent)
+  : numConcurrent_(numConcurrent)
+{}
 
 DHTTaskExecutor::~DHTTaskExecutor() {}
 
@@ -64,11 +65,9 @@ void DHTTaskExecutor::update()
       --r;
     }
   }
-  if(logger_->debug()) {
-    logger_->debug("Executing %u Task(s). Queue has %u task(s).",
+  A2_LOG_DEBUG(fmt("Executing %u Task(s). Queue has %u task(s).",
                    static_cast<unsigned int>(getExecutingTaskSize()),
-                   static_cast<unsigned int>(getQueueSize()));
-  }
+                   static_cast<unsigned int>(getQueueSize())));
 }
 
 } // namespace aria2
diff --git a/src/DHTTaskExecutor.h b/src/DHTTaskExecutor.h
index 436c8dff..f43b3dad 100644
--- a/src/DHTTaskExecutor.h
+++ b/src/DHTTaskExecutor.h
@@ -45,14 +45,12 @@
 namespace aria2 {
 
 class DHTTask;
-class Logger;
 
 class DHTTaskExecutor {
 private:
   size_t numConcurrent_;
   std::vector<SharedHandle<DHTTask> > execTasks_;
   std::deque<SharedHandle<DHTTask> > queue_;
-  Logger* logger_;
 public:
   DHTTaskExecutor(size_t numConcurrent);
 
diff --git a/src/DHTTaskFactoryImpl.cc b/src/DHTTaskFactoryImpl.cc
index 3119efb9..d4488560 100644
--- a/src/DHTTaskFactoryImpl.cc
+++ b/src/DHTTaskFactoryImpl.cc
@@ -38,8 +38,6 @@
 #include "DHTMessageDispatcher.h"
 #include "DHTMessageFactory.h"
 #include "DHTTaskQueue.h"
-#include "LogFactory.h"
-#include "Logger.h"
 #include "DHTPingTask.h"
 #include "DHTNodeLookupTask.h"
 #include "DHTBucketRefreshTask.h"
@@ -53,13 +51,13 @@
 
 namespace aria2 {
 
-DHTTaskFactoryImpl::DHTTaskFactoryImpl():
-  routingTable_(0),
-  dispatcher_(0),
-  factory_(0),
-  taskQueue_(0),
-  timeout_(DHT_MESSAGE_TIMEOUT),
-  logger_(LogFactory::getInstance()) {}
+DHTTaskFactoryImpl::DHTTaskFactoryImpl()
+  : routingTable_(0),
+    dispatcher_(0),
+    factory_(0),
+    taskQueue_(0),
+    timeout_(DHT_MESSAGE_TIMEOUT)
+{}
 
 DHTTaskFactoryImpl::~DHTTaskFactoryImpl() {}
 
diff --git a/src/DHTTaskFactoryImpl.h b/src/DHTTaskFactoryImpl.h
index 032fb0fa..e90219aa 100644
--- a/src/DHTTaskFactoryImpl.h
+++ b/src/DHTTaskFactoryImpl.h
@@ -46,7 +46,6 @@ class DHTMessageDispatcher;
 class DHTMessageFactory;
 class DHTTaskQueue;
 class DHTAbstractTask;
-class Logger;
 
 class DHTTaskFactoryImpl:public DHTTaskFactory {
 private:
@@ -62,8 +61,6 @@ private:
 
   time_t timeout_;
 
-  Logger* logger_;
-
   void setCommonProperty(const SharedHandle<DHTAbstractTask>& task);
 public:
   DHTTaskFactoryImpl();
diff --git a/src/DHTTaskQueueImpl.cc b/src/DHTTaskQueueImpl.cc
index 02804ece..505fb010 100644
--- a/src/DHTTaskQueueImpl.cc
+++ b/src/DHTTaskQueueImpl.cc
@@ -43,27 +43,21 @@ namespace {
 const size_t NUM_CONCURRENT_TASK = 5;
 } // namespace
 
-DHTTaskQueueImpl::DHTTaskQueueImpl():
-  periodicTaskQueue1_(NUM_CONCURRENT_TASK),
-  periodicTaskQueue2_(NUM_CONCURRENT_TASK),
-  immediateTaskQueue_(NUM_CONCURRENT_TASK),
-  logger_(LogFactory::getInstance()) {}
+DHTTaskQueueImpl::DHTTaskQueueImpl()
+  : periodicTaskQueue1_(NUM_CONCURRENT_TASK),
+    periodicTaskQueue2_(NUM_CONCURRENT_TASK),
+    immediateTaskQueue_(NUM_CONCURRENT_TASK)
+{}
 
 DHTTaskQueueImpl::~DHTTaskQueueImpl() {}
 
 void DHTTaskQueueImpl::executeTask()
 {
-  if(logger_->debug()) {
-    logger_->debug("Updating periodicTaskQueue1");
-  }
+  A2_LOG_DEBUG("Updating periodicTaskQueue1");
   periodicTaskQueue1_.update();
-  if(logger_->debug()) {
-    logger_->debug("Updating periodicTaskQueue2");
-  }
+  A2_LOG_DEBUG("Updating periodicTaskQueue2");
   periodicTaskQueue2_.update();
-  if(logger_->debug()) {
-    logger_->debug("Updating immediateTaskQueue");
-  }
+  A2_LOG_DEBUG("Updating immediateTaskQueue");
   immediateTaskQueue_.update();
 }
 
diff --git a/src/DHTTaskQueueImpl.h b/src/DHTTaskQueueImpl.h
index c293bff0..87c0eaf0 100644
--- a/src/DHTTaskQueueImpl.h
+++ b/src/DHTTaskQueueImpl.h
@@ -40,8 +40,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class DHTTaskQueueImpl:public DHTTaskQueue {
 private:
   DHTTaskExecutor periodicTaskQueue1_;
@@ -49,8 +47,6 @@ private:
   DHTTaskExecutor periodicTaskQueue2_;
 
   DHTTaskExecutor immediateTaskQueue_;
-
-  Logger* logger_;
 public:
   DHTTaskQueueImpl();
 
diff --git a/src/DHTTokenUpdateCommand.cc b/src/DHTTokenUpdateCommand.cc
index 8253bc88..176cb6a9 100644
--- a/src/DHTTokenUpdateCommand.cc
+++ b/src/DHTTokenUpdateCommand.cc
@@ -39,13 +39,14 @@
 #include "RecoverableException.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 
 namespace aria2 {
 
-DHTTokenUpdateCommand::DHTTokenUpdateCommand(cuid_t cuid,
-                                             DownloadEngine* e,
-                                             time_t interval):
-  TimeBasedCommand(cuid, e, interval) {}
+DHTTokenUpdateCommand::DHTTokenUpdateCommand
+(cuid_t cuid, DownloadEngine* e, time_t interval)
+  : TimeBasedCommand(cuid, e, interval)
+{}
 
 DHTTokenUpdateCommand::~DHTTokenUpdateCommand() {}
 
@@ -62,7 +63,7 @@ void DHTTokenUpdateCommand::process()
   try {
     tokenTracker_->updateTokenSecret();
   } catch(RecoverableException& e) {
-    getLogger()->error(EX_EXCEPTION_CAUGHT, e);
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
   }
 }
 
diff --git a/src/DefaultBtAnnounce.cc b/src/DefaultBtAnnounce.cc
index 5f65d5e7..a7742005 100644
--- a/src/DefaultBtAnnounce.cc
+++ b/src/DefaultBtAnnounce.cc
@@ -47,6 +47,7 @@
 #include "Peer.h"
 #include "Option.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "A2STR.h"
 #include "bencode2.h"
 #include "bittorrent_helper.h"
@@ -57,19 +58,18 @@ namespace aria2 {
 
 DefaultBtAnnounce::DefaultBtAnnounce
 (const SharedHandle<DownloadContext>& downloadContext,
- const Option* option):
-  downloadContext_(downloadContext),
-  trackers_(0),
-  prevAnnounceTimer_(0),
-  interval_(DEFAULT_ANNOUNCE_INTERVAL),
-  minInterval_(DEFAULT_ANNOUNCE_INTERVAL),
-  userDefinedInterval_(0),
-  complete_(0),
-  incomplete_(0),
-  announceList_(bittorrent::getTorrentAttrs(downloadContext)->announceList),
-  option_(option),
-  logger_(LogFactory::getInstance()),
-  randomizer_(SimpleRandomizer::getInstance())
+ const Option* option)
+  : downloadContext_(downloadContext),
+    trackers_(0),
+    prevAnnounceTimer_(0),
+    interval_(DEFAULT_ANNOUNCE_INTERVAL),
+    minInterval_(DEFAULT_ANNOUNCE_INTERVAL),
+    userDefinedInterval_(0),
+    complete_(0),
+    incomplete_(0),
+    announceList_(bittorrent::getTorrentAttrs(downloadContext)->announceList),
+    option_(option),
+    randomizer_(SimpleRandomizer::getInstance())
 {}
 
 DefaultBtAnnounce::~DefaultBtAnnounce() {
@@ -218,9 +218,7 @@ void
 DefaultBtAnnounce::processAnnounceResponse(const unsigned char* trackerResponse,
                                            size_t trackerResponseLength)
 {
-  if(logger_->debug()) {
-    logger_->debug("Now processing tracker response.");
-  }
+  A2_LOG_DEBUG("Now processing tracker response.");
   SharedHandle<ValueBase> decodedValue =
     bencode2::decode(trackerResponse, trackerResponseLength);
   const Dict* dict = asDict(decodedValue);
@@ -234,28 +232,22 @@ DefaultBtAnnounce::processAnnounceResponse(const unsigned char* trackerResponse,
   }
   const String* warn = asString(dict->get(BtAnnounce::WARNING_MESSAGE));
   if(warn) {
-    logger_->warn(MSG_TRACKER_WARNING_MESSAGE, warn->s().c_str());
+    A2_LOG_WARN(fmt(MSG_TRACKER_WARNING_MESSAGE, warn->s().c_str()));
   }
   const String* tid = asString(dict->get(BtAnnounce::TRACKER_ID));
   if(tid) {
     trackerId_ = tid->s();
-    if(logger_->debug()) {
-      logger_->debug("Tracker ID:%s", trackerId_.c_str());
-    }
+    A2_LOG_DEBUG(fmt("Tracker ID:%s", trackerId_.c_str()));
   }
   const Integer* ival = asInteger(dict->get(BtAnnounce::INTERVAL));
   if(ival && ival->i() > 0) {
     interval_ = ival->i();
-    if(logger_->debug()) {
-      logger_->debug("Interval:%ld", static_cast<long int>(interval_));
-    }
+    A2_LOG_DEBUG(fmt("Interval:%ld", static_cast<long int>(interval_)));
   }
   const Integer* mival = asInteger(dict->get(BtAnnounce::MIN_INTERVAL));
   if(mival && mival->i() > 0) {
     minInterval_ = mival->i();
-    if(logger_->debug()) {
-      logger_->debug("Min interval:%ld", static_cast<long int>(minInterval_));
-    }
+    A2_LOG_DEBUG(fmt("Min interval:%ld", static_cast<long int>(minInterval_)));
     minInterval_ = std::min(minInterval_, interval_);
   } else {
     // Use interval as a minInterval if minInterval is not supplied.
@@ -264,20 +256,16 @@ DefaultBtAnnounce::processAnnounceResponse(const unsigned char* trackerResponse,
   const Integer* comp = asInteger(dict->get(BtAnnounce::COMPLETE));
   if(comp) {
     complete_ = comp->i();
-    if(logger_->debug()) {
-      logger_->debug("Complete:%d", complete_);
-    }
+    A2_LOG_DEBUG(fmt("Complete:%d", complete_));
   }
   const Integer* incomp = asInteger(dict->get(BtAnnounce::INCOMPLETE));
   if(incomp) {
     incomplete_ = incomp->i();
-    if(logger_->debug()) {
-      logger_->debug("Incomplete:%d", incomplete_);
-    }
+    A2_LOG_DEBUG(fmt("Incomplete:%d", incomplete_));
   }
   const SharedHandle<ValueBase>& peerData = dict->get(BtAnnounce::PEERS);
   if(!peerData) {
-    logger_->info(MSG_NO_PEER_LIST_RECEIVED);
+    A2_LOG_INFO(MSG_NO_PEER_LIST_RECEIVED);
   } else {
     if(!btRuntime_->isHalt() && btRuntime_->lessThanMinPeers()) {
       std::vector<SharedHandle<Peer> > peers;
@@ -287,7 +275,7 @@ DefaultBtAnnounce::processAnnounceResponse(const unsigned char* trackerResponse,
   }
   const SharedHandle<ValueBase>& peer6Data = dict->get(BtAnnounce::PEERS6);
   if(!peer6Data) {
-    logger_->info("No peers6 received.");
+    A2_LOG_INFO("No peers6 received.");
   } else {
     if(!btRuntime_->isHalt() && btRuntime_->lessThanMinPeers()) {
       std::vector<SharedHandle<Peer> > peers;
diff --git a/src/DefaultBtAnnounce.h b/src/DefaultBtAnnounce.h
index 027dfad8..f2591339 100644
--- a/src/DefaultBtAnnounce.h
+++ b/src/DefaultBtAnnounce.h
@@ -43,7 +43,6 @@ namespace aria2 {
 
 class DownloadContext;
 class Option;
-class Logger;
 class BtRuntime;
 class PieceStorage;
 class PeerStorage;
@@ -62,7 +61,6 @@ private:
   AnnounceList announceList_;
   std::string trackerId_;
   const Option* option_;
-  Logger* logger_;
   SharedHandle<Randomizer> randomizer_;
   SharedHandle<BtRuntime> btRuntime_;
   SharedHandle<PieceStorage> pieceStorage_;
diff --git a/src/DefaultBtInteractive.cc b/src/DefaultBtInteractive.cc
index 1fe827b8..792cc3d8 100644
--- a/src/DefaultBtInteractive.cc
+++ b/src/DefaultBtInteractive.cc
@@ -67,6 +67,7 @@
 #include "Logger.h"
 #include "LogFactory.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "RequestGroup.h"
 #include "RequestGroupMan.h"
 #include "bittorrent_helper.h"
@@ -79,25 +80,23 @@ namespace aria2 {
 DefaultBtInteractive::DefaultBtInteractive
 (const SharedHandle<DownloadContext>& downloadContext,
  const SharedHandle<Peer>& peer)
-  :
-  downloadContext_(downloadContext),
-  peer_(peer),
-  metadataGetMode_(false),
-  localNode_(0),
-  logger_(LogFactory::getInstance()),
-  allowedFastSetSize_(10),
-  haveTimer_(global::wallclock),
-  keepAliveTimer_(global::wallclock),
-  floodingTimer_(global::wallclock),
-  inactiveTimer_(global::wallclock),
-  pexTimer_(global::wallclock),
-  perSecTimer_(global::wallclock),
-  keepAliveInterval_(120),
-  utPexEnabled_(false),
-  dhtEnabled_(false),
-  numReceivedMessage_(0),
-  maxOutstandingRequest_(DEFAULT_MAX_OUTSTANDING_REQUEST),
-  requestGroupMan_(0)
+  : downloadContext_(downloadContext),
+    peer_(peer),
+    metadataGetMode_(false),
+    localNode_(0),
+    allowedFastSetSize_(10),
+    haveTimer_(global::wallclock),
+    keepAliveTimer_(global::wallclock),
+    floodingTimer_(global::wallclock),
+    inactiveTimer_(global::wallclock),
+    pexTimer_(global::wallclock),
+    perSecTimer_(global::wallclock),
+    keepAliveInterval_(120),
+    utPexEnabled_(false),
+    dhtEnabled_(false),
+    numReceivedMessage_(0),
+    maxOutstandingRequest_(DEFAULT_MAX_OUTSTANDING_REQUEST),
+    requestGroupMan_(0)
 {}
 
 DefaultBtInteractive::~DefaultBtInteractive() {}
@@ -139,30 +138,22 @@ BtMessageHandle DefaultBtInteractive::receiveHandshake(bool quickReply) {
     
   if(message->isFastExtensionSupported()) {
     peer_->setFastExtensionEnabled(true);
-    if(logger_->info()) {
-      logger_->info(MSG_FAST_EXTENSION_ENABLED, util::itos(cuid_).c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_FAST_EXTENSION_ENABLED, util::itos(cuid_).c_str()));
   }
   if(message->isExtendedMessagingEnabled()) {
     peer_->setExtendedMessagingEnabled(true);
     if(!utPexEnabled_) {
       extensionMessageRegistry_->removeExtension("ut_pex");
     }
-    if(logger_->info()) {
-      logger_->info(MSG_EXTENDED_MESSAGING_ENABLED, util::itos(cuid_).c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_EXTENDED_MESSAGING_ENABLED, util::itos(cuid_).c_str()));
   }
   if(message->isDHTEnabled()) {
     peer_->setDHTEnabled(true);
-    if(logger_->info()) {
-      logger_->info(MSG_DHT_ENABLED_PEER, util::itos(cuid_).c_str());
-    }
-  }
-  if(logger_->info()) {
-    logger_->info(MSG_RECEIVE_PEER_MESSAGE, util::itos(cuid_).c_str(),
-                 peer_->getIPAddress().c_str(), peer_->getPort(),
-                 message->toString().c_str());
+    A2_LOG_INFO(fmt(MSG_DHT_ENABLED_PEER, util::itos(cuid_).c_str()));
   }
+  A2_LOG_INFO(fmt(MSG_RECEIVE_PEER_MESSAGE, util::itos(cuid_).c_str(),
+                  peer_->getIPAddress().c_str(), peer_->getPort(),
+                  message->toString().c_str()));
   return message;
 }
 
@@ -296,11 +287,10 @@ size_t DefaultBtInteractive::receiveMessages() {
       break;
     }
     ++msgcount;
-    if(logger_->info()) {
-      logger_->info(MSG_RECEIVE_PEER_MESSAGE, util::itos(cuid_).c_str(),
-                   peer_->getIPAddress().c_str(), peer_->getPort(),
-                   message->toString().c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_RECEIVE_PEER_MESSAGE,
+                    util::itos(cuid_).c_str(),
+                    peer_->getIPAddress().c_str(), peer_->getPort(),
+                    message->toString().c_str()));
     message->doReceivedAction();
 
     switch(message->getId()) {
@@ -338,17 +328,13 @@ size_t DefaultBtInteractive::receiveMessages() {
 void DefaultBtInteractive::decideInterest() {
   if(pieceStorage_->hasMissingPiece(peer_)) {
     if(!peer_->amInterested()) {
-      if(logger_->debug()) {
-        logger_->debug(MSG_PEER_INTERESTED, util::itos(cuid_).c_str());
-      }
+      A2_LOG_DEBUG(fmt(MSG_PEER_INTERESTED, util::itos(cuid_).c_str()));
       dispatcher_->
         addMessageToQueue(messageFactory_->createInterestedMessage());
     }
   } else {
     if(peer_->amInterested()) {
-      if(logger_->debug()) {
-        logger_->debug(MSG_PEER_NOT_INTERESTED, util::itos(cuid_).c_str());
-      }
+      A2_LOG_DEBUG(fmt(MSG_PEER_NOT_INTERESTED, util::itos(cuid_).c_str()));
       dispatcher_->
         addMessageToQueue(messageFactory_->createNotInterestedMessage());
     }
@@ -425,10 +411,8 @@ void DefaultBtInteractive::cancelAllPiece() {
       utMetadataRequestTracker_->getAllTrackedIndex();
     for(std::vector<size_t>::const_iterator i = metadataRequests.begin(),
           eoi = metadataRequests.end(); i != eoi; ++i) {
-      if(logger_->debug()) {
-        logger_->debug("Cancel metadata: piece=%lu",
-                      static_cast<unsigned long>(*i));
-      }
+      A2_LOG_DEBUG(fmt("Cancel metadata: piece=%lu",
+                       static_cast<unsigned long>(*i)));
       pieceStorage_->cancelPiece(pieceStorage_->getPiece(*i));
     }
   }
diff --git a/src/DefaultBtInteractive.h b/src/DefaultBtInteractive.h
index e639e242..fdbd892a 100644
--- a/src/DefaultBtInteractive.h
+++ b/src/DefaultBtInteractive.h
@@ -58,7 +58,6 @@ class PeerConnection;
 class ExtensionMessageFactory;
 class ExtensionMessageRegistry;
 class DHTNode;
-class Logger;
 class RequestGroupMan;
 class UTMetadataRequestFactory;
 class UTMetadataRequestTracker;
@@ -126,7 +125,6 @@ private:
 
   DHTNode* localNode_;
 
-  Logger* logger_;
   size_t allowedFastSetSize_;
   Timer haveTimer_;
   Timer keepAliveTimer_;
diff --git a/src/DefaultBtMessageDispatcher.cc b/src/DefaultBtMessageDispatcher.cc
index 7732fbb9..92d8d3f7 100644
--- a/src/DefaultBtMessageDispatcher.cc
+++ b/src/DefaultBtMessageDispatcher.cc
@@ -55,21 +55,20 @@
 #include "RequestGroupMan.h"
 #include "RequestGroup.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DefaultBtMessageDispatcher::DefaultBtMessageDispatcher():
-  cuid(0),
-  messageFactory_(0),
-  requestGroupMan_(0),
-  requestTimeout_(0),
-  logger_(LogFactory::getInstance()) {}
+DefaultBtMessageDispatcher::DefaultBtMessageDispatcher()
+  : cuid(0),
+    messageFactory_(0),
+    requestGroupMan_(0),
+    requestTimeout_(0)
+{}
 
 DefaultBtMessageDispatcher::~DefaultBtMessageDispatcher()
 {
-  if(logger_->debug()) {
-    logger_->debug("DefaultBtMessageDispatcher::deleted");
-  }
+  A2_LOG_DEBUG("DefaultBtMessageDispatcher::deleted");
 }
 
 void DefaultBtMessageDispatcher::addMessageToQueue
@@ -147,22 +146,19 @@ class AbortOutstandingRequest {
 private:
   SharedHandle<Piece> piece_;
   cuid_t cuid_;
-  Logger* logger_;
 public:
-  AbortOutstandingRequest(const SharedHandle<Piece>& piece, cuid_t cuid):
-    piece_(piece),
-    cuid_(cuid),
-    logger_(LogFactory::getInstance()) {}
+  AbortOutstandingRequest(const SharedHandle<Piece>& piece, cuid_t cuid)
+    : piece_(piece),
+      cuid_(cuid)
+  {}
 
   void operator()(const RequestSlot& slot) const
   {
-    if(logger_->debug()) {
-      logger_->debug(MSG_DELETING_REQUEST_SLOT,
+    A2_LOG_DEBUG(fmt(MSG_DELETING_REQUEST_SLOT,
                      util::itos(cuid_).c_str(),
                      static_cast<unsigned long>(slot.getIndex()),
                      slot.getBegin(),
-                     static_cast<unsigned long>(slot.getBlockIndex()));
-    }
+                     static_cast<unsigned long>(slot.getBlockIndex())));
     piece_->cancelBlock(slot.getBlockIndex());
   }
 };
@@ -196,26 +192,24 @@ private:
   cuid_t cuid_;
   SharedHandle<Peer> peer_;
   SharedHandle<PieceStorage> pieceStorage_;
-  Logger* logger_;
 public:
-  ProcessChokedRequestSlot(cuid_t cuid,
-                           const SharedHandle<Peer>& peer,
-                           const SharedHandle<PieceStorage>& pieceStorage):
-    cuid_(cuid),
-    peer_(peer),
-    pieceStorage_(pieceStorage),
-    logger_(LogFactory::getInstance()) {}
+  ProcessChokedRequestSlot
+  (cuid_t cuid,
+   const SharedHandle<Peer>& peer,
+   const SharedHandle<PieceStorage>& pieceStorage)
+    : cuid_(cuid),
+      peer_(peer),
+      pieceStorage_(pieceStorage)
+  {}
   
   void operator()(const RequestSlot& slot) const
   {
     if(!peer_->isInPeerAllowedIndexSet(slot.getIndex())) {
-      if(logger_->debug()) {
-        logger_->debug(MSG_DELETING_REQUEST_SLOT_CHOKED,
+      A2_LOG_DEBUG(fmt(MSG_DELETING_REQUEST_SLOT_CHOKED,
                        util::itos(cuid_).c_str(),
                        static_cast<unsigned long>(slot.getIndex()),
                        slot.getBegin(),
-                       static_cast<unsigned long>(slot.getBlockIndex()));
-      }
+                       static_cast<unsigned long>(slot.getBlockIndex())));
       SharedHandle<Piece> piece = pieceStorage_->getPiece(slot.getIndex());
       piece->cancelBlock(slot.getBlockIndex());
     }
@@ -270,41 +264,37 @@ private:
   BtMessageDispatcher* messageDispatcher_;
   BtMessageFactory* messageFactory_;
   time_t requestTimeout_;
-  Logger* logger_;
 public:
-  ProcessStaleRequestSlot(cuid_t cuid, const SharedHandle<Peer>& peer,
-                          const SharedHandle<PieceStorage>& pieceStorage,
-                          BtMessageDispatcher* dispatcher,
-                          BtMessageFactory* factory,
-                          time_t requestTimeout):
-    cuid_(cuid),
-    peer_(peer),
-    pieceStorage_(pieceStorage),
-    messageDispatcher_(dispatcher),
-    messageFactory_(factory),
-    requestTimeout_(requestTimeout),
-    logger_(LogFactory::getInstance()) {}
+  ProcessStaleRequestSlot
+  (cuid_t cuid, const SharedHandle<Peer>& peer,
+   const SharedHandle<PieceStorage>& pieceStorage,
+   BtMessageDispatcher* dispatcher,
+   BtMessageFactory* factory,
+   time_t requestTimeout)
+    : cuid_(cuid),
+      peer_(peer),
+      pieceStorage_(pieceStorage),
+      messageDispatcher_(dispatcher),
+      messageFactory_(factory),
+      requestTimeout_(requestTimeout)
+  {}
 
   void operator()(const RequestSlot& slot)
   {
     if(slot.isTimeout(requestTimeout_)) {
-      if(logger_->debug()) {
-        logger_->debug(MSG_DELETING_REQUEST_SLOT_TIMEOUT,
+      A2_LOG_DEBUG(fmt(MSG_DELETING_REQUEST_SLOT_TIMEOUT,
                        util::itos(cuid_).c_str(),
                        static_cast<unsigned long>(slot.getIndex()),
                        slot.getBegin(),
-                       static_cast<unsigned long>(slot.getBlockIndex()));
-      }
+                       static_cast<unsigned long>(slot.getBlockIndex())));
       slot.getPiece()->cancelBlock(slot.getBlockIndex());
       peer_->snubbing(true);
     } else if(slot.getPiece()->hasBlock(slot.getBlockIndex())) {
-      if(logger_->debug()) {
-        logger_->debug(MSG_DELETING_REQUEST_SLOT_ACQUIRED,
+      A2_LOG_DEBUG(fmt(MSG_DELETING_REQUEST_SLOT_ACQUIRED,
                        util::itos(cuid_).c_str(),
                        static_cast<unsigned long>(slot.getIndex()),
                        slot.getBegin(),
-                       static_cast<unsigned long>(slot.getBlockIndex()));
-      }
+                       static_cast<unsigned long>(slot.getBlockIndex())));
       messageDispatcher_->addMessageToQueue
         (messageFactory_->createCancelMessage(slot.getIndex(),
                                               slot.getBegin(),
diff --git a/src/DefaultBtMessageDispatcher.h b/src/DefaultBtMessageDispatcher.h
index 4f5e73d8..40b80192 100644
--- a/src/DefaultBtMessageDispatcher.h
+++ b/src/DefaultBtMessageDispatcher.h
@@ -51,7 +51,6 @@ class BtMessage;
 class BtMessageFactory;
 class Peer;
 class Piece;
-class Logger;
 class RequestGroupMan;
 
 class DefaultBtMessageDispatcher : public BtMessageDispatcher {
@@ -66,7 +65,6 @@ private:
   SharedHandle<Peer> peer_;
   RequestGroupMan* requestGroupMan_;
   time_t requestTimeout_;
-  Logger* logger_;
 public:
   DefaultBtMessageDispatcher();
 
diff --git a/src/DefaultBtMessageReceiver.h b/src/DefaultBtMessageReceiver.h
index 663610c0..5ccb8473 100644
--- a/src/DefaultBtMessageReceiver.h
+++ b/src/DefaultBtMessageReceiver.h
@@ -45,7 +45,6 @@ class Peer;
 class PeerConnection;
 class BtMessageDispatcher;
 class BtMessageFactory;
-class Logger;
 
 class DefaultBtMessageReceiver : public BtMessageReceiver {
 private:
diff --git a/src/DefaultBtProgressInfoFile.cc b/src/DefaultBtProgressInfoFile.cc
index a662465d..fae1057d 100644
--- a/src/DefaultBtProgressInfoFile.cc
+++ b/src/DefaultBtProgressInfoFile.cc
@@ -52,6 +52,7 @@
 #include "a2io.h"
 #include "DownloadFailureException.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "array_fun.h"
 #include "DownloadContext.h"
 #ifdef ENABLE_BITTORRENT
@@ -78,12 +79,11 @@ std::string createFilename
 DefaultBtProgressInfoFile::DefaultBtProgressInfoFile
 (const SharedHandle<DownloadContext>& dctx,
  const PieceStorageHandle& pieceStorage,
- const Option* option):
-  dctx_(dctx),
-  pieceStorage_(pieceStorage),
-  option_(option),
-  logger_(LogFactory::getInstance()),
-  filename_(createFilename(dctx_, getSuffix()))
+ const Option* option)
+  : dctx_(dctx),
+    pieceStorage_(pieceStorage),
+    option_(option),
+    filename_(createFilename(dctx_, getSuffix()))
 {}
 
 DefaultBtProgressInfoFile::~DefaultBtProgressInfoFile() {}
@@ -105,7 +105,7 @@ bool DefaultBtProgressInfoFile::isTorrentDownload()
 // Since version 0001, Integers are saved in binary form, network byte order.
 void DefaultBtProgressInfoFile::save()
 {
-  logger_->info(MSG_SAVING_SEGMENT_FILE, filename_.c_str());
+  A2_LOG_INFO(fmt(MSG_SAVING_SEGMENT_FILE, filename_.c_str()));
   std::string filenameTemp = filename_+"__temp";
   {
     std::ofstream o(filenameTemp.c_str(), std::ios::out|std::ios::binary);
@@ -201,7 +201,7 @@ void DefaultBtProgressInfoFile::save()
       throw DL_ABORT_EX
         (StringFormat(EX_SEGMENT_FILE_WRITE, filename_.c_str()).str());
     }
-    logger_->info(MSG_SAVED_SEGMENT_FILE);
+    A2_LOG_INFO(MSG_SAVED_SEGMENT_FILE);
   }
   if(!File(filenameTemp).renameTo(filename_)) {
     throw DL_ABORT_EX
@@ -225,7 +225,7 @@ void DefaultBtProgressInfoFile::save()
 // 2) network byte order if version == 0001
 void DefaultBtProgressInfoFile::load() 
 {
-  logger_->info(MSG_LOADING_SEGMENT_FILE, filename_.c_str());
+  A2_LOG_INFO(fmt(MSG_LOADING_SEGMENT_FILE, filename_.c_str()));
   std::ifstream in(filename_.c_str(), std::ios::in|std::ios::binary);
   if(!in) {
     throw DL_ABORT_EX
@@ -251,9 +251,7 @@ void DefaultBtProgressInfoFile::load()
   bool infoHashCheckEnabled = false;
   if(extension[3]&1 && isTorrentDownload()) {
     infoHashCheckEnabled = true;
-    if(logger_->debug()) {
-      logger_->debug("InfoHash checking enabled.");
-    }
+    A2_LOG_DEBUG("InfoHash checking enabled.");
   }
 
   uint32_t infoHashLength;
@@ -422,7 +420,7 @@ void DefaultBtProgressInfoFile::load()
     util::convertBitfield(&dest, &src);
     pieceStorage_->setBitfield(dest.getBitfield(), dest.getBitfieldLength());
   }
-  logger_->info(MSG_LOADED_SEGMENT_FILE);
+  A2_LOG_INFO(MSG_LOADED_SEGMENT_FILE);
 }
 
 void DefaultBtProgressInfoFile::removeFile()
@@ -437,10 +435,10 @@ bool DefaultBtProgressInfoFile::exists()
 {
   File f(filename_);
   if(f.isFile()) {
-    logger_->info(MSG_SEGMENT_FILE_EXISTS, filename_.c_str());
+    A2_LOG_INFO(fmt(MSG_SEGMENT_FILE_EXISTS, filename_.c_str()));
     return true;
   } else {
-    logger_->info(MSG_SEGMENT_FILE_DOES_NOT_EXIST, filename_.c_str());
+    A2_LOG_INFO(fmt(MSG_SEGMENT_FILE_DOES_NOT_EXIST, filename_.c_str()));
     return false;
   }
 }
diff --git a/src/DefaultBtProgressInfoFile.h b/src/DefaultBtProgressInfoFile.h
index 12aedb85..8f10b001 100644
--- a/src/DefaultBtProgressInfoFile.h
+++ b/src/DefaultBtProgressInfoFile.h
@@ -43,7 +43,6 @@ class DownloadContext;
 class PieceStorage;
 class PeerStorage;
 class BtRuntime;
-class Logger;
 class Option;
 
 class DefaultBtProgressInfoFile : public BtProgressInfoFile {
@@ -55,7 +54,6 @@ private:
   SharedHandle<BtRuntime> btRuntime_;
 #endif // ENABLE_BITTORRENT
   const Option* option_;
-  Logger* logger_;
   std::string filename_;
 
   bool isTorrentDownload();
diff --git a/src/DefaultBtRequestFactory.cc b/src/DefaultBtRequestFactory.cc
index 070775af..73d39cef 100644
--- a/src/DefaultBtRequestFactory.cc
+++ b/src/DefaultBtRequestFactory.cc
@@ -47,25 +47,16 @@
 #include "a2functional.h"
 #include "SimpleRandomizer.h"
 #include "array_fun.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-DefaultBtRequestFactory::DefaultBtRequestFactory():
-  dispatcher_(0),
-  messageFactory_(0),
-  logger_(LogFactory::getInstance())
-{
-  if(logger_->debug()) {
-    logger_->debug("DefaultBtRequestFactory::instantiated");
-  }
-}
+DefaultBtRequestFactory::DefaultBtRequestFactory()
+  : dispatcher_(0),
+    messageFactory_(0)
+{}
 
-DefaultBtRequestFactory::~DefaultBtRequestFactory()
-{
-  if(logger_->debug()) {
-    logger_->debug("DefaultBtRequestFactory::deleted");
-  }
-}
+DefaultBtRequestFactory::~DefaultBtRequestFactory() {}
 
 void DefaultBtRequestFactory::addTargetPiece(const SharedHandle<Piece>& piece)
 {
@@ -176,14 +167,12 @@ void DefaultBtRequestFactory::createRequestMessages
       getnum -= blockIndexes.size();
       for(std::vector<size_t>::const_iterator i = blockIndexes.begin(),
             eoi2 = blockIndexes.end(); i != eoi2; ++i) {
-        if(logger_->debug()) {
-          logger_->debug
-            ("Creating RequestMessage index=%lu, begin=%u,"
-             " blockIndex=%lu",
-             static_cast<unsigned long>(piece->getIndex()),
-             static_cast<unsigned int>((*i)*piece->getBlockLength()),
-             static_cast<unsigned long>(*i));
-        }
+        A2_LOG_DEBUG
+          (fmt("Creating RequestMessage index=%lu, begin=%u,"
+               " blockIndex=%lu",
+               static_cast<unsigned long>(piece->getIndex()),
+               static_cast<unsigned int>((*i)*piece->getBlockLength()),
+               static_cast<unsigned long>(*i)));
         requests.push_back
           (messageFactory_->createRequestMessage(piece, *i));
       }
@@ -222,14 +211,12 @@ void DefaultBtRequestFactory::createRequestMessagesOnEndGame
       const size_t& blockIndex = *bitr;
       if(!dispatcher_->isOutstandingRequest(piece->getIndex(),
                                            blockIndex)) {
-        if(logger_->debug()) {
-          logger_->debug
-            ("Creating RequestMessage index=%lu, begin=%u,"
-             " blockIndex=%lu",
-             static_cast<unsigned long>(piece->getIndex()),
-             static_cast<unsigned int>(blockIndex*piece->getBlockLength()),
-             static_cast<unsigned long>(blockIndex));
-        }
+        A2_LOG_DEBUG
+          (fmt("Creating RequestMessage index=%lu, begin=%u,"
+               " blockIndex=%lu",
+               static_cast<unsigned long>(piece->getIndex()),
+               static_cast<unsigned int>(blockIndex*piece->getBlockLength()),
+               static_cast<unsigned long>(blockIndex)));
         requests.push_back(messageFactory_->createRequestMessage
                            (piece, blockIndex));
       }
diff --git a/src/DefaultBtRequestFactory.h b/src/DefaultBtRequestFactory.h
index 3c2b3492..33016dcb 100644
--- a/src/DefaultBtRequestFactory.h
+++ b/src/DefaultBtRequestFactory.h
@@ -48,7 +48,6 @@ class Peer;
 class BtMessageDispatcher;
 class BtMessageFactory;
 class Piece;
-class Logger;
 
 class DefaultBtRequestFactory : public BtRequestFactory {
 private:
@@ -57,7 +56,6 @@ private:
   BtMessageDispatcher* dispatcher_;
   BtMessageFactory* messageFactory_;
   std::deque<SharedHandle<Piece> > pieces_;
-  Logger* logger_;
 public:
   DefaultBtRequestFactory();
 
diff --git a/src/DefaultExtensionMessageFactory.cc b/src/DefaultExtensionMessageFactory.cc
index a49abf2e..a69e1257 100644
--- a/src/DefaultExtensionMessageFactory.cc
+++ b/src/DefaultExtensionMessageFactory.cc
@@ -37,8 +37,6 @@
 #include "DlAbortEx.h"
 #include "HandshakeExtensionMessage.h"
 #include "UTPexExtensionMessage.h"
-#include "LogFactory.h"
-#include "Logger.h"
 #include "StringFormat.h"
 #include "PeerStorage.h"
 #include "ExtensionMessageRegistry.h"
@@ -56,18 +54,18 @@
 
 namespace aria2 {
 
-DefaultExtensionMessageFactory::DefaultExtensionMessageFactory():
-  messageFactory_(0),
-  dispatcher_(0),
-  tracker_(0),
-  logger_(LogFactory::getInstance()) {}
+DefaultExtensionMessageFactory::DefaultExtensionMessageFactory()
+  : messageFactory_(0),
+    dispatcher_(0),
+    tracker_(0)
+{}
 
 DefaultExtensionMessageFactory::DefaultExtensionMessageFactory
 (const SharedHandle<Peer>& peer,
- const SharedHandle<ExtensionMessageRegistry>& registry):
-  peer_(peer),
-  registry_(registry),
-  logger_(LogFactory::getInstance()) {}
+ const SharedHandle<ExtensionMessageRegistry>& registry)
+  : peer_(peer),
+    registry_(registry)
+{}
 
 DefaultExtensionMessageFactory::~DefaultExtensionMessageFactory() {}
 
diff --git a/src/DefaultExtensionMessageFactory.h b/src/DefaultExtensionMessageFactory.h
index e388b8d9..2ce5d772 100644
--- a/src/DefaultExtensionMessageFactory.h
+++ b/src/DefaultExtensionMessageFactory.h
@@ -41,7 +41,6 @@ namespace aria2 {
 
 class PeerStorage;
 class Peer;
-class Logger;
 class ExtensionMessageRegistry;
 class DownloadContext;
 class BtMessageFactory;
@@ -63,9 +62,6 @@ private:
   BtMessageDispatcher* dispatcher_;
 
   UTMetadataRequestTracker* tracker_;
-
-  Logger* logger_;
-
 public:
   DefaultExtensionMessageFactory();
 
diff --git a/src/DefaultPeerStorage.cc b/src/DefaultPeerStorage.cc
index 95c02527..ac390acb 100644
--- a/src/DefaultPeerStorage.cc
+++ b/src/DefaultPeerStorage.cc
@@ -46,6 +46,7 @@
 #include "PieceStorage.h"
 #include "wallclock.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -53,13 +54,12 @@ namespace {
 const int MAX_PEER_LIST_SIZE = 1024;
 } // namespace
 
-DefaultPeerStorage::DefaultPeerStorage():
-  logger_(LogFactory::getInstance()),
-  removedPeerSessionDownloadLength_(0),
-  removedPeerSessionUploadLength_(0),
-  seederStateChoke_(new BtSeederStateChoke()),
-  leecherStateChoke_(new BtLeecherStateChoke()),
-  lastTransferStatMapUpdated_(0)
+DefaultPeerStorage::DefaultPeerStorage()
+  : removedPeerSessionDownloadLength_(0),
+    removedPeerSessionUploadLength_(0),
+    seederStateChoke_(new BtSeederStateChoke()),
+    leecherStateChoke_(new BtLeecherStateChoke()),
+    lastTransferStatMapUpdated_(0)
 {}
 
 DefaultPeerStorage::~DefaultPeerStorage()
@@ -103,10 +103,9 @@ size_t calculateMaxPeerListSize(const SharedHandle<BtRuntime>& btRuntime)
 
 bool DefaultPeerStorage::addPeer(const SharedHandle<Peer>& peer) {
   if(isPeerAlreadyAdded(peer)) {
-    if(logger_->debug()) {
-      logger_->debug("Adding %s:%u is rejected because it has been already"
-                    " added.", peer->getIPAddress().c_str(), peer->getPort());
-    }
+    A2_LOG_DEBUG(fmt("Adding %s:%u is rejected because it has been already"
+                     " added.",
+                     peer->getIPAddress().c_str(), peer->getPort()));
     return false;
   }
   size_t maxPeerListSize = calculateMaxPeerListSize(btRuntime_);
@@ -123,10 +122,8 @@ void DefaultPeerStorage::addPeer(const std::vector<SharedHandle<Peer> >& peers)
         eoi = peers.end(); itr != eoi; ++itr) {
     const SharedHandle<Peer>& peer = *itr;
     if(addPeer(peer)) {
-      if(logger_->debug()) {
-        logger_->debug(MSG_ADDING_PEER,
-                       peer->getIPAddress().c_str(), peer->getPort());
-      }
+      A2_LOG_DEBUG(fmt(MSG_ADDING_PEER,
+                       peer->getIPAddress().c_str(), peer->getPort()));
     }
   }  
 }
@@ -241,9 +238,7 @@ TransferStat DefaultPeerStorage::calculateStat()
 {
   TransferStat stat;
   if(lastTransferStatMapUpdated_.differenceInMillis(global::wallclock) >= 250) {
-    if(logger_->debug()) {
-      logger_->debug("Updating TransferStat of PeerStorage");
-    }
+    A2_LOG_DEBUG("Updating TransferStat of PeerStorage");
     lastTransferStatMapUpdated_ = global::wallclock;
     peerTransferStatMap_.clear();
     std::vector<SharedHandle<Peer> > activePeers;
@@ -272,9 +267,7 @@ TransferStat DefaultPeerStorage::calculateStat()
 
 void DefaultPeerStorage::updateTransferStatFor(const SharedHandle<Peer>& peer)
 {
-  if(logger_->debug()) {
-    logger_->debug("Updating TransferStat for peer %s", peer->getID().c_str());
-  }
+  A2_LOG_DEBUG(fmt("Updating TransferStat for peer %s", peer->getID().c_str()));
   std::map<std::string, TransferStat>::iterator itr =
     peerTransferStatMap_.find(peer->getID());
   if(itr == peerTransferStatMap_.end()) {
@@ -340,10 +333,8 @@ void DefaultPeerStorage::returnPeer(const SharedHandle<Peer>& peer)
   std::deque<SharedHandle<Peer> >::iterator itr =
     std::find_if(peers_.begin(), peers_.end(), derefEqual(peer));
   if(itr == peers_.end()) {
-    if(logger_->debug()) {
-      logger_->debug("Cannot find peer %s:%u in PeerStorage.",
-                    peer->getIPAddress().c_str(), peer->getPort());
-    }
+    A2_LOG_DEBUG(fmt("Cannot find peer %s:%u in PeerStorage.",
+                     peer->getIPAddress().c_str(), peer->getPort()));
   } else {
     peers_.erase(itr);
 
diff --git a/src/DefaultPeerStorage.h b/src/DefaultPeerStorage.h
index fc62c58a..bbcf2966 100644
--- a/src/DefaultPeerStorage.h
+++ b/src/DefaultPeerStorage.h
@@ -43,7 +43,6 @@
 
 namespace aria2 {
 
-class Logger;
 class BtRuntime;
 class BtSeederStateChoke;
 class BtLeecherStateChoke;
@@ -55,7 +54,6 @@ private:
   SharedHandle<PieceStorage> pieceStorage_;
   std::deque<SharedHandle<Peer> > peers_;
   std::deque<SharedHandle<Peer> > droppedPeers_;
-  Logger* logger_;
   uint64_t removedPeerSessionDownloadLength_;
   uint64_t removedPeerSessionUploadLength_;
 
diff --git a/src/DefaultPieceStorage.cc b/src/DefaultPieceStorage.cc
index 10746f1a..72a79140 100644
--- a/src/DefaultPieceStorage.cc
+++ b/src/DefaultPieceStorage.cc
@@ -55,6 +55,7 @@
 #include "a2functional.h"
 #include "Option.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "RarestPieceSelector.h"
 #include "array_fun.h"
 #include "PieceStatMan.h"
@@ -67,20 +68,20 @@
 namespace aria2 {
 
 DefaultPieceStorage::DefaultPieceStorage
-(const SharedHandle<DownloadContext>& downloadContext, const Option* option):
-  downloadContext_(downloadContext),
-  bitfieldMan_(new BitfieldMan(downloadContext->getPieceLength(),
-                               downloadContext->getTotalLength())),
-  diskWriterFactory_(new DefaultDiskWriterFactory()),
-  endGame_(false),
-  endGamePieceNum_(END_GAME_PIECE_NUM),
-  logger_(LogFactory::getInstance()),
-  option_(option),
-  pieceStatMan_(new PieceStatMan(downloadContext->getNumPieces(), true)),
-  pieceSelector_(new RarestPieceSelector(pieceStatMan_))
+(const SharedHandle<DownloadContext>& downloadContext, const Option* option)
+ : downloadContext_(downloadContext),
+   bitfieldMan_(new BitfieldMan(downloadContext->getPieceLength(),
+                                downloadContext->getTotalLength())),
+   diskWriterFactory_(new DefaultDiskWriterFactory()),
+   endGame_(false),
+   endGamePieceNum_(END_GAME_PIECE_NUM),
+   option_(option),
+   pieceStatMan_(new PieceStatMan(downloadContext->getNumPieces(), true)),
+   pieceSelector_(new RarestPieceSelector(pieceStatMan_))
 {}
 
-DefaultPieceStorage::~DefaultPieceStorage() {
+DefaultPieceStorage::~DefaultPieceStorage()
+{
   delete bitfieldMan_;
 }
 
@@ -130,10 +131,8 @@ void DefaultPieceStorage::addUsedPiece(const SharedHandle<Piece>& piece)
     std::lower_bound(usedPieces_.begin(), usedPieces_.end(), piece,
                      DerefLess<SharedHandle<Piece> >());
   usedPieces_.insert(i, piece);
-  if(logger_->debug()) {
-    logger_->debug("usedPieces_.size()=%lu",
-                   static_cast<unsigned long>(usedPieces_.size()));
-  }
+  A2_LOG_DEBUG(fmt("usedPieces_.size()=%lu",
+                   static_cast<unsigned long>(usedPieces_.size())));
 }
 
 SharedHandle<Piece> DefaultPieceStorage::findUsedPiece(size_t index) const
@@ -428,12 +427,12 @@ void DefaultPieceStorage::completePiece(const SharedHandle<Piece>& piece)
   if(downloadFinished()) {
     downloadContext_->resetDownloadStopTime();
     if(isSelectiveDownloadingMode()) {
-      logger_->notice(MSG_SELECTIVE_DOWNLOAD_COMPLETED);
+      A2_LOG_NOTICE(MSG_SELECTIVE_DOWNLOAD_COMPLETED);
       // following line was commented out in order to stop sending request
       // message after user-specified files were downloaded.
       //finishSelectiveDownloadingMode();
     } else {
-      logger_->info(MSG_DOWNLOAD_COMPLETED);
+      A2_LOG_INFO(MSG_DOWNLOAD_COMPLETED);
     }
 #ifdef ENABLE_BITTORRENT
     if(downloadContext_->hasAttribute(bittorrent::BITTORRENT)) {
@@ -561,9 +560,7 @@ bool DefaultPieceStorage::allDownloadFinished()
 void DefaultPieceStorage::initStorage()
 {
   if(downloadContext_->getFileEntries().size() == 1) {
-    if(logger_->debug()) {
-      logger_->debug("Instantiating DirectDiskAdaptor");
-    }
+    A2_LOG_DEBUG("Instantiating DirectDiskAdaptor");
     DirectDiskAdaptorHandle directDiskAdaptor(new DirectDiskAdaptor());
     directDiskAdaptor->setTotalLength(downloadContext_->getTotalLength());
     directDiskAdaptor->setFileEntries
@@ -579,9 +576,7 @@ void DefaultPieceStorage::initStorage()
     directDiskAdaptor->setDiskWriter(writer);
     diskAdaptor_ = directDiskAdaptor;
   } else {
-    if(logger_->debug()) {
-      logger_->debug("Instantiating MultiDiskAdaptor");
-    }
+    A2_LOG_DEBUG("Instantiating MultiDiskAdaptor");
     MultiDiskAdaptorHandle multiDiskAdaptor(new MultiDiskAdaptor());
     multiDiskAdaptor->setFileEntries(downloadContext_->getFileEntries().begin(),
                                      downloadContext_->getFileEntries().end());
@@ -671,10 +666,8 @@ void DefaultPieceStorage::removeAdvertisedPiece(time_t elapsed)
   std::deque<HaveEntry>::iterator itr =
     std::find_if(haves_.begin(), haves_.end(), FindElapsedHave(elapsed));
   if(itr != haves_.end()) {
-    if(logger_->debug()) {
-      logger_->debug(MSG_REMOVED_HAVE_ENTRY,
-                     static_cast<unsigned long>(haves_.end()-itr));
-    }
+    A2_LOG_DEBUG(fmt(MSG_REMOVED_HAVE_ENTRY,
+                     static_cast<unsigned long>(haves_.end()-itr)));
     haves_.erase(itr, haves_.end());
   }
 }
diff --git a/src/DefaultPieceStorage.h b/src/DefaultPieceStorage.h
index bde118a3..0fb22ff3 100644
--- a/src/DefaultPieceStorage.h
+++ b/src/DefaultPieceStorage.h
@@ -43,7 +43,6 @@ namespace aria2 {
 
 class DownloadContext;
 class BitfieldMan;
-class Logger;
 class Option;
 class DiskWriterFactory;
 class FileEntry;
@@ -80,7 +79,6 @@ private:
 
   bool endGame_;
   size_t endGamePieceNum_;
-  Logger* logger_;
   const Option* option_;
   std::deque<HaveEntry> haves_;
 
diff --git a/src/DiskAdaptor.cc b/src/DiskAdaptor.cc
index 8d307869..12b42f66 100644
--- a/src/DiskAdaptor.cc
+++ b/src/DiskAdaptor.cc
@@ -34,14 +34,12 @@
 /* copyright --> */
 #include "DiskAdaptor.h"
 #include "FileEntry.h"
-#include "LogFactory.h"
-#include "Logger.h"
 
 namespace aria2 {
 
-DiskAdaptor::DiskAdaptor():
-  fallocate_(false),
-  logger_(LogFactory::getInstance()) {}
+DiskAdaptor::DiskAdaptor()
+  : fallocate_(false)
+{}
 
 DiskAdaptor::~DiskAdaptor() {}
 
diff --git a/src/DiskAdaptor.h b/src/DiskAdaptor.h
index fa215707..91bc13b0 100644
--- a/src/DiskAdaptor.h
+++ b/src/DiskAdaptor.h
@@ -45,7 +45,6 @@
 namespace aria2 {
 
 class FileEntry;
-class Logger;
 class FileAllocationIterator;
 
 class DiskAdaptor:public BinaryStream {
@@ -53,13 +52,6 @@ private:
   std::vector<SharedHandle<FileEntry> > fileEntries_;
 
   bool fallocate_;
-
-  Logger* logger_;
-protected:
-  Logger* getLogger() const
-  {
-    return logger_;
-  }
 public:
   DiskAdaptor();
   virtual ~DiskAdaptor();
diff --git a/src/DownloadCommand.cc b/src/DownloadCommand.cc
index b47f6d28..837ee004 100644
--- a/src/DownloadCommand.cc
+++ b/src/DownloadCommand.cc
@@ -45,6 +45,7 @@
 #include "SegmentMan.h"
 #include "Segment.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "ChecksumCheckIntegrityEntry.h"
 #include "PieceStorage.h"
 #include "CheckIntegrityCommand.h"
@@ -56,6 +57,7 @@
 #include "message.h"
 #include "prefs.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "RequestGroupMan.h"
 #include "wallclock.h"
 #include "SinkStreamFilter.h"
@@ -197,10 +199,8 @@ bool DownloadCommand::executeInternal() {
       // If segment->getLength() == 0, the server doesn't provide
       // content length, but the client detected that download
       // completed.
-      if(getLogger()->info()) {
-        getLogger()->info(MSG_SEGMENT_DOWNLOAD_COMPLETED,
-                          util::itos(getCuid()).c_str());
-      }
+      A2_LOG_INFO(fmt(MSG_SEGMENT_DOWNLOAD_COMPLETED,
+                      util::itos(getCuid()).c_str()));
 #ifdef ENABLE_MESSAGE_DIGEST
 
       {
@@ -213,11 +213,8 @@ bool DownloadCommand::executeInternal() {
               !getDownloadContext()->hasAttribute(bittorrent::BITTORRENT)) &&
 #endif // ENABLE_BITTORRENT
              segment->isHashCalculated()) {
-            if(getLogger()->debug()) {
-              getLogger()->debug
-                ("Hash is available! index=%lu",
-                 static_cast<unsigned long>(segment->getIndex()));
-            }
+            A2_LOG_DEBUG(fmt("Hash is available! index=%lu",
+                             static_cast<unsigned long>(segment->getIndex())));
             validatePieceHash
               (segment, expectedPieceHash, segment->getHashString());
           } else {
@@ -340,14 +337,14 @@ void DownloadCommand::validatePieceHash(const SharedHandle<Segment>& segment,
                                         const std::string& actualPieceHash)
 {
   if(actualPieceHash == expectedPieceHash) {
-    getLogger()->info(MSG_GOOD_CHUNK_CHECKSUM, actualPieceHash.c_str());
+    A2_LOG_INFO(fmt(MSG_GOOD_CHUNK_CHECKSUM, actualPieceHash.c_str()));
     getSegmentMan()->completeSegment(getCuid(), segment);
   } else {
-    getLogger()->info(EX_INVALID_CHUNK_CHECKSUM,
-                      static_cast<unsigned long>(segment->getIndex()),
-                      util::itos(segment->getPosition(), true).c_str(),
-                      expectedPieceHash.c_str(),
-                      actualPieceHash.c_str());
+    A2_LOG_INFO(fmt(EX_INVALID_CHUNK_CHECKSUM,
+                    static_cast<unsigned long>(segment->getIndex()),
+                    util::itos(segment->getPosition(), true).c_str(),
+                    expectedPieceHash.c_str(),
+                    actualPieceHash.c_str()));
     segment->clear();
     getSegmentMan()->cancelSegment(getCuid());
     throw DL_RETRY_EX
diff --git a/src/DownloadEngine.cc b/src/DownloadEngine.cc
index a6b33732..ec23ce2a 100644
--- a/src/DownloadEngine.cc
+++ b/src/DownloadEngine.cc
@@ -64,6 +64,7 @@
 #include "CheckIntegrityEntry.h"
 #include "BtProgressInfoFile.h"
 #include "DownloadContext.h"
+#include "fmt.h"
 #ifdef ENABLE_BITTORRENT
 # include "BtRegistry.h"
 #endif // ENABLE_BITTORRENT
@@ -85,17 +86,16 @@ volatile sig_atomic_t globalHaltRequested = 0;
 
 } // namespace global
 
-DownloadEngine::DownloadEngine(const SharedHandle<EventPoll>& eventPoll):
-  eventPoll_(eventPoll),
-  logger_(LogFactory::getInstance()),
-  haltRequested_(false),
-  noWait_(false),
-  refreshInterval_(DEFAULT_REFRESH_INTERVAL),
-  cookieStorage_(new CookieStorage()),
+DownloadEngine::DownloadEngine(const SharedHandle<EventPoll>& eventPoll)
+  : eventPoll_(eventPoll),
+    haltRequested_(false),
+    noWait_(false),
+    refreshInterval_(DEFAULT_REFRESH_INTERVAL),
+    cookieStorage_(new CookieStorage()),
 #ifdef ENABLE_BITTORRENT
-  btRegistry_(new BtRegistry()),
+    btRegistry_(new BtRegistry()),
 #endif // ENABLE_BITTORRENT
-  dnsCache_(new DNSCache())
+    dnsCache_(new DNSCache())
 {
   unsigned char sessionId[20];
   util::generateRandomKey(sessionId);
@@ -217,14 +217,14 @@ void DownloadEngine::afterEachIteration()
 {
   requestGroupMan_->calculateStat();
   if(global::globalHaltRequested == 1) {
-    logger_->notice(_("Shutdown sequence commencing..."
-                      " Press Ctrl-C again for emergency shutdown."));
+    A2_LOG_NOTICE(_("Shutdown sequence commencing..."
+                    " Press Ctrl-C again for emergency shutdown."));
     requestHalt();
     global::globalHaltRequested = 2;
     setNoWait(true);
     setRefreshInterval(0);
   } else if(global::globalHaltRequested == 3) {
-    logger_->notice(_("Emergency shutdown sequence commencing..."));
+    A2_LOG_NOTICE(_("Emergency shutdown sequence commencing..."));
     requestForceHalt();
     global::globalHaltRequested = 4;
     setNoWait(true);
@@ -276,15 +276,13 @@ void DownloadEngine::addRoutineCommand(Command* command)
 void DownloadEngine::poolSocket(const std::string& key,
                                 const SocketPoolEntry& entry)
 {
-  logger_->info("Pool socket for %s", key.c_str());
+  A2_LOG_INFO(fmt("Pool socket for %s", key.c_str()));
   std::multimap<std::string, SocketPoolEntry>::value_type p(key, entry);
   socketPool_.insert(p);
 
   if(lastSocketPoolScan_.difference(global::wallclock) >= 60) {
     std::multimap<std::string, SocketPoolEntry> newPool;
-    if(logger_->debug()) {
-      logger_->debug("Scaning SocketPool and erasing timed out entry.");
-    }
+    A2_LOG_DEBUG("Scaning SocketPool and erasing timed out entry.");
     lastSocketPoolScan_ = global::wallclock;
     for(std::multimap<std::string, SocketPoolEntry>::iterator i =
           socketPool_.begin(), eoi = socketPool_.end(); i != eoi; ++i) {
@@ -292,11 +290,9 @@ void DownloadEngine::poolSocket(const std::string& key,
         newPool.insert(*i);
       }
     }
-    if(logger_->debug()) {
-      logger_->debug
-        ("%lu entries removed.",
-         static_cast<unsigned long>(socketPool_.size()-newPool.size()));
-    }
+    A2_LOG_DEBUG(fmt("%lu entries removed.",
+                     static_cast<unsigned long>
+                     (socketPool_.size()-newPool.size())));
     socketPool_ = newPool;
   }
 }
@@ -402,7 +398,7 @@ DownloadEngine::findSocketPoolEntry(const std::string& key)
     // We assume that if socket is readable it means peer shutdowns
     // connection and the socket will receive EOF. So skip it.
     if(!e.isTimeout() && !e.getSocket()->isReadable(0)) {
-      logger_->info("Found socket for %s", key.c_str());
+      A2_LOG_INFO(fmt("Found socket for %s", key.c_str()));
       return i;
     }
   }
diff --git a/src/DownloadEngine.h b/src/DownloadEngine.h
index ded45806..675920cb 100644
--- a/src/DownloadEngine.h
+++ b/src/DownloadEngine.h
@@ -56,7 +56,6 @@
 
 namespace aria2 {
 
-class Logger;
 class Option;
 class RequestGroupMan;
 class StatCalc;
@@ -78,8 +77,6 @@ private:
 
   SharedHandle<EventPoll> eventPoll_;
 
-  Logger* logger_;
-  
   SharedHandle<StatCalc> statCalc_;
 
   bool haltRequested_;
diff --git a/src/DownloadEngineFactory.cc b/src/DownloadEngineFactory.cc
index 0f4b0d18..5b793cad 100644
--- a/src/DownloadEngineFactory.cc
+++ b/src/DownloadEngineFactory.cc
@@ -36,8 +36,6 @@
 
 #include <algorithm>
 
-#include "LogFactory.h"
-#include "Logger.h"
 #include "Option.h"
 #include "RequestGroup.h"
 #include "DownloadEngine.h"
@@ -80,8 +78,7 @@
 
 namespace aria2 {
 
-DownloadEngineFactory::DownloadEngineFactory():
-  logger_(LogFactory::getInstance()) {}
+DownloadEngineFactory::DownloadEngineFactory() {}
 
 DownloadEngineHandle
 DownloadEngineFactory::newDownloadEngine
diff --git a/src/DownloadEngineFactory.h b/src/DownloadEngineFactory.h
index 23311842..1d42a252 100644
--- a/src/DownloadEngineFactory.h
+++ b/src/DownloadEngineFactory.h
@@ -43,14 +43,11 @@
 
 namespace aria2 {
 
-class Logger;
 class Option;
 class RequestGroup;
 class DownloadEngine;
 
 class DownloadEngineFactory {
-private:
-  Logger* logger_;
 public:
   DownloadEngineFactory();
 
diff --git a/src/DownloadHandler.cc b/src/DownloadHandler.cc
index b708e2c1..db2c02fe 100644
--- a/src/DownloadHandler.cc
+++ b/src/DownloadHandler.cc
@@ -33,15 +33,13 @@
  */
 /* copyright --> */
 #include "DownloadHandler.h"
-#include "LogFactory.h"
-#include "Logger.h"
 #include "RequestGroup.h"
 #include "RequestGroupCriteria.h"
 #include "DownloadContext.h"
 
 namespace aria2 {
 
-DownloadHandler::DownloadHandler():logger_(LogFactory::getInstance()) {}
+DownloadHandler::DownloadHandler() {}
 
 DownloadHandler::~DownloadHandler() {}
 
diff --git a/src/DownloadHandler.h b/src/DownloadHandler.h
index 15daba79..a042eec7 100644
--- a/src/DownloadHandler.h
+++ b/src/DownloadHandler.h
@@ -44,20 +44,12 @@
 namespace aria2 {
 
 class RequestGroup;
-class Logger;
 class RequestGroupCriteria;
 
 class DownloadHandler
 {
 private:
   SharedHandle<RequestGroupCriteria> criteria_;
-
-  Logger* logger_;
-protected:
-  Logger* getLogger() const
-  {
-    return logger_;
-  }
 public:
   DownloadHandler();
 
diff --git a/src/EpollEventPoll.cc b/src/EpollEventPoll.cc
index d7077fdb..e82b051c 100644
--- a/src/EpollEventPoll.cc
+++ b/src/EpollEventPoll.cc
@@ -44,6 +44,7 @@
 #include "Logger.h"
 #include "util.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -80,10 +81,9 @@ struct epoll_event EpollEventPoll::KSocketEntry::getEvents()
   return epEvent;
 }
 
-EpollEventPoll::EpollEventPoll():
-  epEventsSize_(EPOLL_EVENTS_MAX),
-  epEvents_(new struct epoll_event[epEventsSize_]),
-  logger_(LogFactory::getInstance())
+EpollEventPoll::EpollEventPoll()
+  : epEventsSize_(EPOLL_EVENTS_MAX),
+    epEvents_(new struct epoll_event[epEventsSize_])
 {
   epfd_ = epoll_create(EPOLL_EVENTS_MAX);
 }
@@ -95,9 +95,10 @@ EpollEventPoll::~EpollEventPoll()
     while((r = close(epfd_)) == -1 && errno == EINTR);
     int errNum = errno;
     if(r == -1) {
-      logger_->error("Error occurred while closing epoll file descriptor"
-                     " %d: %s",
-                     epfd_, util::safeStrerror(errNum).c_str());
+      A2_LOG_ERROR(fmt("Error occurred while closing epoll file descriptor"
+                       " %d: %s",
+                       epfd_,
+                       util::safeStrerror(errNum).c_str()));
     }
   }
   delete [] epEvents_;
@@ -201,10 +202,9 @@ bool EpollEventPoll::addEvents(sock_t socket,
     errNum = errno;
   }
   if(r == -1) {
-    if(logger_->debug()) {
-      logger_->debug("Failed to add socket event %d:%s",
-                     socket, util::safeStrerror(errNum).c_str());
-    }
+    A2_LOG_DEBUG(fmt("Failed to add socket event %d:%s",
+                     socket,
+                     util::safeStrerror(errNum).c_str()));
     return false;
   } else {
     return true;
@@ -253,25 +253,19 @@ bool EpollEventPoll::deleteEvents(sock_t socket,
       r = epoll_ctl(epfd_, EPOLL_CTL_MOD, (*i)->getSocket(), &epEvent);
       errNum = r;
       if(r == -1) {
-        if(logger_->debug()) {
-          logger_->debug("Failed to delete socket event, but may be ignored:%s",
-                         util::safeStrerror(errNum).c_str());
-        }
+        A2_LOG_DEBUG(fmt("Failed to delete socket event, but may be ignored:%s",
+                         util::safeStrerror(errNum).c_str()));
       }
     }
     if(r == -1) {
-      if(logger_->debug()) {
-        logger_->debug("Failed to delete socket event:%s",
-                       util::safeStrerror(errNum).c_str());
-      }
+      A2_LOG_DEBUG(fmt("Failed to delete socket event:%s",
+                       util::safeStrerror(errNum).c_str()));
       return false;
     } else {
       return true;
     }
   } else {
-    if(logger_->debug()) {
-      logger_->debug("Socket %d is not found in SocketEntries.", socket);
-    }
+    A2_LOG_DEBUG(fmt("Socket %d is not found in SocketEntries.", socket));
     return false;
   }
 }
diff --git a/src/EpollEventPoll.h b/src/EpollEventPoll.h
index 144319b9..8b6ba167 100644
--- a/src/EpollEventPoll.h
+++ b/src/EpollEventPoll.h
@@ -48,8 +48,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class EpollEventPoll : public EventPoll {
 private:
   class KSocketEntry;
@@ -84,8 +82,6 @@ private:
 
   static const size_t EPOLL_EVENTS_MAX = 1024;
 
-  Logger* logger_;
-
   bool addEvents(sock_t socket, const KEvent& event);
 
   bool deleteEvents(sock_t socket, const KEvent& event);
diff --git a/src/FeedbackURISelector.cc b/src/FeedbackURISelector.cc
index 6ee7d9d2..cb9ad199 100644
--- a/src/FeedbackURISelector.cc
+++ b/src/FeedbackURISelector.cc
@@ -45,13 +45,14 @@
 #include "LogFactory.h"
 #include "a2algo.h"
 #include "uri.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 FeedbackURISelector::FeedbackURISelector
-(const SharedHandle<ServerStatMan>& serverStatMan):
-  serverStatMan_(serverStatMan),
-  logger_(LogFactory::getInstance()) {}
+(const SharedHandle<ServerStatMan>& serverStatMan)
+  : serverStatMan_(serverStatMan)
+{}
 
 FeedbackURISelector::~FeedbackURISelector() {}
 
@@ -71,12 +72,12 @@ std::string FeedbackURISelector::select
 (FileEntry* fileEntry,
  const std::vector<std::pair<size_t, std::string> >& usedHosts)
 {
-  if(logger_->debug()) {
+  if(A2_LOG_DEBUG_ENABLED) {
     for(std::vector<std::pair<size_t, std::string> >::const_iterator i =
           usedHosts.begin(), eoi = usedHosts.end(); i != eoi; ++i) {
-      logger_->debug("UsedHost=%lu, %s",
-                     static_cast<unsigned long>((*i).first),
-                     (*i).second.c_str());
+      A2_LOG_DEBUG(fmt("UsedHost=%lu, %s",
+                       static_cast<unsigned long>((*i).first),
+                       (*i).second.c_str()));
     }
   }
   if(fileEntry->getRemainingUris().empty()) {
@@ -86,18 +87,14 @@ std::string FeedbackURISelector::select
   // it again without usedHosts.
   std::string uri = selectFaster(fileEntry->getRemainingUris(), usedHosts);
   if(uri.empty()) {
-    if(logger_->debug()) {
-      logger_->debug("No URI returned from selectFaster()");
-    }
+    A2_LOG_DEBUG("No URI returned from selectFaster()");
     uri = selectRarer(fileEntry->getRemainingUris(), usedHosts);
   } 
   if(!uri.empty()) {
     std::deque<std::string>& uris = fileEntry->getRemainingUris();
     uris.erase(std::find(uris.begin(), uris.end(), uri));
   }
-  if(logger_->debug()) {
-    logger_->debug("FeedbackURISelector selected %s", uri.c_str());
-  }
+  A2_LOG_DEBUG(fmt("FeedbackURISelector selected %s", uri.c_str()));
   return uri;
 }
 
@@ -116,9 +113,7 @@ std::string FeedbackURISelector::selectRarer
     SharedHandle<ServerStat> ss =
       serverStatMan_->find(us.host, us.protocol);
     if(ss && ss->isError()) {
-      if(logger_->debug()) {
-        logger_->debug("Error not considered: %s", (*i).c_str());
-      }
+      A2_LOG_DEBUG(fmt("Error not considered: %s", (*i).c_str()));
       continue;
     }
     cands.push_back(std::make_pair(us.host, *i));
@@ -154,9 +149,7 @@ std::string FeedbackURISelector::selectFaster
     }
     if(findSecond(usedHosts.begin(), usedHosts.end(), us.host) !=
        usedHosts.end()) {
-      if(logger_->debug()) {
-        logger_->debug("%s is in usedHosts, not considered", (*i).c_str());
-      }
+      A2_LOG_DEBUG(fmt("%s is in usedHosts, not considered", (*i).c_str()));
       continue;
     }
     SharedHandle<ServerStat> ss =
@@ -175,15 +168,11 @@ std::string FeedbackURISelector::selectFaster
     if(normCands.empty()) {
       return A2STR::NIL;
     } else {
-      if(logger_->debug()) {
-        logger_->debug("Selected from normCands");
-      }
+      A2_LOG_DEBUG("Selected from normCands");
       return normCands.front();
     }
   } else {
-    if(logger_->debug()) {
-      logger_->debug("Selected from fastCands");
-    }
+    A2_LOG_DEBUG("Selected from fastCands");
     std::sort(fastCands.begin(), fastCands.end(), ServerStatFaster());
     return fastCands.front().second;
   }
diff --git a/src/FeedbackURISelector.h b/src/FeedbackURISelector.h
index cfaddc87..6f5ced64 100644
--- a/src/FeedbackURISelector.h
+++ b/src/FeedbackURISelector.h
@@ -40,14 +40,11 @@
 namespace aria2 {
 
 class ServerStatMan;
-class Logger;
 
 class FeedbackURISelector:public URISelector {
 private:
   SharedHandle<ServerStatMan> serverStatMan_;
 
-  Logger* logger_;
-
   std::string selectRarer
   (const std::deque<std::string>& uris,
    const std::vector<std::pair<size_t, std::string> >& usedHosts);
diff --git a/src/FileAllocationCommand.cc b/src/FileAllocationCommand.cc
index a0b9a296..3373d784 100644
--- a/src/FileAllocationCommand.cc
+++ b/src/FileAllocationCommand.cc
@@ -38,6 +38,7 @@
 #include "DownloadEngine.h"
 #include "RequestGroup.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "message.h"
 #include "prefs.h"
 #include "util.h"
@@ -47,6 +48,7 @@
 #include "RecoverableException.h"
 #include "wallclock.h"
 #include "RequestGroupMan.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -66,12 +68,10 @@ bool FileAllocationCommand::executeInternal()
   }
   fileAllocationEntry_->allocateChunk();
   if(fileAllocationEntry_->finished()) {
-    if(getLogger()->debug()) {
-      getLogger()->debug
-        (MSG_ALLOCATION_COMPLETED,
-         static_cast<long int>(timer_.difference(global::wallclock)),
-         util::itos(getRequestGroup()->getTotalLength(), true).c_str());
-    }
+    A2_LOG_DEBUG
+      (fmt(MSG_ALLOCATION_COMPLETED,
+           static_cast<long int>(timer_.difference(global::wallclock)),
+           util::itos(getRequestGroup()->getTotalLength(), true).c_str()));
     getDownloadEngine()->getFileAllocationMan()->dropPickedEntry();
     
     std::vector<Command*>* commands = new std::vector<Command*>();
@@ -90,11 +90,13 @@ bool FileAllocationCommand::executeInternal()
 bool FileAllocationCommand::handleException(Exception& e)
 {
   getDownloadEngine()->getFileAllocationMan()->dropPickedEntry();
-  getLogger()->error
-    (MSG_FILE_ALLOCATION_FAILURE, e, util::itos(getCuid()).c_str());
-  getLogger()->error
-    (MSG_DOWNLOAD_NOT_COMPLETE, util::itos(getCuid()).c_str(),
-     getRequestGroup()->getDownloadContext()->getBasePath().c_str());
+  A2_LOG_ERROR_EX(fmt(MSG_FILE_ALLOCATION_FAILURE,
+                      util::itos(getCuid()).c_str()),
+                  e);
+  A2_LOG_ERROR
+    (fmt(MSG_DOWNLOAD_NOT_COMPLETE,
+         util::itos(getCuid()).c_str(),
+         getRequestGroup()->getDownloadContext()->getBasePath().c_str()));
   return true;
 }
 
diff --git a/src/FileAllocationDispatcherCommand.cc b/src/FileAllocationDispatcherCommand.cc
index 46c2f7fd..58a82061 100644
--- a/src/FileAllocationDispatcherCommand.cc
+++ b/src/FileAllocationDispatcherCommand.cc
@@ -37,7 +37,9 @@
 #include "FileAllocationCommand.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -51,10 +53,7 @@ Command* FileAllocationDispatcherCommand::createCommand
 (const SharedHandle<FileAllocationEntry>& entry)
 {
   cuid_t newCUID = getDownloadEngine()->newCUID();
-  if(getLogger()->info()) {
-    getLogger()->info(MSG_FILE_ALLOCATION_DISPATCH,
-                      util::itos(newCUID).c_str());
-  }
+  A2_LOG_INFO(fmt(MSG_FILE_ALLOCATION_DISPATCH, util::itos(newCUID).c_str()));
   FileAllocationCommand* command =
     new FileAllocationCommand(newCUID, entry->getRequestGroup(),
                               getDownloadEngine(), entry);
diff --git a/src/FileEntry.cc b/src/FileEntry.cc
index c8664941..59c74fc5 100644
--- a/src/FileEntry.cc
+++ b/src/FileEntry.cc
@@ -39,31 +39,38 @@
 
 #include "util.h"
 #include "URISelector.h"
+#include "Logger.h"
 #include "LogFactory.h"
 #include "wallclock.h"
 #include "a2algo.h"
 #include "uri.h"
 #include "PeerStat.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-FileEntry::FileEntry(const std::string& path,
-                     uint64_t length,
-                     off_t offset,
-                     const std::vector<std::string>& uris):
-  path_(path), uris_(uris.begin(), uris.end()), length_(length),
-  offset_(offset),
-  requested_(true),
-  uniqueProtocol_(false),
-  maxConnectionPerServer_(1),
-  lastFasterReplace_(0),
-  logger_(LogFactory::getInstance()) {}
-
-FileEntry::FileEntry():
-  length_(0), offset_(0), requested_(false),
-  uniqueProtocol_(false),
-  maxConnectionPerServer_(1),
-  logger_(LogFactory::getInstance()) {}
+FileEntry::FileEntry
+(const std::string& path,
+ uint64_t length,
+ off_t offset,
+ const std::vector<std::string>& uris)
+  : path_(path),
+    uris_(uris.begin(), uris.end()),
+    length_(length),
+    offset_(offset),
+    requested_(true),
+    uniqueProtocol_(false),
+    maxConnectionPerServer_(1),
+    lastFasterReplace_(0)
+{}
+
+FileEntry::FileEntry()
+ : length_(0),
+   offset_(0),
+   requested_(false),
+   uniqueProtocol_(false),
+   maxConnectionPerServer_(1)
+{}
 
 FileEntry::~FileEntry() {}
 
@@ -172,9 +179,7 @@ FileEntry::getRequest
     req = requestPool_.front();
     requestPool_.pop_front();
     inFlightRequests_.push_back(req);
-    if(logger_->debug()) {
-      logger_->debug("Picked up from pool: %s", req->getUri().c_str());
-    }
+    A2_LOG_DEBUG(fmt("Picked up from pool: %s", req->getUri().c_str()));
   }
   return req;
 }
@@ -273,11 +278,9 @@ void FileEntry::removeURIWhoseHostnameIs(const std::string& hostname)
       newURIs.push_back(*itr);
     }
   }
-  if(logger_->debug()) {
-    logger_->debug("Removed %lu duplicate hostname URIs for path=%s",
+  A2_LOG_DEBUG(fmt("Removed %lu duplicate hostname URIs for path=%s",
                    static_cast<unsigned long>(uris_.size()-newURIs.size()),
-                   getPath().c_str());
-  }
+                   getPath().c_str()));
   uris_.swap(newURIs);
 }
 
@@ -317,10 +320,10 @@ void FileEntry::extractURIResult
 
 void FileEntry::reuseUri(const std::vector<std::string>& ignore)
 {
-  if(logger_->debug()) {
+  if(A2_LOG_DEBUG_ENABLED) {
     for(std::vector<std::string>::const_iterator i = ignore.begin(),
           eoi = ignore.end(); i != eoi; ++i) {
-      logger_->debug("ignore host=%s", (*i).c_str());
+      A2_LOG_DEBUG(fmt("ignore host=%s", (*i).c_str()));
     }
   }
   std::deque<std::string> uris = spentUris_;
@@ -333,10 +336,10 @@ void FileEntry::reuseUri(const std::vector<std::string>& ignore)
   std::sort(errorUris.begin(), errorUris.end());
   errorUris.erase(std::unique(errorUris.begin(), errorUris.end()),
                   errorUris.end());
-  if(logger_->debug()) {
+  if(A2_LOG_DEBUG_ENABLED) {
     for(std::vector<std::string>::const_iterator i = errorUris.begin(),
           eoi = errorUris.end(); i != eoi; ++i) {
-      logger_->debug("error URI=%s", (*i).c_str());
+      A2_LOG_DEBUG(fmt("error URI=%s", (*i).c_str()));
     }
   }
   std::vector<std::string> reusableURIs;
@@ -357,11 +360,12 @@ void FileEntry::reuseUri(const std::vector<std::string>& ignore)
   }
   reusableURIs.erase(insertionPoint, reusableURIs.end());
   size_t ininum = reusableURIs.size();
-  if(logger_->debug()) {
-    logger_->debug("Found %u reusable URIs", static_cast<unsigned int>(ininum));
+  if(A2_LOG_DEBUG_ENABLED) {
+    A2_LOG_DEBUG(fmt("Found %u reusable URIs",
+                     static_cast<unsigned int>(ininum)));
     for(std::vector<std::string>::const_iterator i = reusableURIs.begin(),
           eoi = reusableURIs.end(); i != eoi; ++i) {
-      logger_->debug("URI=%s", (*i).c_str());
+      A2_LOG_DEBUG(fmt("URI=%s", (*i).c_str()));
     }
   }
   uris_.insert(uris_.end(), reusableURIs.begin(), reusableURIs.end());
diff --git a/src/FileEntry.h b/src/FileEntry.h
index 0d661af3..3fa6444d 100644
--- a/src/FileEntry.h
+++ b/src/FileEntry.h
@@ -54,8 +54,6 @@ namespace aria2 {
 
 class URISelector;
 
-class Logger;
-
 class FileEntry {
 private:
   std::string path_;
@@ -74,7 +72,6 @@ private:
   size_t maxConnectionPerServer_;
   std::string originalName_;
   Timer lastFasterReplace_;
-  Logger* logger_;
 
   void storePool(const SharedHandle<Request>& request);
 public:
diff --git a/src/FillRequestGroupCommand.cc b/src/FillRequestGroupCommand.cc
index 191b153e..5942489c 100644
--- a/src/FillRequestGroupCommand.cc
+++ b/src/FillRequestGroupCommand.cc
@@ -39,7 +39,9 @@
 #include "RecoverableException.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "DownloadContext.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -68,7 +70,7 @@ bool FillRequestGroupCommand::execute()
         rgman->clearQueueCheck();
         rgman->fillRequestGroupFromReserver(e_);
       } catch(RecoverableException& ex) {
-        getLogger()->error(EX_EXCEPTION_CAUGHT, ex);
+        A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, ex);
         // Re-request queue check to fulfill the requests of all
         // downloads, some might come after this exception.
         rgman->requestQueueCheck();
diff --git a/src/FtpConnection.cc b/src/FtpConnection.cc
index f690ae6b..b8d0f76a 100644
--- a/src/FtpConnection.cc
+++ b/src/FtpConnection.cc
@@ -53,8 +53,10 @@
 #include "Socket.h"
 #include "A2STR.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "AuthConfig.h"
 #include "a2functional.h"
+#include "util.h"
 
 namespace aria2 {
 
@@ -62,15 +64,20 @@ const std::string FtpConnection::A("A");
 
 const std::string FtpConnection::I("I");
 
-FtpConnection::FtpConnection(cuid_t cuid, const SocketHandle& socket,
-                             const SharedHandle<Request>& req,
-                             const SharedHandle<AuthConfig>& authConfig,
-                             const Option* op):
-  cuid_(cuid), socket_(socket), req_(req),
-  authConfig_(authConfig), option_(op),
-  logger_(LogFactory::getInstance()),
-  socketBuffer_(socket),
-  baseWorkingDir_("/") {}
+FtpConnection::FtpConnection
+(cuid_t cuid,
+ const SocketHandle& socket,
+ const SharedHandle<Request>& req,
+ const SharedHandle<AuthConfig>& authConfig,
+ const Option* op)
+  : cuid_(cuid),
+    socket_(socket),
+    req_(req),
+    authConfig_(authConfig),
+    option_(op),
+    socketBuffer_(socket),
+    baseWorkingDir_("/")
+{}
 
 FtpConnection::~FtpConnection() {}
 
@@ -80,10 +87,8 @@ bool FtpConnection::sendUser()
     std::string request = "USER ";
     request += authConfig_->getUser();
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(),"USER ********");
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), "USER ********"));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -96,10 +101,8 @@ bool FtpConnection::sendPass()
     std::string request = "PASS ";
     request += authConfig_->getPassword();
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(),"PASS ********");
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), "PASS ********"));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -118,10 +121,8 @@ bool FtpConnection::sendType()
     std::string request = "TYPE ";
     request += type;
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(),request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(),request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -132,10 +133,8 @@ bool FtpConnection::sendPwd()
 {
   if(socketBuffer_.sendBufferIsEmpty()) {
     std::string request = "PWD\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(),request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(),request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -148,10 +147,8 @@ bool FtpConnection::sendCwd(const std::string& dir)
     std::string request = "CWD ";
     request += util::percentDecode(dir);
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(),request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(),request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -164,10 +161,8 @@ bool FtpConnection::sendMdtm()
     std::string request = "MDTM ";
     request += util::percentDecode(req_->getFile());
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -180,10 +175,8 @@ bool FtpConnection::sendSize()
     std::string request = "SIZE ";
     request += util::percentDecode(req_->getFile());
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -194,10 +187,8 @@ bool FtpConnection::sendEpsv()
 {
   if(socketBuffer_.sendBufferIsEmpty()) {
     static const std::string request("EPSV\r\n");
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -208,10 +199,8 @@ bool FtpConnection::sendPasv()
 {
   if(socketBuffer_.sendBufferIsEmpty()) {
     static const std::string request("PASV\r\n");
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -245,10 +234,8 @@ bool FtpConnection::sendEprt(const SharedHandle<SocketCore>& serverSocket)
     request += "|";
     request += util::uitos(addrinfo.second);
     request += "|\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -277,10 +264,8 @@ bool FtpConnection::sendPort(const SharedHandle<SocketCore>& serverSocket)
     request += ",";
     request += util::uitos(addrinfo.second%256);
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -297,10 +282,8 @@ bool FtpConnection::sendRest(const SharedHandle<Segment>& segment)
       request += util::itos(segment->getPositionToWrite());
     }
     request += "\r\n";    
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -313,10 +296,8 @@ bool FtpConnection::sendRetr()
     std::string request = "RETR ";
     request += util::percentDecode(req_->getFile());
     request += "\r\n";
-    if(logger_->info()) {
-      logger_->info(MSG_SENDING_REQUEST,
-                    util::itos(cuid_).c_str(), request.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
+                    util::itos(cuid_).c_str(), request.c_str()));
     socketBuffer_.pushStr(request);
   }
   socketBuffer_.send();
@@ -411,10 +392,9 @@ bool FtpConnection::bulkReceiveResponse
   if((length = findEndOfResponse(status, strbuf_)) != std::string::npos) {
     response.first = status;
     response.second = strbuf_.substr(0, length);
-    if(logger_->info()) {
-      logger_->info(MSG_RECEIVE_RESPONSE,
-                    util::itos(cuid_).c_str(), response.second.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_RECEIVE_RESPONSE,
+                    util::itos(cuid_).c_str(),
+                    response.second.c_str()));
     strbuf_.erase(0, length);
     return true;
   } else {
diff --git a/src/FtpConnection.h b/src/FtpConnection.h
index 51bcf3fe..6a33a33b 100644
--- a/src/FtpConnection.h
+++ b/src/FtpConnection.h
@@ -48,7 +48,6 @@
 namespace aria2 {
 
 class Option;
-class Logger;
 class Segment;
 class Request;
 class SocketCore;
@@ -63,7 +62,6 @@ private:
   SharedHandle<AuthConfig> authConfig_;
 
   const Option* option_;
-  Logger* logger_;
 
   std::string strbuf_;
 
diff --git a/src/FtpFinishDownloadCommand.cc b/src/FtpFinishDownloadCommand.cc
index 64555cd7..d151b204 100644
--- a/src/FtpFinishDownloadCommand.cc
+++ b/src/FtpFinishDownloadCommand.cc
@@ -43,10 +43,12 @@
 #include "FtpConnection.h"
 #include "message.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "DlAbortEx.h"
 #include "SocketCore.h"
 #include "RequestGroup.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "util.h"
 #include "wallclock.h"
 
@@ -90,20 +92,21 @@ bool FtpFinishDownloadCommand::execute()
              getSocket(), options);
         }
       } else {
-        getLogger()->info("CUID#%s - Bad status for transfer complete.",
-                          util::itos(getCuid()).c_str());
+        A2_LOG_INFO(fmt("CUID#%s - Bad status for transfer complete.",
+                        util::itos(getCuid()).c_str()));
       }
     } else if(getCheckPoint().difference(global::wallclock) >= getTimeout()) {
-      getLogger()->info("CUID#%s - Timeout before receiving transfer complete.",
-                        util::itos(getCuid()).c_str());
+      A2_LOG_INFO(fmt("CUID#%s - Timeout before receiving transfer complete.",
+                      util::itos(getCuid()).c_str()));
     } else {
       getDownloadEngine()->addCommand(this);
       return false;
     }
   } catch(RecoverableException& e) {
-    getLogger()->info("CUID#%s - Exception was thrown, but download was"
-                      " finished, so we can ignore the exception.",
-                      e, util::itos(getCuid()).c_str());
+    A2_LOG_INFO_EX(fmt("CUID#%s - Exception was thrown, but download was"
+                       " finished, so we can ignore the exception.",
+                       util::itos(getCuid()).c_str()),
+                   e);
   }
   if(getRequestGroup()->downloadFinished()) {
     return true;
diff --git a/src/FtpInitiateConnectionCommand.cc b/src/FtpInitiateConnectionCommand.cc
index 7538f23e..f7f54c66 100644
--- a/src/FtpInitiateConnectionCommand.cc
+++ b/src/FtpInitiateConnectionCommand.cc
@@ -46,6 +46,7 @@
 #include "FtpTunnelRequestCommand.h"
 #include "DlAbortEx.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "message.h"
 #include "prefs.h"
 #include "HttpConnection.h"
@@ -53,6 +54,7 @@
 #include "util.h"
 #include "AuthConfigFactory.h"
 #include "AuthConfig.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -88,10 +90,8 @@ Command* FtpInitiateConnectionCommand::createNextCommand
          proxyRequest->getHost(), proxyRequest->getPort());
     }
     if(!pooledSocket) {
-      if(getLogger()->info()) {
-        getLogger()->info(MSG_CONNECTING_TO_SERVER,
-                          util::itos(getCuid()).c_str(), addr.c_str(), port);
-      }
+      A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                      util::itos(getCuid()).c_str(), addr.c_str(), port));
       createSocket();
       getSocket()->establishConnection(addr, port);
       
@@ -153,10 +153,8 @@ Command* FtpInitiateConnectionCommand::createNextCommand
        getDownloadEngine()->getAuthConfigFactory()->createAuthConfig
        (getRequest(), getOption().get())->getUser());
     if(!pooledSocket) {
-      if(getLogger()->info()) {
-        getLogger()->info(MSG_CONNECTING_TO_SERVER,
-                          util::itos(getCuid()).c_str(), addr.c_str(), port);
-      }
+      A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                      util::itos(getCuid()).c_str(), addr.c_str(), port));
       createSocket();
       getSocket()->establishConnection(addr, port);
       FtpNegotiationCommand* c =
diff --git a/src/FtpNegotiationCommand.cc b/src/FtpNegotiationCommand.cc
index 57040563..242a8005 100644
--- a/src/FtpNegotiationCommand.cc
+++ b/src/FtpNegotiationCommand.cc
@@ -52,6 +52,7 @@
 #include "util.h"
 #include "Option.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "Segment.h"
 #include "DownloadContext.h"
 #include "DefaultBtProgressInfoFile.h"
@@ -59,6 +60,7 @@
 #include "DownloadFailureException.h"
 #include "Socket.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "DiskAdaptor.h"
 #include "SegmentMan.h"
 #include "AuthConfigFactory.h"
@@ -253,10 +255,8 @@ bool FtpNegotiationCommand::recvPwd()
     throw DL_ABORT_EX(StringFormat(EX_BAD_STATUS, status).str());
   }
   ftp_->setBaseWorkingDir(pwd);
-  if(getLogger()->info()) {
-    getLogger()->info("CUID#%s - base working directory is '%s'",
-                      util::itos(getCuid()).c_str(), pwd.c_str());
-  }
+  A2_LOG_INFO(fmt("CUID#%s - base working directory is '%s'",
+                  util::itos(getCuid()).c_str(), pwd.c_str()));
   sequence_ = SEQ_SEND_CWD_PREP;
   return true;
 }
@@ -332,21 +332,15 @@ bool FtpNegotiationCommand::recvMdtm()
   if(status == 213) {
     if(lastModifiedTime.good()) {
       getRequestGroup()->updateLastModifiedTime(lastModifiedTime);
-      if(getLogger()->debug()) {
-        getLogger()->debug("MDTM result was parsed as: %s",
-                           lastModifiedTime.toHTTPDate().c_str());
-      }
+      A2_LOG_DEBUG(fmt("MDTM result was parsed as: %s",
+                       lastModifiedTime.toHTTPDate().c_str()));
     } else {
-      if(getLogger()->debug()) {
-        getLogger()->debug("MDTM response was returned, but it seems not to be"
-                           " a time value as in specified in RFC3659.");
-      }
+      A2_LOG_DEBUG("MDTM response was returned, but it seems not to be"
+                   " a time value as in specified in RFC3659.");
     }
   } else {
-    if(getLogger()->info()) {
-      getLogger()->info("CUID#%s - MDTM command failed.",
-                        util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO(fmt("CUID#%s - MDTM command failed.",
+                    util::itos(getCuid()).c_str()));
   }
   sequence_ = SEQ_SEND_SIZE;
   return true;  
@@ -403,10 +397,9 @@ bool FtpNegotiationCommand::onFileSizeDetermined(uint64_t totalLength)
       getPieceStorage()->markAllPiecesDone();
       getDownloadContext()->setChecksumVerified(true);
       sequence_ = SEQ_DOWNLOAD_ALREADY_COMPLETED;
-      getLogger()->notice(MSG_DOWNLOAD_ALREADY_COMPLETED,
-                          util::itos(getRequestGroup()->getGID()).c_str(),
-                          getRequestGroup()->getFirstFilePath().c_str());
-
+      A2_LOG_NOTICE(fmt(MSG_DOWNLOAD_ALREADY_COMPLETED,
+                        util::itos(getRequestGroup()->getGID()).c_str(),
+                        getRequestGroup()->getFirstFilePath().c_str()));
       poolConnection();
 
       return false;
@@ -482,10 +475,8 @@ bool FtpNegotiationCommand::recvSize() {
     }
 
   } else {
-    if(getLogger()->info()) {
-      getLogger()->info("CUID#%s - The remote FTP Server doesn't recognize SIZE"
-                        " command. Continue.", util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO(fmt("CUID#%s - The remote FTP Server doesn't recognize SIZE"
+                    " command. Continue.", util::itos(getCuid()).c_str()));
     // Even if one of the other servers waiting in the queue supports SIZE
     // command, resuming and segmented downloading are disabled when the first
     // contacted FTP server doesn't support it.
@@ -648,11 +639,10 @@ bool FtpNegotiationCommand::preparePasvConnect() {
     return true;
   } else {
     // make a data connection to the server.
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_CONNECTING_TO_SERVER, util::itos(getCuid()).c_str(),
-                        dataConnAddr_.first.c_str(),
-                        dataConnAddr_.second);
-    }
+    A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                    util::itos(getCuid()).c_str(),
+                    dataConnAddr_.first.c_str(),
+                    dataConnAddr_.second));
     dataSocket_.reset(new SocketCore());
     dataSocket_->establishConnection(dataConnAddr_.first, dataConnAddr_.second);
     disableReadCheckSocket();
@@ -671,10 +661,9 @@ bool FtpNegotiationCommand::resolveProxy()
   if(proxyAddr_.empty()) {
     return false;
   }
-  if(getLogger()->info()) {
-    getLogger()->info(MSG_CONNECTING_TO_SERVER, util::itos(getCuid()).c_str(),
-                      proxyAddr_.c_str(), proxyReq->getPort());
-  }
+  A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                  util::itos(getCuid()).c_str(),
+                  proxyAddr_.c_str(), proxyReq->getPort()));
   dataSocket_.reset(new SocketCore());                  
   dataSocket_->establishConnection(proxyAddr_, proxyReq->getPort());
   disableReadCheckSocket();
@@ -702,17 +691,13 @@ bool FtpNegotiationCommand::sendTunnelRequest()
             (StringFormat(MSG_ESTABLISHING_CONNECTION_FAILED,
                           error.c_str()).str());
         } else {
-          if(getLogger()->info()) {
-            getLogger()->info(MSG_CONNECT_FAILED_AND_RETRY,
-                              util::itos(getCuid()).c_str(),
-                              proxyAddr_.c_str(), proxyReq->getPort());
-          }
+          A2_LOG_INFO(fmt(MSG_CONNECT_FAILED_AND_RETRY,
+                          util::itos(getCuid()).c_str(),
+                          proxyAddr_.c_str(), proxyReq->getPort()));
           proxyAddr_ = nextProxyAddr;
-          if(getLogger()->info()) {
-            getLogger()->info(MSG_CONNECTING_TO_SERVER,
-                              util::itos(getCuid()).c_str(),
-                              proxyAddr_.c_str(), proxyReq->getPort());
-          }
+          A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                          util::itos(getCuid()).c_str(),
+                          proxyAddr_.c_str(), proxyReq->getPort()));
           dataSocket_->establishConnection(proxyAddr_, proxyReq->getPort());
           return false;
         }
diff --git a/src/HandshakeExtensionMessage.cc b/src/HandshakeExtensionMessage.cc
index c76f629b..925cc32a 100644
--- a/src/HandshakeExtensionMessage.cc
+++ b/src/HandshakeExtensionMessage.cc
@@ -40,6 +40,7 @@
 #include "Logger.h"
 #include "message.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "bencode2.h"
 #include "DownloadContext.h"
 #include "bittorrent_helper.h"
@@ -51,10 +52,10 @@ namespace aria2 {
 
 const std::string HandshakeExtensionMessage::EXTENSION_NAME = "handshake";
 
-HandshakeExtensionMessage::HandshakeExtensionMessage():
-  tcpPort_(0),
-  metadataSize_(0),
-  logger_(LogFactory::getInstance()) {}
+HandshakeExtensionMessage::HandshakeExtensionMessage()
+  : tcpPort_(0),
+    metadataSize_(0)
+{}
 
 HandshakeExtensionMessage::~HandshakeExtensionMessage() {}
 
@@ -175,11 +176,8 @@ HandshakeExtensionMessage::create(const unsigned char* data, size_t length)
                     static_cast<unsigned long>(length)).str());
   }
   HandshakeExtensionMessageHandle msg(new HandshakeExtensionMessage());
-  if(LogFactory::getInstance()->debug()) {
-    LogFactory::getInstance()->debug
-      ("Creating HandshakeExtensionMessage from %s",
-       util::percentEncode(data, length).c_str());
-  }
+  A2_LOG_DEBUG(fmt("Creating HandshakeExtensionMessage from %s",
+                   util::percentEncode(data, length).c_str()));
   SharedHandle<ValueBase> decoded = bencode2::decode(data+1, length-1);
   const Dict* dict = asDict(decoded);
   if(!dict) {
diff --git a/src/HandshakeExtensionMessage.h b/src/HandshakeExtensionMessage.h
index a273c37b..f5650cff 100644
--- a/src/HandshakeExtensionMessage.h
+++ b/src/HandshakeExtensionMessage.h
@@ -44,7 +44,6 @@
 namespace aria2 {
 
 class Peer;
-class Logger;
 class DownloadContext;
 
 class HandshakeExtensionMessage:public ExtensionMessage {
@@ -60,9 +59,6 @@ private:
   SharedHandle<DownloadContext> dctx_;
 
   SharedHandle<Peer> peer_;
-
-  Logger* logger_;
-
 public:
   HandshakeExtensionMessage();
 
diff --git a/src/HttpConnection.cc b/src/HttpConnection.cc
index 7512bca4..36788773 100644
--- a/src/HttpConnection.cc
+++ b/src/HttpConnection.cc
@@ -55,20 +55,22 @@
 #include "AuthConfigFactory.h"
 #include "AuthConfig.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 HttpRequestEntry::HttpRequestEntry
-(const SharedHandle<HttpRequest>& httpRequest):
-  httpRequest_(httpRequest),
-  proc_(new HttpHeaderProcessor()) {}
+(const SharedHandle<HttpRequest>& httpRequest)
+  : httpRequest_(httpRequest),
+    proc_(new HttpHeaderProcessor())
+{}
 
 HttpRequestEntry::~HttpRequestEntry() {}
 
-HttpConnection::HttpConnection(cuid_t cuid, const SocketHandle& socket):
-  cuid_(cuid), socket_(socket),
-  socketBuffer_(socket),
-  logger_(LogFactory::getInstance())
+HttpConnection::HttpConnection(cuid_t cuid, const SocketHandle& socket)
+  : cuid_(cuid),
+    socket_(socket),
+    socketBuffer_(socket)
 {}
 
 HttpConnection::~HttpConnection() {}
@@ -95,11 +97,9 @@ std::string HttpConnection::eraseConfidentialInfo(const std::string& request)
 void HttpConnection::sendRequest(const SharedHandle<HttpRequest>& httpRequest)
 {
   std::string request = httpRequest->createRequest();
-  if(logger_->info()) {
-    logger_->info(MSG_SENDING_REQUEST,
+  A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
                   util::itos(cuid_).c_str(),
-                  eraseConfidentialInfo(request).c_str());
-  }
+                  eraseConfidentialInfo(request).c_str()));
   socketBuffer_.pushStr(request);
   socketBuffer_.send();
   SharedHandle<HttpRequestEntry> entry(new HttpRequestEntry(httpRequest));
@@ -110,11 +110,9 @@ void HttpConnection::sendProxyRequest
 (const SharedHandle<HttpRequest>& httpRequest)
 {
   std::string request = httpRequest->createProxyRequest();
-  if(logger_->info()) {
-    logger_->info(MSG_SENDING_REQUEST,
+  A2_LOG_INFO(fmt(MSG_SENDING_REQUEST,
                   util::itos(cuid_).c_str(),
-                  eraseConfidentialInfo(request).c_str());
-  }
+                  eraseConfidentialInfo(request).c_str()));
   socketBuffer_.pushStr(request);
   socketBuffer_.send();
   SharedHandle<HttpRequestEntry> entry(new HttpRequestEntry(httpRequest));
@@ -147,10 +145,9 @@ SharedHandle<HttpResponse> HttpConnection::receiveResponse()
   size_t putbackDataLength = proc->getPutBackDataLength();
   size -= putbackDataLength;
   socket_->readData(buf, size);
-  if(logger_->info()) {
-    logger_->info(MSG_RECEIVE_RESPONSE,
-                  util::itos(cuid_).c_str(), proc->getHeaderString().c_str());
-  }
+  A2_LOG_INFO(fmt(MSG_RECEIVE_RESPONSE,
+                  util::itos(cuid_).c_str(),
+                  proc->getHeaderString().c_str()));
   SharedHandle<HttpHeader> httpHeader = proc->getHttpResponseHeader();
   SharedHandle<HttpResponse> httpResponse(new HttpResponse());
   httpResponse->setCuid(cuid_);
diff --git a/src/HttpConnection.h b/src/HttpConnection.h
index 6d1c9524..9c7facea 100644
--- a/src/HttpConnection.h
+++ b/src/HttpConnection.h
@@ -50,7 +50,6 @@ class HttpRequest;
 class HttpResponse;
 class HttpHeaderProcessor;
 class Option;
-class Logger;
 class Segment;
 class SocketCore;
 
@@ -83,7 +82,6 @@ private:
   SharedHandle<SocketCore> socket_;
   SocketBuffer socketBuffer_;
   const Option* option_;
-  Logger* logger_;
 
   HttpRequestEntries outstandingHttpRequests_;
 
diff --git a/src/HttpInitiateConnectionCommand.cc b/src/HttpInitiateConnectionCommand.cc
index e625f470..0d9a11ab 100644
--- a/src/HttpInitiateConnectionCommand.cc
+++ b/src/HttpInitiateConnectionCommand.cc
@@ -43,11 +43,13 @@
 #include "DlAbortEx.h"
 #include "Option.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "Socket.h"
 #include "message.h"
 #include "prefs.h"
 #include "A2STR.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -56,8 +58,9 @@ HttpInitiateConnectionCommand::HttpInitiateConnectionCommand
  const SharedHandle<Request>& req,
  const SharedHandle<FileEntry>& fileEntry,
  RequestGroup* requestGroup,
- DownloadEngine* e):
-  InitiateConnectionCommand(cuid, req, fileEntry, requestGroup, e) {}
+ DownloadEngine* e)
+  : InitiateConnectionCommand(cuid, req, fileEntry, requestGroup, e)
+{}
 
 HttpInitiateConnectionCommand::~HttpInitiateConnectionCommand() {}
 
@@ -74,10 +77,8 @@ Command* HttpInitiateConnectionCommand::createNextCommand
        proxyRequest->getHost(), proxyRequest->getPort());
     std::string proxyMethod = resolveProxyMethod(getRequest()->getProtocol());
     if(!pooledSocket) {
-      if(getLogger()->info()) {
-        getLogger()->info(MSG_CONNECTING_TO_SERVER,
-                          util::itos(getCuid()).c_str(), addr.c_str(), port);
-      }
+      A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                      util::itos(getCuid()).c_str(), addr.c_str(), port));
       createSocket();
       getSocket()->establishConnection(addr, port);
 
@@ -129,10 +130,8 @@ Command* HttpInitiateConnectionCommand::createNextCommand
       getDownloadEngine()->popPooledSocket
       (resolvedAddresses, getRequest()->getPort());
     if(!pooledSocket) {
-      if(getLogger()->info()) {
-        getLogger()->info(MSG_CONNECTING_TO_SERVER,
-                          util::itos(getCuid()).c_str(), addr.c_str(), port);
-      }
+      A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                      util::itos(getCuid()).c_str(), addr.c_str(), port));
       createSocket();
       getSocket()->establishConnection(addr, port);
       getRequest()->setConnectedAddrInfo(hostname, addr, port);
diff --git a/src/HttpListenCommand.cc b/src/HttpListenCommand.cc
index 9a59a530..a0dd3c10 100644
--- a/src/HttpListenCommand.cc
+++ b/src/HttpListenCommand.cc
@@ -37,6 +37,7 @@
 #include "RecoverableException.h"
 #include "message.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "SocketCore.h"
 #include "HttpServerCommand.h"
 #include "CUIDCounter.h"
@@ -45,12 +46,15 @@
 #include "Option.h"
 #include "util.h"
 #include "A2STR.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-HttpListenCommand::HttpListenCommand
-(cuid_t cuid, DownloadEngine* e, int family):
-  Command(cuid), e_(e), family_(family) {}
+HttpListenCommand::HttpListenCommand(cuid_t cuid, DownloadEngine* e, int family)
+  : Command(cuid),
+    e_(e),
+    family_(family)
+{}
 
 HttpListenCommand::~HttpListenCommand()
 {
@@ -72,8 +76,8 @@ bool HttpListenCommand::execute()
       std::pair<std::string, uint16_t> peerInfo;
       socket->getPeerInfo(peerInfo);
 
-      getLogger()->info("XML-RPC: Accepted the connection from %s:%u.",
-                        peerInfo.first.c_str(), peerInfo.second);
+      A2_LOG_INFO(fmt("XML-RPC: Accepted the connection from %s:%u.",
+                      peerInfo.first.c_str(), peerInfo.second));
 
       HttpServerCommand* c =
         new HttpServerCommand(e_->newCUID(), e_, socket);
@@ -81,9 +85,7 @@ bool HttpListenCommand::execute()
       e_->addCommand(c);
     }
   } catch(RecoverableException& e) {
-    if(getLogger()->debug()) {
-      getLogger()->debug(MSG_ACCEPT_FAILURE, e, util::itos(getCuid()).c_str());
-    }
+    A2_LOG_DEBUG_EX(fmt(MSG_ACCEPT_FAILURE, util::itos(getCuid()).c_str()), e);
   }
   e_->addCommand(this);
   return false;
@@ -95,11 +97,9 @@ bool HttpListenCommand::bindPort(uint16_t port)
     e_->deleteSocketForReadCheck(serverSocket_, this);
   }
   serverSocket_.reset(new SocketCore());
-  if(getLogger()->info()) {
-    getLogger()->info("CUID#%s - Setting up HttpListenCommand for IPv%d",
-                      util::itos(getCuid()).c_str(),
-                      family_ == AF_INET?4:6);
-  }
+  A2_LOG_INFO(fmt("CUID#%s - Setting up HttpListenCommand for IPv%d",
+                  util::itos(getCuid()).c_str(),
+                  family_ == AF_INET?4:6));
   try {
     int flags = 0;
     if(e_->getOption()->getAsBool(PREF_XML_RPC_LISTEN_ALL)) {
@@ -108,17 +108,16 @@ bool HttpListenCommand::bindPort(uint16_t port)
     serverSocket_->bind(A2STR::NIL, port, family_, flags);
     serverSocket_->beginListen();
     serverSocket_->setNonBlockingMode();
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_LISTENING_PORT,
-                        util::itos(getCuid()).c_str(), port);
-    }
+    A2_LOG_INFO(fmt(MSG_LISTENING_PORT,
+                    util::itos(getCuid()).c_str(), port));
     e_->addSocketForReadCheck(serverSocket_, this);
     return true;
   } catch(RecoverableException& e) {
-    getLogger()->error("Failed to setup XML-RPC server for IPv%d",
-                       family_ == AF_INET?4:6);
-    getLogger()->error(MSG_BIND_FAILURE, e,
-                       util::itos(getCuid()).c_str(), port);
+    A2_LOG_ERROR(fmt("Failed to setup XML-RPC server for IPv%d",
+                     family_ == AF_INET?4:6));
+    A2_LOG_ERROR_EX(fmt(MSG_BIND_FAILURE,
+                        util::itos(getCuid()).c_str(), port),
+                    e);
     if(serverSocket_) {
       e_->deleteSocketForReadCheck(serverSocket_, this);
     }
diff --git a/src/HttpRequestCommand.cc b/src/HttpRequestCommand.cc
index 54bfb91c..8d9919dd 100644
--- a/src/HttpRequestCommand.cc
+++ b/src/HttpRequestCommand.cc
@@ -56,6 +56,8 @@
 #include "PieceStorage.h"
 #include "DefaultBtProgressInfoFile.h"
 #include "Logger.h"
+#include "LogFactory.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -67,8 +69,8 @@ HttpRequestCommand::HttpRequestCommand
  const HttpConnectionHandle& httpConnection,
  DownloadEngine* e,
  const SocketHandle& s)
-  :AbstractCommand(cuid, req, fileEntry, requestGroup, e, s),
-   httpConnection_(httpConnection)
+  : AbstractCommand(cuid, req, fileEntry, requestGroup, e, s),
+    httpConnection_(httpConnection)
 {
   setTimeout(getOption()->getAsInt(PREF_CONNECT_TIMEOUT));
   disableReadCheckSocket();
@@ -150,10 +152,8 @@ bool HttpRequestCommand::executeInternal() {
           getRequest()->getProtocol() == Request::PROTO_HTTPS)) {
         if(getFileEntry()->getPath().empty() &&
            getRequest()->getFile().empty()) {
-          if(getLogger()->debug()) {
-            getLogger()->debug("conditional-get is disabled because file name"
-                               "is not available.");
-          }
+          A2_LOG_DEBUG("Conditional-Get is disabled because file name"
+                       " is not available.");
         } else {
           if(getFileEntry()->getPath().empty()) {
             getFileEntry()->setPath
diff --git a/src/HttpResponse.cc b/src/HttpResponse.cc
index 1abe0148..963b84bd 100644
--- a/src/HttpResponse.cc
+++ b/src/HttpResponse.cc
@@ -45,6 +45,7 @@
 #include "DlAbortEx.h"
 #include "DlRetryEx.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "A2STR.h"
 #include "CookieStorage.h"
 #include "AuthConfigFactory.h"
@@ -56,8 +57,8 @@
 
 namespace aria2 {
 
-HttpResponse::HttpResponse():cuid_(0),
-                             logger_(LogFactory::getInstance())
+HttpResponse::HttpResponse()
+  : cuid_(0)
 {}
 
 HttpResponse::~HttpResponse() {}
@@ -117,10 +118,9 @@ std::string HttpResponse::determinFilename() const
       return file;
     }
   } else {
-    if(logger_->info()) {
-      logger_->info(MSG_CONTENT_DISPOSITION_DETECTED,
-                    util::itos(cuid_).c_str(), contentDisposition.c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_CONTENT_DISPOSITION_DETECTED,
+                    util::itos(cuid_).c_str(),
+                    contentDisposition.c_str()));
     return contentDisposition;
   }
 }
@@ -150,10 +150,9 @@ void HttpResponse::processRedirect()
 {
   
   if(httpRequest_->getRequest()->redirectUri(getRedirectURI())) {
-    if(logger_->info()) {
-      logger_->info(MSG_REDIRECT, util::itos(cuid_).c_str(),
-                    httpRequest_->getRequest()->getCurrentUri().c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_REDIRECT,
+                    util::itos(cuid_).c_str(),
+                    httpRequest_->getRequest()->getCurrentUri().c_str()));
   } else {
     throw DL_RETRY_EX
       (StringFormat("CUID#%s - Redirect to %s failed. It may not be a valid"
diff --git a/src/HttpResponse.h b/src/HttpResponse.h
index 807b6083..f818e7cc 100644
--- a/src/HttpResponse.h
+++ b/src/HttpResponse.h
@@ -47,7 +47,6 @@ namespace aria2 {
 
 class HttpRequest;
 class HttpHeader;
-class Logger;
 class StreamFilter;
 
 class HttpResponse {
@@ -55,7 +54,6 @@ private:
   cuid_t cuid_;
   SharedHandle<HttpRequest> httpRequest_;
   SharedHandle<HttpHeader> httpHeader_;
-  Logger* logger_;
 public:
   HttpResponse();
   
diff --git a/src/HttpResponseCommand.cc b/src/HttpResponseCommand.cc
index 01628a3f..82ac7333 100644
--- a/src/HttpResponseCommand.cc
+++ b/src/HttpResponseCommand.cc
@@ -58,6 +58,7 @@
 #include "message.h"
 #include "prefs.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "HttpSkipResponseCommand.h"
 #include "HttpHeader.h"
 #include "LogFactory.h"
@@ -109,11 +110,11 @@ SharedHandle<StreamFilter> getContentEncodingStreamFilter
   if(httpResponse->isContentEncodingSpecified()) {
     filter = httpResponse->getContentEncodingStreamFilter();
     if(!filter) {
-      LogFactory::getInstance()->info
-        ("Content-Encoding %s is specified, but the current implementation"
-         "doesn't support it. The decoding process is skipped and the"
-         "downloaded content will be still encoded.",
-         httpResponse->getContentEncoding().c_str());
+      A2_LOG_INFO
+        (fmt("Content-Encoding %s is specified, but the current implementation"
+             "doesn't support it. The decoding process is skipped and the"
+             "downloaded content will be still encoded.",
+             httpResponse->getContentEncoding().c_str()));
     } else {
       filter->init();
       filter->installDelegate(delegate);
@@ -134,8 +135,8 @@ HttpResponseCommand::HttpResponseCommand
  const HttpConnectionHandle& httpConnection,
  DownloadEngine* e,
  const SocketHandle& s)
-  :AbstractCommand(cuid, req, fileEntry, requestGroup, e, s),
-   httpConnection_(httpConnection)
+  : AbstractCommand(cuid, req, fileEntry, requestGroup, e, s),
+    httpConnection_(httpConnection)
 {}
 
 HttpResponseCommand::~HttpResponseCommand() {}
@@ -176,9 +177,9 @@ bool HttpResponseCommand::executeInternal()
       getPieceStorage()->markAllPiecesDone();
       // Just set checksum verification done.
       getDownloadContext()->setChecksumVerified(true);
-      getLogger()->notice(MSG_DOWNLOAD_ALREADY_COMPLETED,
-                          util::itos(getRequestGroup()->getGID()).c_str(),
-                          getRequestGroup()->getFirstFilePath().c_str());
+      A2_LOG_NOTICE(fmt(MSG_DOWNLOAD_ALREADY_COMPLETED,
+                        util::itos(getRequestGroup()->getGID()).c_str(),
+                        getRequestGroup()->getFirstFilePath().c_str()));
       poolConnection();
       getFileEntry()->poolRequest(getRequest());
       return true;
@@ -382,9 +383,9 @@ bool HttpResponseCommand::handleOtherEncoding
     getRequestGroup()->initPieceStorage();
     getPieceStorage()->markAllPiecesDone();
     getDownloadContext()->setChecksumVerified(true);
-    getLogger()->notice(MSG_DOWNLOAD_ALREADY_COMPLETED,
-                        util::itos(getRequestGroup()->getGID()).c_str(),
-                        getRequestGroup()->getFirstFilePath().c_str());
+    A2_LOG_NOTICE(fmt(MSG_DOWNLOAD_ALREADY_COMPLETED,
+                      util::itos(getRequestGroup()->getGID()).c_str(),
+                      getRequestGroup()->getFirstFilePath().c_str()));
     poolConnection();
     return true;
   }
diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 4f1e5e92..fd8f9b6b 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -46,20 +46,21 @@
 #include "Logger.h"
 #include "Base64.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-HttpServer::HttpServer(const SharedHandle<SocketCore>& socket,
-                       DownloadEngine* e):
-  socket_(socket),
-  socketBuffer_(socket),
-  e_(e),
-  headerProcessor_(new HttpHeaderProcessor()),
-  logger_(LogFactory::getInstance()),
-  keepAlive_(true),
-  gzip_(false),
-  acceptsPersistentConnection_(true),
-  acceptsGZip_(false)
+HttpServer::HttpServer
+(const SharedHandle<SocketCore>& socket,
+ DownloadEngine* e)
+ : socket_(socket),
+   socketBuffer_(socket),
+   e_(e),
+   headerProcessor_(new HttpHeaderProcessor()),
+   keepAlive_(true),
+   gzip_(false),
+   acceptsPersistentConnection_(true),
+   acceptsGZip_(false)
 {}
 
 HttpServer::~HttpServer() {}
@@ -83,8 +84,8 @@ SharedHandle<HttpHeader> HttpServer::receiveRequest()
 
   SharedHandle<HttpHeader> header = headerProcessor_->getHttpRequestHeader();
   if(header) {
-    logger_->info("HTTP Server received request\n%s",
-                  headerProcessor_->getHeaderString().c_str());
+    A2_LOG_INFO(fmt("HTTP Server received request\n%s",
+                    headerProcessor_->getHeaderString().c_str()));
     lastRequestHeader_ = header;
     lastBody_.clear();
     lastBody_.str("");
@@ -165,9 +166,7 @@ void HttpServer::feedResponse(const std::string& status,
   }
 
   header += "\r\n";
-  if(logger_->debug()) {
-    logger_->debug("HTTP Server sends response:\n%s", header.c_str());
-  }
+  A2_LOG_DEBUG(fmt("HTTP Server sends response:\n%s", header.c_str()));
   socketBuffer_.pushStr(header);
   socketBuffer_.pushStr(text);
 }
diff --git a/src/HttpServer.h b/src/HttpServer.h
index 19f5358f..56b982f3 100644
--- a/src/HttpServer.h
+++ b/src/HttpServer.h
@@ -50,7 +50,6 @@ class SocketCore;
 class HttpHeader;
 class HttpHeaderProcessor;
 class DownloadEngine;
-class Logger;
 
 class HttpServer {
 private:
@@ -58,7 +57,6 @@ private:
   SocketBuffer socketBuffer_;
   DownloadEngine* e_;
   SharedHandle<HttpHeaderProcessor> headerProcessor_;
-  Logger* logger_;
   SharedHandle<HttpHeader> lastRequestHeader_;
   uint64_t lastContentLength_;
   std::stringstream lastBody_;
diff --git a/src/HttpServerBodyCommand.cc b/src/HttpServerBodyCommand.cc
index 7246ef16..441ed40b 100644
--- a/src/HttpServerBodyCommand.cc
+++ b/src/HttpServerBodyCommand.cc
@@ -38,6 +38,7 @@
 #include "HttpServer.h"
 #include "HttpHeader.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "RequestGroup.h"
 #include "RequestGroupMan.h"
 #include "RecoverableException.h"
@@ -51,6 +52,7 @@
 #include "XmlRpcResponse.h"
 #include "wallclock.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -58,11 +60,11 @@ HttpServerBodyCommand::HttpServerBodyCommand
 (cuid_t cuid,
  const SharedHandle<HttpServer>& httpServer,
  DownloadEngine* e,
- const SharedHandle<SocketCore>& socket):
-  Command(cuid),
-  e_(e),
-  socket_(socket),
-  httpServer_(httpServer)
+ const SharedHandle<SocketCore>& socket)
+  : Command(cuid),
+    e_(e),
+    socket_(socket),
+    httpServer_(httpServer)
 {
   setStatus(Command::STATUS_ONESHOT_REALTIME);
   e_->addSocketForReadCheck(socket_, this);
@@ -108,7 +110,7 @@ bool HttpServerBodyCommand::execute()
       } 
     } else {
       if(timeoutTimer_.difference(global::wallclock) >= 30) {
-        getLogger()->info("HTTP request body timeout.");
+        A2_LOG_INFO("HTTP request body timeout.");
         return true;
       } else {
         e_->addCommand(this);
@@ -116,11 +118,10 @@ bool HttpServerBodyCommand::execute()
       }
     }
   } catch(RecoverableException& e) {
-    if(getLogger()->info()) {
-      getLogger()->info
-        ("CUID#%s - Error occurred while reading HTTP request body",
-         e, util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO_EX
+      (fmt("CUID#%s - Error occurred while reading HTTP request body",
+           util::itos(getCuid()).c_str()),
+       e);
     return true;
   }
 
diff --git a/src/HttpServerCommand.cc b/src/HttpServerCommand.cc
index 0a76d011..4e7d42d0 100644
--- a/src/HttpServerCommand.cc
+++ b/src/HttpServerCommand.cc
@@ -38,6 +38,7 @@
 #include "HttpServer.h"
 #include "HttpHeader.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "RequestGroup.h"
 #include "RequestGroupMan.h"
 #include "HttpServerBodyCommand.h"
@@ -47,15 +48,18 @@
 #include "Option.h"
 #include "util.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-HttpServerCommand::HttpServerCommand(cuid_t cuid, DownloadEngine* e,
-                                     const SharedHandle<SocketCore>& socket):
-  Command(cuid),
-  e_(e),
-  socket_(socket),
-  httpServer_(new HttpServer(socket, e))
+HttpServerCommand::HttpServerCommand
+(cuid_t cuid,
+ DownloadEngine* e,
+ const SharedHandle<SocketCore>& socket)
+  : Command(cuid),
+    e_(e),
+    socket_(socket),
+    httpServer_(new HttpServer(socket, e))
 {
   setStatus(Command::STATUS_ONESHOT_REALTIME);
   e_->addSocketForReadCheck(socket_, this);
@@ -68,14 +72,15 @@ HttpServerCommand::HttpServerCommand(cuid_t cuid, DownloadEngine* e,
 #endif // !HAVE_LIBZ
 }
 
-HttpServerCommand::HttpServerCommand(cuid_t cuid,
-                                     const SharedHandle<HttpServer>& httpServer,
-                                     DownloadEngine* e,
-                                     const SharedHandle<SocketCore>& socket):
-  Command(cuid),
-  e_(e),
-  socket_(socket),
-  httpServer_(httpServer)
+HttpServerCommand::HttpServerCommand
+(cuid_t cuid,
+ const SharedHandle<HttpServer>& httpServer,
+ DownloadEngine* e,
+ const SharedHandle<SocketCore>& socket)
+  : Command(cuid),
+    e_(e),
+    socket_(socket),
+    httpServer_(httpServer)
 {
   e_->addSocketForReadCheck(socket_, this);
 }
@@ -115,10 +120,10 @@ bool HttpServerCommand::execute()
       if(static_cast<uint64_t>
          (e_->getOption()->getAsInt(PREF_XML_RPC_MAX_REQUEST_SIZE)) <
          httpServer_->getContentLength()) {
-        getLogger()->info("Request too long. ContentLength=%s."
-                          " See --xml-rpc-max-request-size option to loose"
-                          " this limitation.",
-                          util::uitos(httpServer_->getContentLength()).c_str());
+        A2_LOG_INFO(fmt("Request too long. ContentLength=%s."
+                        " See --xml-rpc-max-request-size option to loose"
+                        " this limitation.",
+                        util::uitos(httpServer_->getContentLength()).c_str()));
         return true;
       }
       Command* command = new HttpServerBodyCommand(getCuid(), httpServer_, e_,
@@ -128,7 +133,7 @@ bool HttpServerCommand::execute()
       return true;
     } else {
       if(timeoutTimer_.difference(global::wallclock) >= 30) {
-        getLogger()->info("HTTP request timeout.");
+        A2_LOG_INFO("HTTP request timeout.");
         return true;
       } else {
         e_->addCommand(this);
@@ -136,10 +141,9 @@ bool HttpServerCommand::execute()
       }
     }
   } catch(RecoverableException& e) {
-    if(getLogger()->info()) {
-      getLogger()->info("CUID#%s - Error occurred while reading HTTP request",
-                        e, util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO_EX(fmt("CUID#%s - Error occurred while reading HTTP request",
+                       util::itos(getCuid()).c_str()),
+                   e);
     return true;
   }
 
diff --git a/src/HttpServerResponseCommand.cc b/src/HttpServerResponseCommand.cc
index c234c76a..f282cf45 100644
--- a/src/HttpServerResponseCommand.cc
+++ b/src/HttpServerResponseCommand.cc
@@ -37,11 +37,13 @@
 #include "DownloadEngine.h"
 #include "HttpServer.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "HttpServerCommand.h"
 #include "RequestGroupMan.h"
 #include "RecoverableException.h"
 #include "wallclock.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -49,11 +51,11 @@ HttpServerResponseCommand::HttpServerResponseCommand
 (cuid_t cuid,
  const SharedHandle<HttpServer>& httpServer,
  DownloadEngine* e,
- const SharedHandle<SocketCore>& socket):
-  Command(cuid),
-  e_(e),
-  socket_(socket),
-  httpServer_(httpServer)
+ const SharedHandle<SocketCore>& socket)
+ : Command(cuid),
+   e_(e),
+   socket_(socket),
+   httpServer_(httpServer)
 {
   setStatus(Command::STATUS_ONESHOT_REALTIME); 
   e_->addSocketForWriteCheck(socket_, this);
@@ -72,33 +74,27 @@ bool HttpServerResponseCommand::execute()
   try {
     httpServer_->sendResponse();
   } catch(RecoverableException& e) {
-    if(getLogger()->info()) {
-      getLogger()->info
-        ("CUID#%s - Error occurred while transmitting response body.",
-         e, util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO_EX
+      (fmt("CUID#%s - Error occurred while transmitting response body.",
+           util::itos(getCuid()).c_str()),
+       e);
     return true;
   }
   if(httpServer_->sendBufferIsEmpty()) {
-    if(getLogger()->info()) {
-      getLogger()->info("CUID#%s - HttpServer: all response transmitted.",
-                        util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO(fmt("CUID#%s - HttpServer: all response transmitted.",
+                    util::itos(getCuid()).c_str()));
     if(httpServer_->supportsPersistentConnection()) {
-      if(getLogger()->info()) {
-        getLogger()->info("CUID#%s - Persist connection.",
-                          util::itos(getCuid()).c_str());
-      }
+      A2_LOG_INFO(fmt("CUID#%s - Persist connection.",
+                      util::itos(getCuid()).c_str()));
       e_->addCommand
         (new HttpServerCommand(getCuid(), httpServer_, e_, socket_));
     }
     return true;
   } else {
     if(timeoutTimer_.difference(global::wallclock) >= 10) {
-      if(getLogger()->info()) {
-        getLogger()->info("CUID#%s - HttpServer: Timeout while trasmitting"
-                          " response.", util::itos(getCuid()).c_str());
-      }
+      A2_LOG_INFO(fmt("CUID#%s - HttpServer: Timeout while trasmitting"
+                      " response.",
+                      util::itos(getCuid()).c_str()));
       return true;
     } else {
       e_->addCommand(this);
diff --git a/src/HttpSkipResponseCommand.cc b/src/HttpSkipResponseCommand.cc
index b38ea7d0..96ca1bbe 100644
--- a/src/HttpSkipResponseCommand.cc
+++ b/src/HttpSkipResponseCommand.cc
@@ -41,10 +41,12 @@
 #include "Request.h"
 #include "DownloadEngine.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "HttpRequest.h"
 #include "Segment.h"
 #include "util.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "DlAbortEx.h"
 #include "HttpHeader.h"
 #include "prefs.h"
@@ -68,14 +70,14 @@ HttpSkipResponseCommand::HttpSkipResponseCommand
  const SharedHandle<HttpConnection>& httpConnection,
  const SharedHandle<HttpResponse>& httpResponse,
  DownloadEngine* e,
- const SharedHandle<SocketCore>& s):
-  AbstractCommand(cuid, req, fileEntry, requestGroup, e, s),
-  httpConnection_(httpConnection),
-  httpResponse_(httpResponse),
-  streamFilter_(new NullSinkStreamFilter()),
-  sinkFilterOnly_(true),
-  totalLength_(httpResponse_->getEntityLength()),
-  receivedBytes_(0)
+ const SharedHandle<SocketCore>& s)
+  : AbstractCommand(cuid, req, fileEntry, requestGroup, e, s),
+    httpConnection_(httpConnection),
+    httpResponse_(httpResponse),
+    streamFilter_(new NullSinkStreamFilter()),
+    sinkFilterOnly_(true),
+    totalLength_(httpResponse_->getEntityLength()),
+    receivedBytes_(0)
 {}
 
 HttpSkipResponseCommand::~HttpSkipResponseCommand() {}
@@ -133,9 +135,7 @@ bool HttpSkipResponseCommand::executeInternal()
       throw DL_RETRY_EX(EX_GOT_EOF);
     }
   } catch(RecoverableException& e) {
-    if(getLogger()->debug()) {
-      getLogger()->debug(EX_EXCEPTION_CAUGHT, e);
-    }
+    A2_LOG_DEBUG_EX(EX_EXCEPTION_CAUGHT, e)
     return processResponse();
   }
 
diff --git a/src/InitiateConnectionCommand.cc b/src/InitiateConnectionCommand.cc
index e58da6c7..ca96d12a 100644
--- a/src/InitiateConnectionCommand.cc
+++ b/src/InitiateConnectionCommand.cc
@@ -37,6 +37,7 @@
 #include "DownloadEngine.h"
 #include "Option.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "message.h"
 #include "prefs.h"
 #include "NameResolver.h"
@@ -48,6 +49,7 @@
 #include "InitiateConnectionCommandFactory.h"
 #include "util.h"
 #include "RecoverableException.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -56,8 +58,8 @@ InitiateConnectionCommand::InitiateConnectionCommand
  const SharedHandle<Request>& req,
  const SharedHandle<FileEntry>& fileEntry,
  RequestGroup* requestGroup,
- DownloadEngine* e):
-  AbstractCommand(cuid, req, fileEntry, requestGroup, e)
+ DownloadEngine* e)
+  : AbstractCommand(cuid, req, fileEntry, requestGroup, e)
 {
   setTimeout(getOption()->getAsInt(PREF_DNS_TIMEOUT));
   // give a chance to be executed in the next loop in DownloadEngine
@@ -97,11 +99,10 @@ bool InitiateConnectionCommand::executeInternal() {
     // TODO ipaddr might not be used if pooled sockt was found.
     getDownloadEngine()->markBadIPAddress(hostname, ipaddr, port);
     if(!getDownloadEngine()->findCachedIPAddress(hostname, port).empty()) {
-      if(getLogger()->info()) {
-        getLogger()->info(EX_EXCEPTION_CAUGHT, ex);
-        getLogger()->info(MSG_CONNECT_FAILED_AND_RETRY,
-                          util::itos(getCuid()).c_str(), ipaddr.c_str(), port);
-      }
+      A2_LOG_INFO_EX(EX_EXCEPTION_CAUGHT, ex);
+      A2_LOG_INFO(fmt(MSG_CONNECT_FAILED_AND_RETRY,
+                      util::itos(getCuid()).c_str(),
+                      ipaddr.c_str(), port));
       Command* command =
         InitiateConnectionCommandFactory::createInitiateConnectionCommand
         (getCuid(), getRequest(), getFileEntry(), getRequestGroup(),
diff --git a/src/InitiatorMSEHandshakeCommand.cc b/src/InitiatorMSEHandshakeCommand.cc
index d9bf4289..c59d95c5 100644
--- a/src/InitiatorMSEHandshakeCommand.cc
+++ b/src/InitiatorMSEHandshakeCommand.cc
@@ -41,6 +41,7 @@
 #include "prefs.h"
 #include "Socket.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "Peer.h"
 #include "PeerConnection.h"
 #include "BtRuntime.h"
@@ -54,6 +55,7 @@
 #include "DownloadContext.h"
 #include "bittorrent_helper.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -63,13 +65,12 @@ InitiatorMSEHandshakeCommand::InitiatorMSEHandshakeCommand
  const SharedHandle<Peer>& p,
  DownloadEngine* e,
  const SharedHandle<BtRuntime>& btRuntime,
- const SharedHandle<SocketCore>& s):
-
-  PeerAbstractCommand(cuid, p, e, s),
-  requestGroup_(requestGroup),
-  btRuntime_(btRuntime),
-  sequence_(INITIATOR_SEND_KEY),
-  mseHandshake_(new MSEHandshake(cuid, s, getOption().get()))
+ const SharedHandle<SocketCore>& s)
+  : PeerAbstractCommand(cuid, p, e, s),
+    requestGroup_(requestGroup),
+    btRuntime_(btRuntime),
+    sequence_(INITIATOR_SEND_KEY),
+    mseHandshake_(new MSEHandshake(cuid, s, getOption().get()))
 {
   disableReadCheckSocket();
   setWriteCheckSocket(getSocket());
@@ -172,12 +173,9 @@ bool InitiatorMSEHandshakeCommand::executeInternal() {
 bool InitiatorMSEHandshakeCommand::prepareForNextPeer(time_t wait)
 {
   if(getOption()->getAsBool(PREF_BT_REQUIRE_CRYPTO)) {
-    if(getLogger()->info()) {
-      getLogger()->info
-        ("CUID#%s - Establishing connection using legacy BitTorrent"
-         " handshake is disabled by preference.",
-         util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO(fmt("CUID#%s - Establishing connection using legacy BitTorrent"
+                    " handshake is disabled by preference.",
+                    util::itos(getCuid()).c_str()));
     if(peerStorage_->isPeerAvailable() && btRuntime_->lessThanEqMinPeers()) {
       SharedHandle<Peer> peer = peerStorage_->getUnusedPeer();
       peer->usedBy(getDownloadEngine()->newCUID());
@@ -191,10 +189,8 @@ bool InitiatorMSEHandshakeCommand::prepareForNextPeer(time_t wait)
     return true;
   } else {
     // try legacy BitTorrent handshake
-    if(getLogger()->info()) {
-      getLogger()->info("CUID#%s - Retry using legacy BitTorrent handshake.",
-                        util::itos(getCuid()).c_str());
-    }
+    A2_LOG_INFO(fmt("CUID#%s - Retry using legacy BitTorrent handshake.",
+                    util::itos(getCuid()).c_str()));
     PeerInitiateConnectionCommand* command =
       new PeerInitiateConnectionCommand(getCuid(), requestGroup_, getPeer(),
                                         getDownloadEngine(), btRuntime_, false);
diff --git a/src/IteratableChecksumValidator.cc b/src/IteratableChecksumValidator.cc
index 02f41869..26f75db7 100644
--- a/src/IteratableChecksumValidator.cc
+++ b/src/IteratableChecksumValidator.cc
@@ -40,8 +40,6 @@
 #include "message.h"
 #include "PieceStorage.h"
 #include "MessageDigest.h"
-#include "LogFactory.h"
-#include "Logger.h"
 #include "DiskAdaptor.h"
 #include "FileEntry.h"
 #include "BitfieldMan.h"
@@ -54,12 +52,12 @@ namespace aria2 {
 
 IteratableChecksumValidator::IteratableChecksumValidator
 (const SharedHandle<DownloadContext>& dctx,
- const PieceStorageHandle& pieceStorage):
-  dctx_(dctx),
-  pieceStorage_(pieceStorage),
-  currentOffset_(0),
-  logger_(LogFactory::getInstance()),
-  buffer_(0) {}
+ const PieceStorageHandle& pieceStorage)
+  : dctx_(dctx),
+    pieceStorage_(pieceStorage),
+    currentOffset_(0),
+    buffer_(0)
+{}
 
 IteratableChecksumValidator::~IteratableChecksumValidator()
 {
diff --git a/src/IteratableChecksumValidator.h b/src/IteratableChecksumValidator.h
index 6f788c62..bdc20f82 100644
--- a/src/IteratableChecksumValidator.h
+++ b/src/IteratableChecksumValidator.h
@@ -41,7 +41,6 @@ namespace aria2 {
 
 class DownloadContext;
 class PieceStorage;
-class Logger;
 class MessageDigest;
 
 class IteratableChecksumValidator:public IteratableValidator
@@ -55,10 +54,7 @@ private:
 
   SharedHandle<MessageDigest> ctx_;
 
-  Logger* logger_;
-
   unsigned char* buffer_;
-
 public:
   IteratableChecksumValidator(const SharedHandle<DownloadContext>& dctx,
                               const SharedHandle<PieceStorage>& pieceStorage);
diff --git a/src/IteratableChunkChecksumValidator.cc b/src/IteratableChunkChecksumValidator.cc
index 7b251b56..c234cbf6 100644
--- a/src/IteratableChunkChecksumValidator.cc
+++ b/src/IteratableChunkChecksumValidator.cc
@@ -50,6 +50,7 @@
 #include "Logger.h"
 #include "MessageDigest.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "DlAbortEx.h"
 
 namespace aria2 {
@@ -57,15 +58,16 @@ namespace aria2 {
 #define BUFSIZE (256*1024)
 #define ALIGNMENT 512
 
-IteratableChunkChecksumValidator::
-IteratableChunkChecksumValidator(const SharedHandle<DownloadContext>& dctx,
-                                 const PieceStorageHandle& pieceStorage):
-  dctx_(dctx),
-  pieceStorage_(pieceStorage),
-  bitfield_(new BitfieldMan(dctx_->getPieceLength(), dctx_->getTotalLength())),
-  currentIndex_(0),
-  logger_(LogFactory::getInstance()),
-  buffer_(0) {}
+IteratableChunkChecksumValidator::IteratableChunkChecksumValidator
+(const SharedHandle<DownloadContext>& dctx,
+ const PieceStorageHandle& pieceStorage)
+  : dctx_(dctx),
+    pieceStorage_(pieceStorage),
+    bitfield_(new BitfieldMan(dctx_->getPieceLength(),
+                              dctx_->getTotalLength())),
+    currentIndex_(0),
+    buffer_(0)
+{}
 
 IteratableChunkChecksumValidator::~IteratableChunkChecksumValidator()
 {
@@ -86,21 +88,19 @@ void IteratableChunkChecksumValidator::validateChunk()
       if(actualChecksum == dctx_->getPieceHashes()[currentIndex_]) {
         bitfield_->setBit(currentIndex_);
       } else {
-        if(logger_->info()) {
-          logger_->info(EX_INVALID_CHUNK_CHECKSUM,
+        A2_LOG_INFO(fmt(EX_INVALID_CHUNK_CHECKSUM,
                         static_cast<unsigned long>(currentIndex_),
                         util::itos(getCurrentOffset(), true).c_str(),
                         dctx_->getPieceHashes()[currentIndex_].c_str(),
-                        actualChecksum.c_str());
-        }
+                        actualChecksum.c_str()));
         bitfield_->unsetBit(currentIndex_);
       }
     } catch(RecoverableException& ex) {
-      if(logger_->debug()) {
-        logger_->debug("Caught exception while validating piece index=%lu."
-                       " Some part of file may be missing. Continue operation.",
-                       ex, static_cast<unsigned long>(currentIndex_));
-      }
+      A2_LOG_DEBUG_EX(fmt("Caught exception while validating piece index=%lu."
+                          " Some part of file may be missing."
+                          " Continue operation.",
+                          static_cast<unsigned long>(currentIndex_)),
+                      ex);
       bitfield_->unsetBit(currentIndex_);
     }
 
diff --git a/src/IteratableChunkChecksumValidator.h b/src/IteratableChunkChecksumValidator.h
index ff011ff2..46f41b5c 100644
--- a/src/IteratableChunkChecksumValidator.h
+++ b/src/IteratableChunkChecksumValidator.h
@@ -42,7 +42,6 @@ namespace aria2 {
 class DownloadContext;
 class PieceStorage;
 class BitfieldMan;
-class Logger;
 class MessageDigest;
 
 class IteratableChunkChecksumValidator:public IteratableValidator
@@ -52,7 +51,6 @@ private:
   SharedHandle<PieceStorage> pieceStorage_;
   SharedHandle<BitfieldMan> bitfield_;
   size_t currentIndex_;
-  Logger* logger_;
   SharedHandle<MessageDigest> ctx_;
   unsigned char* buffer_;
 
diff --git a/src/KqueueEventPoll.cc b/src/KqueueEventPoll.cc
index dfa500b4..8e30440d 100644
--- a/src/KqueueEventPoll.cc
+++ b/src/KqueueEventPoll.cc
@@ -43,6 +43,7 @@
 #include "LogFactory.h"
 #include "Logger.h"
 #include "util.h"
+#include "fmt.h"
 
 #ifdef KEVENT_UDATA_INTPTR_T
 # define PTR_TO_UDATA(X) (reinterpret_cast<intptr_t>(X))
@@ -52,8 +53,9 @@
 
 namespace aria2 {
 
-KqueueEventPoll::KSocketEntry::KSocketEntry(sock_t s):
-  SocketEntry<KCommandEvent, KADNSEvent>(s) {}
+KqueueEventPoll::KSocketEntry::KSocketEntry(sock_t s)
+  : SocketEntry<KCommandEvent, KADNSEvent>(s)
+{}
 
 int accumulateEvent(int events, const KqueueEventPoll::KEvent& event)
 {
@@ -85,10 +87,9 @@ size_t KqueueEventPoll::KSocketEntry::getEvents
   return 2;
 }
 
-KqueueEventPoll::KqueueEventPoll():
-  kqEventsSize_(KQUEUE_EVENTS_MAX),
-  kqEvents_(new struct kevent[kqEventsSize_]),
-  logger_(LogFactory::getInstance())
+KqueueEventPoll::KqueueEventPoll()
+  : kqEventsSize_(KQUEUE_EVENTS_MAX),
+    kqEvents_(new struct kevent[kqEventsSize_])
 {
   kqfd_ = kqueue();
 }
@@ -100,9 +101,10 @@ KqueueEventPoll::~KqueueEventPoll()
     while((r = close(kqfd_)) == -1 && errno == EINTR);
     int errNum = errno;
     if(r == -1) {
-      logger_->error("Error occurred while closing kqueue file descriptor"
-                     " %d: %s",
-                     kqfd_, util::safeStrerror(errNum).c_str());
+      A2_LOG_ERROR(fmt("Error occurred while closing kqueue file descriptor"
+                       " %d: %s",
+                       kqfd_,
+                       util::safeStrerror(errNum).c_str()));
     }
   }
   delete [] kqEvents_;
@@ -192,10 +194,9 @@ bool KqueueEventPoll::addEvents
   r = kevent(kqfd_, changelist, n, changelist, 0, &zeroTimeout);
   int errNum = errno;
   if(r == -1) {
-    if(logger_->debug()) {
-      logger_->debug("Failed to add socket event %d:%s",
-                     socket, util::safeStrerror(errNum).c_str());
-    }
+    A2_LOG_DEBUG(fmt("Failed to add socket event %d:%s",
+                     socket,
+                     util::safeStrerror(errNum).c_str()));
     return false;
   } else {
     return true;
@@ -236,18 +237,14 @@ bool KqueueEventPoll::deleteEvents(sock_t socket,
       socketEntries_.erase(i);
     }
     if(r == -1) {
-      if(logger_->debug()) {
-        logger_->debug("Failed to delete socket event:%s",
-                       util::safeStrerror(errNum).c_str());
-      }
+      A2_LOG_DEBUG(fmt("Failed to delete socket event:%s",
+                       util::safeStrerror(errNum).c_str()));
       return false;
     } else {
       return true;
     }
   } else {
-    if(logger_->debug()) {
-      logger_->debug("Socket %d is not found in SocketEntries.", socket);
-    }
+    A2_LOG_DEBUG(fmt("Socket %d is not found in SocketEntries.", socket));
     return false;
   }
 }
diff --git a/src/KqueueEventPoll.h b/src/KqueueEventPoll.h
index cb9deeaf..37523efa 100644
--- a/src/KqueueEventPoll.h
+++ b/src/KqueueEventPoll.h
@@ -50,8 +50,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class KqueueEventPoll : public EventPoll {
 private:
   class KSocketEntry;
@@ -89,8 +87,6 @@ private:
 
   static const size_t KQUEUE_EVENTS_MAX = 1024;
 
-  Logger* logger_;
-
   bool addEvents(sock_t socket, const KEvent& event);
 
   bool deleteEvents(sock_t socket, const KEvent& event);
diff --git a/src/LibgnutlsTLSContext.cc b/src/LibgnutlsTLSContext.cc
index f4ca2baf..6bd9e4ae 100644
--- a/src/LibgnutlsTLSContext.cc
+++ b/src/LibgnutlsTLSContext.cc
@@ -41,13 +41,14 @@
 #include "LogFactory.h"
 #include "Logger.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "message.h"
 
 namespace aria2 {
 
-TLSContext::TLSContext():certCred_(0),
-                         peerVerificationEnabled_(false),
-                         logger_(LogFactory::getInstance())
+TLSContext::TLSContext()
+  : certCred_(0),
+    peerVerificationEnabled_(false)
 {
   int r = gnutls_certificate_allocate_credentials(&certCred_);
   if(r == GNUTLS_E_SUCCESS) {
@@ -56,8 +57,9 @@ TLSContext::TLSContext():certCred_(0),
                                         GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT);
   } else {
     good_ =false;
-    logger_->error("gnutls_certificate_allocate_credentials() failed."
-                   " Cause: %s", gnutls_strerror(r));
+    A2_LOG_ERROR(fmt("gnutls_certificate_allocate_credentials() failed."
+                     " Cause: %s",
+                     gnutls_strerror(r)));
   }
 }
 
@@ -86,14 +88,14 @@ bool TLSContext::addClientKeyFile(const std::string& certfile,
                                                  keyfile.c_str(),
                                                  GNUTLS_X509_FMT_PEM);
   if(ret == GNUTLS_E_SUCCESS) {
-    logger_->info("Client Key File(cert=%s, key=%s) were successfully added.",
-                  certfile.c_str(), keyfile.c_str());
+    A2_LOG_INFO(fmt("Client Key File(cert=%s, key=%s) were successfully added.",
+                    certfile.c_str(), keyfile.c_str()));
     return true;
   } else {
-    logger_->error("Failed to load client certificate from %s and"
-                   " private key from %s. Cause: %s",
-                   certfile.c_str(), keyfile.c_str(),
-                   gnutls_strerror(ret));
+    A2_LOG_ERROR(fmt("Failed to load client certificate from %s and"
+                     " private key from %s. Cause: %s",
+                     certfile.c_str(), keyfile.c_str(),
+                     gnutls_strerror(ret)));
     return false;
   }
 }
@@ -104,11 +106,11 @@ bool TLSContext::addTrustedCACertFile(const std::string& certfile)
                                                    certfile.c_str(),
                                                    GNUTLS_X509_FMT_PEM);
   if(ret < 0) {
-    logger_->error(MSG_LOADING_TRUSTED_CA_CERT_FAILED,
-                   certfile.c_str(), gnutls_strerror(ret));
+    A2_LOG_ERROR(fmt(MSG_LOADING_TRUSTED_CA_CERT_FAILED,
+                     certfile.c_str(), gnutls_strerror(ret)));
     return false;
   } else {
-    logger_->info("%d certificate(s) were imported.", ret);
+    A2_LOG_INFO(fmt("%d certificate(s) were imported.", ret));
     return true;
   }
 }
diff --git a/src/LibgnutlsTLSContext.h b/src/LibgnutlsTLSContext.h
index e3da322a..dd29cc69 100644
--- a/src/LibgnutlsTLSContext.h
+++ b/src/LibgnutlsTLSContext.h
@@ -45,8 +45,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class TLSContext {
 private:
   gnutls_certificate_credentials_t certCred_;
@@ -54,8 +52,6 @@ private:
   bool good_;
 
   bool peerVerificationEnabled_;
-
-  Logger* logger_;
 public:
   TLSContext();
 
diff --git a/src/LibsslTLSContext.cc b/src/LibsslTLSContext.cc
index 0bc84e8b..b3ff4d1f 100644
--- a/src/LibsslTLSContext.cc
+++ b/src/LibsslTLSContext.cc
@@ -39,21 +39,22 @@
 #include "LogFactory.h"
 #include "Logger.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "message.h"
 
 namespace aria2 {
 
-TLSContext::TLSContext():sslCtx_(0),
-                         peerVerificationEnabled_(false),
-                         logger_(LogFactory::getInstance())
+TLSContext::TLSContext()
+  : sslCtx_(0),
+    peerVerificationEnabled_(false)
 {
   sslCtx_ = SSL_CTX_new(SSLv23_client_method());
   if(sslCtx_) {
     good_ = true;
   } else {
     good_ = false;
-    logger_->error("SSL_CTX_new() failed. Cause: %s",
-                   ERR_error_string(ERR_get_error(), 0));
+    A2_LOG_ERROR(fmt("SSL_CTX_new() failed. Cause: %s",
+                     ERR_error_string(ERR_get_error(), 0)));
   }
   SSL_CTX_set_mode(sslCtx_, SSL_MODE_AUTO_RETRY);
 }
@@ -78,28 +79,32 @@ bool TLSContext::addClientKeyFile(const std::string& certfile,
 {
   if(SSL_CTX_use_PrivateKey_file(sslCtx_, keyfile.c_str(),
                                  SSL_FILETYPE_PEM) != 1) {
-    logger_->error("Failed to load client private key from %s. Cause: %s",
-                   keyfile.c_str(), ERR_error_string(ERR_get_error(), 0));
+    A2_LOG_ERROR(fmt("Failed to load client private key from %s. Cause: %s",
+                     keyfile.c_str(),
+                     ERR_error_string(ERR_get_error(), 0)));
     return false;
   }
   if(SSL_CTX_use_certificate_chain_file(sslCtx_, certfile.c_str()) != 1) {
-    logger_->error("Failed to load client certificate from %s. Cause: %s",
-                   certfile.c_str(), ERR_error_string(ERR_get_error(), 0));
+    A2_LOG_ERROR(fmt("Failed to load client certificate from %s. Cause: %s",
+                     certfile.c_str(),
+                     ERR_error_string(ERR_get_error(), 0)));
     return false;
   }
-  logger_->info("Client Key File(cert=%s, key=%s) were successfully added.",
-                certfile.c_str(), keyfile.c_str());
+  A2_LOG_INFO(fmt("Client Key File(cert=%s, key=%s) were successfully added.",
+                  certfile.c_str(),
+                  keyfile.c_str()));
   return true;
 }
 
 bool TLSContext::addTrustedCACertFile(const std::string& certfile)
 {
   if(SSL_CTX_load_verify_locations(sslCtx_, certfile.c_str(), 0) != 1) {
-    logger_->error(MSG_LOADING_TRUSTED_CA_CERT_FAILED,
-                   certfile.c_str(), ERR_error_string(ERR_get_error(), 0));
+    A2_LOG_ERROR(fmt(MSG_LOADING_TRUSTED_CA_CERT_FAILED,
+                     certfile.c_str(),
+                     ERR_error_string(ERR_get_error(), 0)));
     return false;
   } else {
-    logger_->info("Trusted CA certificates were successfully added.");
+    A2_LOG_INFO("Trusted CA certificates were successfully added.");
     return true;
   }
 }
diff --git a/src/LibsslTLSContext.h b/src/LibsslTLSContext.h
index 5262b7e9..66f361bb 100644
--- a/src/LibsslTLSContext.h
+++ b/src/LibsslTLSContext.h
@@ -45,8 +45,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class TLSContext {
 private:
   SSL_CTX* sslCtx_;
@@ -54,8 +52,6 @@ private:
   bool good_;
 
   bool peerVerificationEnabled_;
-
-  Logger* logger_;
 public:
   TLSContext();
 
diff --git a/src/LogFactory.cc b/src/LogFactory.cc
index d4008336..7df7623c 100644
--- a/src/LogFactory.cc
+++ b/src/LogFactory.cc
@@ -33,7 +33,6 @@
  */
 /* copyright --> */
 #include "LogFactory.h"
-#include "SimpleLogFormatter.h"
 #include "a2io.h"
 #include "prefs.h"
 #include "RecoverableException.h"
@@ -71,7 +70,6 @@ void LogFactory::reconfigure()
 Logger* LogFactory::getInstance() {
   if(!logger_) {
     Logger* slogger = new Logger();
-    slogger->setLogFormatter(new SimpleLogFormatter());
     try {
       openLogger(slogger);
     } catch(RecoverableException& e) {
diff --git a/src/LogFactory.h b/src/LogFactory.h
index 09a9942b..371a9dde 100644
--- a/src/LogFactory.h
+++ b/src/LogFactory.h
@@ -46,6 +46,7 @@ namespace aria2 {
 class LogFactory {
 private:
   static std::string filename_;
+  // TODO consider SharedHandle
   static Logger* logger_;
   static bool consoleOutput_;
   static Logger::LEVEL logLevel_;
diff --git a/src/Logger.cc b/src/Logger.cc
index de60f246..c931faef 100644
--- a/src/Logger.cc
+++ b/src/Logger.cc
@@ -2,7 +2,7 @@
 /*
  * aria2 - The high speed download utility
  *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ * Copyright (C) 2010 Tatsuhiro Tsujikawa
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -35,176 +35,187 @@
 #include "Logger.h"
 
 #include <cstring>
+#include <iostream>
 
 #include "DlAbortEx.h"
-#include "StringFormat.h"
+#include "fmt.h"
 #include "message.h"
-#include "LogFormatter.h"
+#include "A2STR.h"
+#include "a2time.h"
 
 namespace aria2 {
 
-const std::string Logger::DEBUG_LABEL("DEBUG");
+namespace {
+static const std::string DEBUG_LABEL("DEBUG");
 
-const std::string Logger::NOTICE_LABEL("NOTICE");
+static const std::string INFO_LABEL("INFO");
 
-const std::string Logger::WARN_LABEL("WARN");
+static const std::string NOTICE_LABEL("NOTICE");
 
-const std::string Logger::ERROR_LABEL("ERROR");
+static const std::string WARN_LABEL("WARN");
 
-const std::string Logger::INFO_LABEL("INFO");
+static const std::string ERROR_LABEL("ERROR");
+} // namespace
 
-Logger::Logger():
-  logFormatter_(0), logLevel_(Logger::A2_DEBUG), stdoutField_(0) {}
+Logger::Logger()
+  : logLevel_(Logger::A2_DEBUG),
+    stdoutField_(0)
+{}
 
 Logger::~Logger()
 {
   closeFile();
-  delete logFormatter_;
 }
 
 void Logger::openFile(const std::string& filename)
 {
   file_.open(filename.c_str(), std::ios::app|std::ios::binary);
   if(!file_) {
-    throw DL_ABORT_EX
-      (StringFormat(EX_FILE_OPEN, filename.c_str(), "n/a").str());
+    throw DL_ABORT_EX(fmt(EX_FILE_OPEN, filename.c_str(), "n/a"));
   }
 }
 
 void Logger::closeFile()
 {
+  std::cerr << "Closing log file" << std::endl;
+  // TODO Do we need file_.is_open()?
   if(file_.is_open()) {
     file_.close();
   }
 }
 
-#define WRITE_LOG(LEVEL, LEVEL_LABEL, MSG)              \
-  if(LEVEL >= logLevel_ && file_.is_open()) {           \
-    va_list ap;                                         \
-    va_start(ap, MSG);                                  \
-    writeLog(file_, LEVEL, LEVEL_LABEL, MSG, ap);       \
-    va_end(ap);                                         \
-    file_ << std::flush;                                \
-  }                                                     \
-  if(stdoutField_&LEVEL) {                              \
-    std::cout << "\n";                                  \
-    va_list ap;                                         \
-    va_start(ap, MSG);                                  \
-    writeLog(std::cout, LEVEL, LEVEL_LABEL, MSG, ap);   \
-    va_end(ap);                                         \
-    std::cout << std::flush;                            \
-  }                                                     \
-
-#define WRITE_LOG_EX(LEVEL, LEVEL_LABEL, MSG, EX)       \
-  if(LEVEL >= logLevel_ && file_.is_open()) {           \
-    va_list ap;                                         \
-    va_start(ap, EX);                                   \
-    writeLog(file_, LEVEL, LEVEL_LABEL, MSG, ap);       \
-    va_end(ap);                                         \
-    writeStackTrace(file_, LEVEL, LEVEL_LABEL, EX);     \
-    file_ << std::flush;                                \
-  }                                                     \
-  if(stdoutField_&LEVEL) {                              \
-    std::cout << "\n";                                  \
-    va_list ap;                                         \
-    va_start(ap, EX);                                   \
-    writeLog(std::cout, LEVEL, LEVEL_LABEL, MSG, ap);   \
-    va_end(ap);                                         \
-    writeStackTrace(std::cout, LEVEL, LEVEL_LABEL, EX); \
-    std::cout << std::flush;                            \
-  }                                                     \
-
-void Logger::debug(const char* msg, ...)
-{
-  WRITE_LOG(A2_DEBUG, DEBUG_LABEL, msg);
-}
-
-void Logger::debug(const char* msg, const Exception& ex, ...)
-{
-  WRITE_LOG_EX(A2_DEBUG, DEBUG_LABEL, msg, ex);
-}
-
-void Logger::info(const char* msg, ...)
-{
-  WRITE_LOG(A2_INFO, INFO_LABEL, msg);
-}
-
-void Logger::info(const char* msg, const Exception& ex, ...)
-{
-  WRITE_LOG_EX(A2_INFO, INFO_LABEL, msg, ex);
-}
-
-void Logger::notice(const char* msg, ...)
-{
-  WRITE_LOG(A2_NOTICE, NOTICE_LABEL, msg);
-}
-
-void Logger::notice(const char* msg, const Exception& ex, ...)
-{
-  WRITE_LOG_EX(A2_NOTICE, NOTICE_LABEL, msg, ex);
-}
-
-void Logger::warn(const char* msg, ...)
+void Logger::setStdoutLogLevel(Logger::LEVEL level, bool enabled)
 {
-  WRITE_LOG(A2_WARN, WARN_LABEL, msg);
+  if(enabled) {
+    stdoutField_ |= level;
+  } else {
+    stdoutField_ &= ~level;
+  }
 }
 
-void Logger::warn(const char* msg, const Exception& ex, ...)
+bool Logger::levelEnabled(LEVEL level)
 {
-  WRITE_LOG_EX(A2_WARN, WARN_LABEL, msg, ex);
+  return (level >= logLevel_ && file_.is_open()) || stdoutField_&level;
 }
 
-void Logger::error(const char*  msg, ...)
+namespace {
+const std::string& levelToString(Logger::LEVEL level)
 {
-  WRITE_LOG(A2_ERROR, ERROR_LABEL, msg);
+  switch(level) {
+  case Logger::A2_DEBUG:
+    return DEBUG_LABEL;
+  case Logger::A2_INFO:
+    return INFO_LABEL;
+  case Logger::A2_NOTICE:
+    return NOTICE_LABEL;
+  case Logger::A2_WARN:
+    return WARN_LABEL;
+  case Logger::A2_ERROR:
+    return ERROR_LABEL;
+  default:
+    return A2STR::NIL;
+  }
 }
-
-void Logger::error(const char* msg, const Exception& ex, ...)
-{
-  WRITE_LOG_EX(A2_ERROR, ERROR_LABEL, msg, ex);
+} // namespace
+
+namespace {
+void writeHeader
+(std::ostream& o, Logger::LEVEL level, const char* sourceFile, int lineNum)
+{
+  struct timeval tv;
+  gettimeofday(&tv, 0);
+  char datestr[27]; // 'YYYY-MM-DD hh:mm:ss.uuuuuu'+'\0' = 27 bytes
+  struct tm tm;
+  //tv.tv_sec may not be of type time_t.
+  time_t timesec = tv.tv_sec;
+  localtime_r(&timesec, &tm);
+  size_t dateLength =
+    strftime(datestr, sizeof(datestr), "%Y-%m-%d %H:%M:%S", &tm);
+  assert(dateLength <= (size_t)20);
+  snprintf(datestr+dateLength,
+           sizeof(datestr)-dateLength,
+           ".%06ld", tv.tv_usec);
+  o << datestr << " " << levelToString(level) << " - ";
+  if(sourceFile) {
+    o << "[" << sourceFile << ":" << lineNum << "] ";
+  }
 }
+} // namespace
 
-void Logger::setLogFormatter(LogFormatter* logFormatter)
+namespace {
+void writeStackTrace(std::ostream& o, const std::string& stackTrace)
 {
-  delete logFormatter_;
-  logFormatter_ = logFormatter;
+  o << stackTrace;
 }
+} // namespace
 
-void Logger::setStdoutLogLevel(Logger::LEVEL level, bool enabled)
+namespace {
+void writeLog
+(std::ostream& o,
+ Logger::LEVEL level,
+ const char* sourceFile,
+ int lineNum,
+ const char* msg,
+ const std::string& trace,
+ bool toStream,
+ bool toConsole)
 {
-  if(enabled) {
-    stdoutField_ |= level;
-  } else {
-    stdoutField_ &= ~level;
+  if(toStream) {
+    writeHeader(o, level, sourceFile, lineNum);
+    o << msg << "\n";
+    writeStackTrace(o, trace);
+    o << std::flush;
+  }
+  if(toConsole) {
+    std::cout << "\n";
+    writeHeader(std::cout, level, 0, 0);
+    std::cout << msg << "\n";
+    writeStackTrace(std::cout, trace);
+    std::cout << std::flush;
   }
 }
+} // namespace
 
-void Logger::writeLog
-(std::ostream& o, LEVEL logLevel, const std::string& logLevelLabel,
- const char* msg, va_list ap)
+void Logger::log
+(LEVEL level,
+ const char* sourceFile,
+ int lineNum,
+ const char* msg)
 {
-  if(logFormatter_) {
-    logFormatter_->writeLog(o, logLevel, logLevelLabel, msg, ap);
-  }
+  writeLog(file_, level, sourceFile, lineNum, msg, A2STR::NIL,
+           level >= logLevel_ && file_.is_open(),
+           stdoutField_&level);
 }
 
-void Logger::writeStackTrace
-(std::ostream& o, LEVEL logLevel, const std::string& logLevelLabel,
- const Exception& ex)
+void Logger::log
+(LEVEL level,
+ const char* sourceFile,
+ int lineNum,
+ const std::string& msg)
 {
-  if(logFormatter_) {
-    logFormatter_->writeStackTrace(o, logLevel, logLevelLabel, ex);
-  }
+  log(level, sourceFile, lineNum, msg.c_str());
 }
 
-bool Logger::debug()
+void Logger::log
+(LEVEL level,
+ const char* sourceFile,
+ int lineNum,
+ const char* msg,
+ const Exception& ex)
 {
-  return levelEnabled(A2_DEBUG);
+  writeLog(file_, level, sourceFile, lineNum, msg, ex.stackTrace(),
+           level >= logLevel_ && file_.is_open(),
+           stdoutField_&level);
 }
 
-bool Logger::info()
+void Logger::log
+(LEVEL level,
+ const char* sourceFile,
+ int lineNum,
+ const std::string& msg,
+ const Exception& ex)
 {
-  return levelEnabled(A2_INFO);
+  log(level, sourceFile, lineNum, msg.c_str(), ex);
 }
 
 } // namespace aria2
diff --git a/src/Logger.h b/src/Logger.h
index af032453..6dee4851 100644
--- a/src/Logger.h
+++ b/src/Logger.h
@@ -2,7 +2,7 @@
 /*
  * aria2 - The high speed download utility
  *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ * Copyright (C) 2010 Tatsuhiro Tsujikawa
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -37,15 +37,12 @@
 
 #include "common.h"
 
-#include <cstdarg>
 #include <string>
 #include <fstream>
-#include <iostream>
 
 namespace aria2 {
 
 class Exception;
-class LogFormatter;
 
 class Logger {
 public:
@@ -56,78 +53,45 @@ public:
     A2_WARN   = 1 << 3,
     A2_ERROR  = 1 << 4,
   };
-
-  static const std::string DEBUG_LABEL;
-
-  static const std::string NOTICE_LABEL;
-
-  static const std::string WARN_LABEL;
-
-  static const std::string ERROR_LABEL;
-
-  static const std::string INFO_LABEL;
 private:
-  LogFormatter* logFormatter_;
-
   LEVEL logLevel_;
-
   std::ofstream file_;
-
-  int stdoutField_;
-  
-  bool levelEnabled(LEVEL level)
-  {
-    return (level >= logLevel_ && file_.is_open()) || stdoutField_&level;
-  }
-
-  void writeLog
-  (std::ostream& o, LEVEL logLevel, const std::string& logLevelLabel,
-   const char* msg, va_list ap);
-
-  void writeStackTrace
-  (std::ostream& o, LEVEL logLevel, const std::string& logLevelLabel,
-   const Exception& ex);
+  int stdoutField_;  
 public:
   Logger();
 
-  virtual ~Logger();
-
-  void debug(const char* msg, ...)
-    __attribute__ ((format (printf, 2, 3)));
-
-  void debug(const char* msg, const Exception& ex, ...)
-    __attribute__ ((format (printf, 2, 4)));
-
-  void info(const char* msg, ...)
-    __attribute__ ((format (printf, 2, 3)));
-
-  void info(const char* msg, const Exception& ex, ...)
-    __attribute__ ((format (printf, 2, 4)));
-
-  void notice(const char* msg, ...)
-    __attribute__ ((format (printf, 2, 3)));
-
-  void notice(const char* msg, const Exception& ex, ...)
-    __attribute__ ((format (printf, 2, 4)));
-
-  void warn(const char* msg, ...)
-    __attribute__ ((format (printf, 2, 3)));
-
-  void warn(const char* msg, const Exception& ex, ...)
-    __attribute__ ((format (printf, 2, 4)));
-
-  void error(const char*  msg, ...)
-    __attribute__ ((format (printf, 2, 3)));
+  ~Logger();
+
+  void log
+  (LEVEL level,
+   const char* sourceFile,
+   int lineNum,
+   const char* msg);
+
+  void log
+  (LEVEL level,
+   const char* sourceFile,
+   int lineNum,
+   const std::string& msg);
+
+  void log
+  (LEVEL level,
+   const char* sourceFile,
+   int lineNum,
+   const char* msg,
+   const Exception& ex);
 
-  void error(const char* msg, const Exception& ex, ...)
-    __attribute__ ((format (printf, 2, 4)));
+  void log
+  (LEVEL level,
+   const char* sourceFile,
+   int lineNum,
+   const std::string& msg,
+   const Exception& ex);
 
   void openFile(const std::string& filename);
 
   void closeFile();
 
-  void setLogFormatter(LogFormatter* logFormatter);
-
   void setLogLevel(LEVEL level)
   {
     logLevel_ = level;
@@ -137,11 +101,73 @@ public:
 
   // Returns true if this logger actually writes debug log message to
   // either file or stdout.
-  bool debug();
-
-  bool info();
+  bool levelEnabled(LEVEL level);
 };
 
+#define A2_LOG_DEBUG_ENABLED                                            \
+  aria2::LogFactory::getInstance()->levelEnabled(Logger::A2_DEBUG)
+
+#define A2_LOG_DEBUG(msg)                                               \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_DEBUG))                          \
+      logger->log(Logger::A2_DEBUG, __FILE__, __LINE__, msg);           \
+  }
+#define A2_LOG_DEBUG_EX(msg, ex)                                        \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_DEBUG))                          \
+      logger->log(Logger::A2_DEBUG, __FILE__, __LINE__, msg, ex);      \
+  }
+#define A2_LOG_INFO(msg)                                                \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_INFO))                           \
+      logger->log(Logger::A2_INFO, __FILE__, __LINE__, msg);            \
+  }
+#define A2_LOG_INFO_EX(msg, ex)                                         \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_INFO))                           \
+      logger->log(Logger::A2_INFO, __FILE__, __LINE__, msg, ex);       \
+  }
+#define A2_LOG_NOTICE(msg)                                              \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_NOTICE))                         \
+      logger->log(Logger::A2_NOTICE, __FILE__, __LINE__, msg);          \
+  }
+#define A2_LOG_NOTICE_EX(msg, ex)                                       \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_NOTICE))                         \
+      logger->log(Logger::A2_NOTICE, __FILE__, __LINE__, msg, ex);     \
+  }
+#define A2_LOG_WARN(msg)                                                \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_WARN))                           \
+      logger->log(Logger::A2_WARN, __FILE__, __LINE__, msg);            \
+  }
+#define A2_LOG_WARN_EX(msg, ex)                                         \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_WARN))                           \
+      logger->log(Logger::A2_WARN, __FILE__, __LINE__, msg, ex);        \
+  }
+#define A2_LOG_ERROR(msg)                                               \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_ERROR))                          \
+      logger->log(Logger::A2_ERROR, __FILE__, __LINE__, msg);           \
+  }
+#define A2_LOG_ERROR_EX(msg, ex)                                        \
+  {                                                                     \
+    aria2::Logger* logger = aria2::LogFactory::getInstance();           \
+    if(logger->levelEnabled(Logger::A2_ERROR))                          \
+      logger->log(Logger::A2_ERROR, __FILE__, __LINE__, msg, ex);      \
+  }
+
 } // namespace aria2
 
 #endif // D_LOGGER_H
diff --git a/src/LpdDispatchMessageCommand.cc b/src/LpdDispatchMessageCommand.cc
index a6044a12..00c74808 100644
--- a/src/LpdDispatchMessageCommand.cc
+++ b/src/LpdDispatchMessageCommand.cc
@@ -37,20 +37,23 @@
 #include "DownloadEngine.h"
 #include "BtRuntime.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "RecoverableException.h"
 #include "SocketCore.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 LpdDispatchMessageCommand::LpdDispatchMessageCommand
 (cuid_t cuid,
  const SharedHandle<LpdMessageDispatcher>& dispatcher,
- DownloadEngine* e):
-  Command(cuid),
-  dispatcher_(dispatcher),
-  e_(e),
-  tryCount_(0) {}
+ DownloadEngine* e)
+  : Command(cuid),
+    dispatcher_(dispatcher),
+    e_(e),
+    tryCount_(0)
+{}
 
 LpdDispatchMessageCommand::~LpdDispatchMessageCommand() {}
 
@@ -61,25 +64,25 @@ bool LpdDispatchMessageCommand::execute()
   }
   if(dispatcher_->isAnnounceReady()) {
     try {
-      getLogger()->info("Dispatching LPD message for infohash=%s",
-                   util::toHex(dispatcher_->getInfoHash()).c_str());
+      A2_LOG_INFO(fmt("Dispatching LPD message for infohash=%s",
+                      util::toHex(dispatcher_->getInfoHash()).c_str()));
       if(dispatcher_->sendMessage()) {
-        getLogger()->info("Sending LPD message is complete.");
+        A2_LOG_INFO("Sending LPD message is complete.");
         dispatcher_->resetAnnounceTimer();
         tryCount_ = 0;
       } else {
         ++tryCount_;
         if(tryCount_ >= 5) {
-          getLogger()->info("Sending LPD message %u times but all failed.",
-                            tryCount_);
+          A2_LOG_INFO(fmt("Sending LPD message %u times but all failed.",
+                          tryCount_));
           dispatcher_->resetAnnounceTimer();
           tryCount_ = 0;
         } else {
-          getLogger()->info("Could not send LPD message, retry shortly.");
+          A2_LOG_INFO("Could not send LPD message, retry shortly.");
         }
       }
     } catch(RecoverableException& e) {
-      getLogger()->info("Failed to send LPD message.", e);
+      A2_LOG_INFO_EX("Failed to send LPD message.", e);
       dispatcher_->resetAnnounceTimer();
       tryCount_ = 0;
     }
diff --git a/src/LpdMessageDispatcher.cc b/src/LpdMessageDispatcher.cc
index 629e5dff..ba2bbdf7 100644
--- a/src/LpdMessageDispatcher.cc
+++ b/src/LpdMessageDispatcher.cc
@@ -39,22 +39,25 @@
 #include "BtConstants.h"
 #include "RecoverableException.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 LpdMessageDispatcher::LpdMessageDispatcher
-(const std::string& infoHash, uint16_t port,
- const std::string& multicastAddress, uint16_t multicastPort,
- time_t interval):
-  infoHash_(infoHash),
-  port_(port),
-  multicastAddress_(multicastAddress),
-  multicastPort_(multicastPort),
-  timer_(0),
-  interval_(interval),
-  request_(bittorrent::createLpdRequest(multicastAddress_, multicastPort_,
-                                        infoHash_, port_)),
-  logger_(LogFactory::getInstance()) {}
+(const std::string& infoHash,
+ uint16_t port,
+ const std::string& multicastAddress,
+ uint16_t multicastPort,
+ time_t interval)
+  : infoHash_(infoHash),
+    port_(port),
+    multicastAddress_(multicastAddress),
+    multicastPort_(multicastPort),
+    timer_(0),
+    interval_(interval),
+    request_(bittorrent::createLpdRequest(multicastAddress_, multicastPort_,
+                                          infoHash_, port_))
+{}
 
 LpdMessageDispatcher::~LpdMessageDispatcher() {}
 
@@ -64,23 +67,18 @@ bool LpdMessageDispatcher::init(const std::string& localAddr,
   try {
     socket_.reset(new SocketCore(SOCK_DGRAM));
     socket_->create(AF_INET);
-    if(logger_->debug()) {
-      logger_->debug("Setting multicast outgoing interface=%s",
-                     localAddr.c_str());
-    }
+    A2_LOG_DEBUG(fmt("Setting multicast outgoing interface=%s",
+                     localAddr.c_str()));
     socket_->setMulticastInterface(localAddr);
-    if(logger_->debug()) {
-      logger_->debug("Setting multicast ttl=%u",static_cast<unsigned int>(ttl));
-    }
+    A2_LOG_DEBUG(fmt("Setting multicast ttl=%u",
+                     static_cast<unsigned int>(ttl)));
     socket_->setMulticastTtl(ttl);
-    if(logger_->debug()) {
-      logger_->debug("Setting multicast loop=%u",
-                     static_cast<unsigned int>(loop));
-    }
+    A2_LOG_DEBUG(fmt("Setting multicast loop=%u",
+                     static_cast<unsigned int>(loop)));
     socket_->setMulticastLoop(loop);
     return true;
   } catch(RecoverableException& e) {
-    logger_->error("Failed to initialize LpdMessageDispatcher.", e);
+    A2_LOG_ERROR_EX("Failed to initialize LpdMessageDispatcher.", e);
   }
   return false;
 }
diff --git a/src/LpdMessageDispatcher.h b/src/LpdMessageDispatcher.h
index edfee452..e4685416 100644
--- a/src/LpdMessageDispatcher.h
+++ b/src/LpdMessageDispatcher.h
@@ -43,7 +43,6 @@
 namespace aria2 {
 
 class SocketCore;
-class Logger;
 
 class LpdMessageDispatcher {
 private:
@@ -55,7 +54,6 @@ private:
   Timer timer_;
   time_t interval_;
   std::string request_;
-  Logger* logger_;
 public:
   LpdMessageDispatcher
   (const std::string& infoHash, uint16_t port,
diff --git a/src/LpdMessageReceiver.cc b/src/LpdMessageReceiver.cc
index 1c6db0a0..f5fd290c 100644
--- a/src/LpdMessageReceiver.cc
+++ b/src/LpdMessageReceiver.cc
@@ -40,14 +40,15 @@
 #include "LpdMessage.h"
 #include "RecoverableException.h"
 #include "Peer.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 LpdMessageReceiver::LpdMessageReceiver
-(const std::string& multicastAddress, uint16_t multicastPort):
-  multicastAddress_(multicastAddress),
-  multicastPort_(multicastPort),
-  logger_(LogFactory::getInstance()) {}
+(const std::string& multicastAddress, uint16_t multicastPort)
+  : multicastAddress_(multicastAddress),
+    multicastPort_(multicastPort)
+{}
 
 LpdMessageReceiver::~LpdMessageReceiver() {}
 
@@ -61,19 +62,17 @@ bool LpdMessageReceiver::init(const std::string& localAddr)
 #else // !__MINGW32__
     socket_->bind(multicastAddress_, multicastPort_, AF_INET);
 #endif // !__MINGW32__
-    if(logger_->debug()) {
-      logger_->debug("Joining multicast group. %s:%u, localAddr=%s",
+    A2_LOG_DEBUG(fmt("Joining multicast group. %s:%u, localAddr=%s",
                      multicastAddress_.c_str(), multicastPort_,
-                     localAddr.c_str());
-    }
+                     localAddr.c_str()));
     socket_->joinMulticastGroup(multicastAddress_, multicastPort_, localAddr);
     socket_->setNonBlockingMode();
     localAddress_ = localAddr;
-    logger_->info("Listening multicast group (%s:%u) packet",
-                  multicastAddress_.c_str(), multicastPort_);
+    A2_LOG_INFO(fmt("Listening multicast group (%s:%u) packet",
+                    multicastAddress_.c_str(), multicastPort_));
     return true;
   } catch(RecoverableException& e) {
-    logger_->error("Failed to initialize LPD message receiver.", e);
+    A2_LOG_ERROR_EX("Failed to initialize LPD message receiver.", e);
   }
   return false;
 }
@@ -97,13 +96,15 @@ SharedHandle<LpdMessage> LpdMessageReceiver::receiveMessage()
     SharedHandle<HttpHeader> header = proc.getHttpRequestHeader();
     std::string infoHashString = header->getFirst("Infohash");
     uint16_t port = header->getFirstAsUInt("Port");
-    logger_->info("LPD message received infohash=%s, port=%u from %s",
-                  infoHashString.c_str(), port, peerAddr.first.c_str());
+    A2_LOG_INFO(fmt("LPD message received infohash=%s, port=%u from %s",
+                    infoHashString.c_str(),
+                    port,
+                    peerAddr.first.c_str()));
     std::string infoHash;
     if(infoHashString.size() != 40 ||
        (infoHash = util::fromHex(infoHashString)).empty() ||
        port == 0) {
-      logger_->info("LPD bad request. infohash=%s", infoHashString.c_str());
+      A2_LOG_INFO(fmt("LPD bad request. infohash=%s", infoHashString.c_str()));
       msg.reset(new LpdMessage());
       return msg;
     }
@@ -114,7 +115,7 @@ SharedHandle<LpdMessage> LpdMessageReceiver::receiveMessage()
     msg.reset(new LpdMessage(peer, infoHash));
     return msg;
   } catch(RecoverableException& e) {
-    logger_->info("Failed to receive LPD message.", e);
+    A2_LOG_INFO_EX("Failed to receive LPD message.", e);
     msg.reset(new LpdMessage());
     return msg;
   }
diff --git a/src/LpdMessageReceiver.h b/src/LpdMessageReceiver.h
index 2cff5700..757d9800 100644
--- a/src/LpdMessageReceiver.h
+++ b/src/LpdMessageReceiver.h
@@ -42,7 +42,6 @@
 namespace aria2 {
 
 class SocketCore;
-class Logger;
 class LpdMessage;
 
 class LpdMessageReceiver {
@@ -51,7 +50,6 @@ private:
   std::string multicastAddress_;
   uint16_t multicastPort_;
   std::string localAddress_;
-  Logger* logger_;
 public:
   // Currently only IPv4 multicastAddresses are supported.
   LpdMessageReceiver
diff --git a/src/LpdReceiveMessageCommand.cc b/src/LpdReceiveMessageCommand.cc
index 594fa16a..741c6033 100644
--- a/src/LpdReceiveMessageCommand.cc
+++ b/src/LpdReceiveMessageCommand.cc
@@ -43,9 +43,11 @@
 #include "RequestGroup.h"
 #include "BtRegistry.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "LpdMessage.h"
 #include "bittorrent_helper.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -54,8 +56,12 @@ unsigned int LpdReceiveMessageCommand::numInstance_ = 0;
 LpdReceiveMessageCommand* LpdReceiveMessageCommand::instance_ = 0;
 
 LpdReceiveMessageCommand::LpdReceiveMessageCommand
-(cuid_t cuid, const SharedHandle<LpdMessageReceiver>& receiver,
- DownloadEngine* e):Command(cuid), receiver_(receiver), e_(e)
+(cuid_t cuid,
+ const SharedHandle<LpdMessageReceiver>& receiver,
+ DownloadEngine* e)
+  : Command(cuid),
+    receiver_(receiver),
+    e_(e)
 {
   e_->addSocketForReadCheck(receiver_->getSocket(), this);
   ++numInstance_;
@@ -88,17 +94,12 @@ bool LpdReceiveMessageCommand::execute()
     SharedHandle<DownloadContext> dctx =
       reg->getDownloadContext(m->getInfoHash());
     if(!dctx) {
-      if(getLogger()->debug()) {
-        getLogger()->debug("Download Context is null for infohash=%s.",
-                           util::toHex(m->getInfoHash()).c_str());
-      }
+      A2_LOG_DEBUG(fmt("Download Context is null for infohash=%s.",
+                       util::toHex(m->getInfoHash()).c_str()));
       continue;
     }
     if(bittorrent::getTorrentAttrs(dctx)->privateTorrent) {
-      if(getLogger()->debug()) {
-        getLogger()->debug
-          ("Ignore LPD message because the torrent is private.");
-      }
+      A2_LOG_DEBUG("Ignore LPD message because the torrent is private.");
       continue;
     }
     RequestGroup* group = dctx->getOwnerRequestGroup();
@@ -109,17 +110,13 @@ bool LpdReceiveMessageCommand::execute()
     assert(peerStorage);
     SharedHandle<Peer> peer = m->getPeer();
     if(peerStorage->addPeer(peer)) {
-      if(getLogger()->debug()) {
-        getLogger()->debug("LPD peer %s:%u local=%d added.",
-                           peer->getIPAddress().c_str(), peer->getPort(),
-                           peer->isLocalPeer()?1:0);
-      }
+      A2_LOG_DEBUG(fmt("LPD peer %s:%u local=%d added.",
+                       peer->getIPAddress().c_str(), peer->getPort(),
+                       peer->isLocalPeer()?1:0));
     } else {
-      if(getLogger()->debug()) {
-        getLogger()->debug("LPD peer %s:%u local=%d not added.",
-                           peer->getIPAddress().c_str(), peer->getPort(),
-                           peer->isLocalPeer()?1:0);
-      }
+      A2_LOG_DEBUG(fmt("LPD peer %s:%u local=%d not added.",
+                       peer->getIPAddress().c_str(), peer->getPort(),
+                       peer->isLocalPeer()?1:0));
     }
   }
   e_->addCommand(this);
diff --git a/src/MSEHandshake.cc b/src/MSEHandshake.cc
index 0ae9c6b5..5eb35b37 100644
--- a/src/MSEHandshake.cc
+++ b/src/MSEHandshake.cc
@@ -55,6 +55,7 @@
 #include "prefs.h"
 #include "Option.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "bittorrent_helper.h"
 
 namespace aria2 {
@@ -65,23 +66,23 @@ const unsigned char* MSEHandshake::GENERATOR = reinterpret_cast<const unsigned c
 
 const unsigned char MSEHandshake::VC[] = { 0, 0, 0, 0, 0, 0, 0, 0 };
 
-MSEHandshake::MSEHandshake(cuid_t cuid,
-                           const SocketHandle& socket,
-                           const Option* op):
-  cuid_(cuid),
-  socket_(socket),
-  option_(op),
-  logger_(LogFactory::getInstance()),
-  rbufLength_(0),
-  socketBuffer_(socket),
-  negotiatedCryptoType_(CRYPTO_NONE),
-  dh_(0),
-  initiator_(true),
-  markerIndex_(0),
-  padLength_(0),
-  iaLength_(0),
-  ia_(0),
-  sha1_(MessageDigest::sha1())
+MSEHandshake::MSEHandshake
+(cuid_t cuid,
+ const SocketHandle& socket,
+ const Option* op)
+  : cuid_(cuid),
+    socket_(socket),
+    option_(op),
+    rbufLength_(0),
+    socketBuffer_(socket),
+    negotiatedCryptoType_(CRYPTO_NONE),
+    dh_(0),
+    initiator_(true),
+    markerIndex_(0),
+    padLength_(0),
+    iaLength_(0),
+    ia_(0),
+    sha1_(MessageDigest::sha1())
 {}
 
 MSEHandshake::~MSEHandshake()
@@ -106,16 +107,12 @@ MSEHandshake::HANDSHAKE_TYPE MSEHandshake::identifyHandshakeType()
   }
   if(rbuf_[0] == BtHandshakeMessage::PSTR_LENGTH &&
      memcmp(BtHandshakeMessage::BT_PSTR, rbuf_+1, 19) == 0) {
-    if(logger_->debug()) {
-      logger_->debug("CUID#%s - This is legacy BitTorrent handshake.",
-                     util::itos(cuid_).c_str());
-    }
+    A2_LOG_DEBUG(fmt("CUID#%s - This is legacy BitTorrent handshake.",
+                     util::itos(cuid_).c_str()));
     return HANDSHAKE_LEGACY;
   } else {
-    if(logger_->debug()) {
-      logger_->debug("CUID#%s - This may be encrypted BitTorrent handshake.",
-                     util::itos(cuid_).c_str());
-    }
+    A2_LOG_DEBUG(fmt("CUID#%s - This may be encrypted BitTorrent handshake.",
+                     util::itos(cuid_).c_str()));
     return HANDSHAKE_ENCRYPTED;
   }
 }
@@ -126,19 +123,15 @@ void MSEHandshake::initEncryptionFacility(bool initiator)
   dh_ = new DHKeyExchange();
   dh_->init(PRIME, PRIME_BITS, GENERATOR, 160);
   dh_->generatePublicKey();
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - DH initialized.", util::itos(cuid_).c_str());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - DH initialized.", util::itos(cuid_).c_str()));
   initiator_ = initiator;
 }
 
 bool MSEHandshake::sendPublicKey()
 {
   if(socketBuffer_.sendBufferIsEmpty()) {
-    if(logger_->debug()) {
-      logger_->debug("CUID#%s - Sending public key.",
-                     util::itos(cuid_).c_str());
-    }
+    A2_LOG_DEBUG(fmt("CUID#%s - Sending public key.",
+                     util::itos(cuid_).c_str()));
     unsigned char buffer[KEY_LENGTH+MAX_PAD_LENGTH];
     dh_->getPublicKey(buffer, KEY_LENGTH);
 
@@ -157,9 +150,8 @@ bool MSEHandshake::receivePublicKey()
   if(r > receiveNBytes(r)) {
     return false;
   }
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - public key received.", util::itos(cuid_).c_str());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - public key received.",
+                   util::itos(cuid_).c_str()));
   // TODO handle exception. in catch, resbufLength = 0;
   dh_->computeSecret(secret_, sizeof(secret_), rbuf_, rbufLength_);
   // reset rbufLength_
@@ -263,10 +255,8 @@ uint16_t MSEHandshake::decodeLength16(const unsigned char* buffer)
 bool MSEHandshake::sendInitiatorStep2()
 {
   if(socketBuffer_.sendBufferIsEmpty()) {
-    if(logger_->debug()) {
-      logger_->debug("CUID#%s - Sending negotiation step2.",
-                     util::itos(cuid_).c_str());
-    }
+    A2_LOG_DEBUG(fmt("CUID#%s - Sending negotiation step2.",
+                     util::itos(cuid_).c_str()));
     unsigned char md[20];
     createReq1Hash(md);
     socketBuffer_.pushStr(std::string(&md[0], &md[sizeof(md)]));
@@ -352,11 +342,9 @@ bool MSEHandshake::findInitiatorVCMarker()
   size_t toRead = markerIndex_+VC_LENGTH-rbufLength_;
   socket_->readData(rbuf_+rbufLength_, toRead);
   rbufLength_ += toRead;
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - VC marker found at %lu",
+  A2_LOG_DEBUG(fmt("CUID#%s - VC marker found at %lu",
                    util::itos(cuid_).c_str(),
-                   static_cast<unsigned long>(markerIndex_));
-  }
+                   static_cast<unsigned long>(markerIndex_)));
   verifyVC(rbuf_+markerIndex_);
   // reset rbufLength_
   rbufLength_ = 0;
@@ -377,17 +365,13 @@ bool MSEHandshake::receiveInitiatorCryptoSelectAndPadDLength()
                         rbufptr, sizeof(cryptoSelect));
     if(cryptoSelect[3]&CRYPTO_PLAIN_TEXT &&
        option_->get(PREF_BT_MIN_CRYPTO_LEVEL) == V_PLAIN) {
-      if(logger_->debug()) {
-        logger_->debug("CUID#%s - peer prefers plaintext.",
-                       util::itos(cuid_).c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - peer prefers plaintext.",
+                       util::itos(cuid_).c_str()));
       negotiatedCryptoType_ = CRYPTO_PLAIN_TEXT;
     }
     if(cryptoSelect[3]&CRYPTO_ARC4) {
-      if(logger_->debug()) {
-        logger_->debug("CUID#%s - peer prefers ARC4",
-                       util::itos(cuid_).c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - peer prefers ARC4",
+                       util::itos(cuid_).c_str()));
       negotiatedCryptoType_ = CRYPTO_ARC4;
     }
     if(negotiatedCryptoType_ == CRYPTO_NONE) {
@@ -454,11 +438,9 @@ bool MSEHandshake::findReceiverHashMarker()
   size_t toRead = markerIndex_+20-rbufLength_;
   socket_->readData(rbuf_+rbufLength_, toRead);
   rbufLength_ += toRead;
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - Hash marker found at %lu.",
+  A2_LOG_DEBUG(fmt("CUID#%s - Hash marker found at %lu.",
                    util::itos(cuid_).c_str(),
-                   static_cast<unsigned long>(markerIndex_));
-  }
+                   static_cast<unsigned long>(markerIndex_)));
   verifyReq1Hash(rbuf_+markerIndex_);
   // reset rbufLength_
   rbufLength_ = 0;
@@ -483,11 +465,9 @@ bool MSEHandshake::receiveReceiverHashAndPadCLength
     const unsigned char* infohash = bittorrent::getInfoHash(*i);
     createReq23Hash(md, infohash);
     if(memcmp(md, rbufptr, sizeof(md)) == 0) {
-      if(logger_->debug()) {
-        logger_->debug("CUID#%s - info hash found: %s",
+      A2_LOG_DEBUG(fmt("CUID#%s - info hash found: %s",
                        util::itos(cuid_).c_str(),
-                       util::toHex(infohash, INFO_HASH_LENGTH).c_str());
-      }
+                       util::toHex(infohash, INFO_HASH_LENGTH).c_str()));
       downloadContext = *i;
       break;
     }
@@ -509,16 +489,12 @@ bool MSEHandshake::receiveReceiverHashAndPadCLength
     // For now, choose ARC4.
     if(cryptoProvide[3]&CRYPTO_PLAIN_TEXT &&
        option_->get(PREF_BT_MIN_CRYPTO_LEVEL) == V_PLAIN) {
-      if(logger_->debug()) {
-        logger_->debug("CUID#%s - peer provides plaintext.",
-                       util::itos(cuid_).c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - peer provides plaintext.",
+                       util::itos(cuid_).c_str()));
       negotiatedCryptoType_ = CRYPTO_PLAIN_TEXT;
     } else if(cryptoProvide[3]&CRYPTO_ARC4) {
-      if(logger_->debug()) {
-        logger_->debug("CUID#%s - peer provides ARC4.",
-                       util::itos(cuid_).c_str());
-      }
+      A2_LOG_DEBUG(fmt("CUID#%s - peer provides ARC4.",
+                       util::itos(cuid_).c_str()));
       negotiatedCryptoType_ = CRYPTO_ARC4;
     }
     if(negotiatedCryptoType_ == CRYPTO_NONE) {
@@ -543,10 +519,8 @@ bool MSEHandshake::receiveReceiverIALength()
     return false;
   }
   iaLength_ = decodeLength16(rbuf_);
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - len(IA)=%u.",
-                   util::itos(cuid_).c_str(), iaLength_);
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - len(IA)=%u.",
+                   util::itos(cuid_).c_str(), iaLength_));
   // reset rbufLength_
   rbufLength_ = 0;
   return true;
@@ -564,9 +538,7 @@ bool MSEHandshake::receiveReceiverIA()
   delete [] ia_;
   ia_ = new unsigned char[iaLength_];
   decryptor_->decrypt(ia_, iaLength_, rbuf_, iaLength_);
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - IA received.", util::itos(cuid_).c_str());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - IA received.", util::itos(cuid_).c_str()));
   // reset rbufLength_
   rbufLength_ = 0;
   return true;
@@ -605,15 +577,11 @@ bool MSEHandshake::sendReceiverStep2()
 
 uint16_t MSEHandshake::verifyPadLength(const unsigned char* padlenbuf, const char* padName)
 {
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - Verifying Pad length for %s",
-                   util::itos(cuid_).c_str(), padName);
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - Verifying Pad length for %s",
+                   util::itos(cuid_).c_str(), padName));
   uint16_t padLength = decodeLength16(padlenbuf);
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - len(%s)=%u",
-                   util::itos(cuid_).c_str(), padName, padLength);
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - len(%s)=%u",
+                   util::itos(cuid_).c_str(), padName, padLength));
   if(padLength > 512) {
     throw DL_ABORT_EX
       (StringFormat("Too large %s length: %u", padName, padLength).str());
@@ -623,9 +591,7 @@ uint16_t MSEHandshake::verifyPadLength(const unsigned char* padlenbuf, const cha
 
 void MSEHandshake::verifyVC(const unsigned char* vcbuf)
 {
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - Verifying VC.", util::itos(cuid_).c_str());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - Verifying VC.", util::itos(cuid_).c_str()));
   unsigned char vc[VC_LENGTH];
   decryptor_->decrypt(vc, sizeof(vc), vcbuf, sizeof(vc));
   if(memcmp(VC, vc, sizeof(VC)) != 0) {
@@ -636,9 +602,7 @@ void MSEHandshake::verifyVC(const unsigned char* vcbuf)
 
 void MSEHandshake::verifyReq1Hash(const unsigned char* req1buf)
 {
-  if(logger_->debug()) {
-    logger_->debug("CUID#%s - Verifying req hash.", util::itos(cuid_).c_str());
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s - Verifying req hash.", util::itos(cuid_).c_str()));
   unsigned char md[20];
   createReq1Hash(md);
   if(memcmp(md, req1buf, sizeof(md)) != 0) {
diff --git a/src/MSEHandshake.h b/src/MSEHandshake.h
index 7cb988c9..4e22d407 100644
--- a/src/MSEHandshake.h
+++ b/src/MSEHandshake.h
@@ -47,7 +47,6 @@
 namespace aria2 {
 
 class Option;
-class Logger;
 class SocketCore;
 class DHKeyExchange;
 class ARC4Encryptor;
@@ -85,7 +84,6 @@ private:
   cuid_t cuid_;
   SharedHandle<SocketCore> socket_;
   const Option* option_;
-  Logger* logger_;
 
   unsigned char rbuf_[MAX_BUFFER_LENGTH];
   size_t rbufLength_;
diff --git a/src/Makefile.am b/src/Makefile.am
index 84f16a77..bc172c8f 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -40,8 +40,7 @@ SRCS =  Socket.h\
 	DlRetryEx.cc DlRetryEx.h\
 	DownloadFailureException.cc DownloadFailureException.h\
 	Logger.cc Logger.h\
-	LogFormatter.h\
-	SimpleLogFormatter.cc SimpleLogFormatter.h\
+	fmt.cc fmt.h\
 	DiskWriter.h\
 	DiskWriterFactory.h\
 	AbstractDiskWriter.cc AbstractDiskWriter.h\
diff --git a/src/Makefile.in b/src/Makefile.in
index 3f399dc9..6ae33d66 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -351,10 +351,9 @@ am__libaria2c_a_SOURCES_DIST = Socket.h SocketCore.cc SocketCore.h \
 	FatalException.h RecoverableException.cc \
 	RecoverableException.h DlAbortEx.cc DlAbortEx.h DlRetryEx.cc \
 	DlRetryEx.h DownloadFailureException.cc \
-	DownloadFailureException.h Logger.cc Logger.h LogFormatter.h \
-	SimpleLogFormatter.cc SimpleLogFormatter.h DiskWriter.h \
-	DiskWriterFactory.h AbstractDiskWriter.cc AbstractDiskWriter.h \
-	DefaultDiskWriter.cc DefaultDiskWriter.h \
+	DownloadFailureException.h Logger.cc Logger.h fmt.cc fmt.h \
+	DiskWriter.h DiskWriterFactory.h AbstractDiskWriter.cc \
+	AbstractDiskWriter.h DefaultDiskWriter.cc DefaultDiskWriter.h \
 	DefaultDiskWriterFactory.cc DefaultDiskWriterFactory.h File.cc \
 	File.h Option.cc Option.h Base64.cc Base64.h base32.cc \
 	base32.h LogFactory.cc LogFactory.h TimerA2.cc TimerA2.h \
@@ -882,13 +881,13 @@ am__objects_32 = SocketCore.$(OBJEXT) Command.$(OBJEXT) \
 	Request.$(OBJEXT) Exception.$(OBJEXT) FatalException.$(OBJEXT) \
 	RecoverableException.$(OBJEXT) DlAbortEx.$(OBJEXT) \
 	DlRetryEx.$(OBJEXT) DownloadFailureException.$(OBJEXT) \
-	Logger.$(OBJEXT) SimpleLogFormatter.$(OBJEXT) \
-	AbstractDiskWriter.$(OBJEXT) DefaultDiskWriter.$(OBJEXT) \
-	DefaultDiskWriterFactory.$(OBJEXT) File.$(OBJEXT) \
-	Option.$(OBJEXT) Base64.$(OBJEXT) base32.$(OBJEXT) \
-	LogFactory.$(OBJEXT) TimerA2.$(OBJEXT) TimeA2.$(OBJEXT) \
-	FeatureConfig.$(OBJEXT) DownloadEngineFactory.$(OBJEXT) \
-	SpeedCalc.$(OBJEXT) PeerStat.$(OBJEXT) BitfieldMan.$(OBJEXT) \
+	Logger.$(OBJEXT) fmt.$(OBJEXT) AbstractDiskWriter.$(OBJEXT) \
+	DefaultDiskWriter.$(OBJEXT) DefaultDiskWriterFactory.$(OBJEXT) \
+	File.$(OBJEXT) Option.$(OBJEXT) Base64.$(OBJEXT) \
+	base32.$(OBJEXT) LogFactory.$(OBJEXT) TimerA2.$(OBJEXT) \
+	TimeA2.$(OBJEXT) FeatureConfig.$(OBJEXT) \
+	DownloadEngineFactory.$(OBJEXT) SpeedCalc.$(OBJEXT) \
+	PeerStat.$(OBJEXT) BitfieldMan.$(OBJEXT) \
 	SimpleRandomizer.$(OBJEXT) HttpResponse.$(OBJEXT) \
 	HttpRequest.$(OBJEXT) Range.$(OBJEXT) \
 	AbstractProxyRequestCommand.$(OBJEXT) \
@@ -1199,10 +1198,9 @@ SRCS = Socket.h SocketCore.cc SocketCore.h BinaryStream.h Command.cc \
 	FatalException.h RecoverableException.cc \
 	RecoverableException.h DlAbortEx.cc DlAbortEx.h DlRetryEx.cc \
 	DlRetryEx.h DownloadFailureException.cc \
-	DownloadFailureException.h Logger.cc Logger.h LogFormatter.h \
-	SimpleLogFormatter.cc SimpleLogFormatter.h DiskWriter.h \
-	DiskWriterFactory.h AbstractDiskWriter.cc AbstractDiskWriter.h \
-	DefaultDiskWriter.cc DefaultDiskWriter.h \
+	DownloadFailureException.h Logger.cc Logger.h fmt.cc fmt.h \
+	DiskWriter.h DiskWriterFactory.h AbstractDiskWriter.cc \
+	AbstractDiskWriter.h DefaultDiskWriter.cc DefaultDiskWriter.h \
 	DefaultDiskWriterFactory.cc DefaultDiskWriterFactory.h File.cc \
 	File.h Option.cc Option.h Base64.cc Base64.h base32.cc \
 	base32.h LogFactory.cc LogFactory.h TimerA2.cc TimerA2.h \
@@ -1719,7 +1717,6 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/ShareRatioSeedCriteria.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/Signature.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/SimpleBtMessage.Po@am__quote@
-@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/SimpleLogFormatter.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/SimpleRandomizer.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/SingleFileAllocationIterator.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/SinkStreamFilter.Po@am__quote@
@@ -1776,6 +1773,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/cookie_helper.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/daemon.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/download_helper.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/fmt.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/gai_strerror.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/getaddrinfo.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/gettimeofday.Po@am__quote@
diff --git a/src/Metalink2RequestGroup.cc b/src/Metalink2RequestGroup.cc
index 6687b2c8..1f610937 100644
--- a/src/Metalink2RequestGroup.cc
+++ b/src/Metalink2RequestGroup.cc
@@ -55,6 +55,7 @@
 #include "A2STR.h"
 #include "a2functional.h"
 #include "download_helper.h"
+#include "fmt.h"
 #ifdef ENABLE_BITTORRENT
 # include "BtDependency.h"
 # include "download_helper.h"
@@ -66,8 +67,7 @@
 
 namespace aria2 {
 
-Metalink2RequestGroup::Metalink2RequestGroup():
-  logger_(LogFactory::getInstance()) {}
+Metalink2RequestGroup::Metalink2RequestGroup() {}
 
 namespace {
 class AccumulateNonP2PUri {
@@ -148,7 +148,7 @@ Metalink2RequestGroup::createRequestGroup
  const SharedHandle<Option>& option)
 {
   if(entries.empty()) {
-    logger_->notice(EX_NO_RESULT_WITH_YOUR_PREFS);
+    A2_LOG_NOTICE(EX_NO_RESULT_WITH_YOUR_PREFS);
     return;
   }
   std::vector<int32_t> selectIndexes =
@@ -197,7 +197,7 @@ Metalink2RequestGroup::createRequestGroup
         entryGroups.begin(), eoi = entryGroups.end(); itr != eoi; ++itr) {
     const std::string& metaurl = (*itr).first;
     const std::vector<SharedHandle<MetalinkEntry> >& mes = (*itr).second;
-    logger_->info("Processing metaurl group metaurl=%s", metaurl.c_str());
+    A2_LOG_INFO(fmt("Processing metaurl group metaurl=%s", metaurl.c_str()));
 #ifdef ENABLE_BITTORRENT
     SharedHandle<RequestGroup> torrentRg;
     if(!metaurl.empty()) {
@@ -233,7 +233,7 @@ Metalink2RequestGroup::createRequestGroup
     SharedHandle<DownloadContext> dctx;
     if(mes.size() == 1) {
       SharedHandle<MetalinkEntry> entry = mes[0];
-      logger_->info(MSG_METALINK_QUEUEING, entry->getPath().c_str());
+      A2_LOG_INFO(fmt(MSG_METALINK_QUEUEING, entry->getPath().c_str()));
       entry->reorderResourcesByPriority();
       std::vector<std::string> uris;
       std::for_each(entry->resources.begin(), entry->resources.end(),
@@ -286,9 +286,9 @@ Metalink2RequestGroup::createRequestGroup
       off_t offset = 0;
       for(std::vector<SharedHandle<MetalinkEntry> >::const_iterator i =
             mes.begin(), eoi = mes.end(); i != eoi; ++i) {
-        logger_->info("Metalink: Queueing %s for download as a member.",
-                      (*i)->getPath().c_str());
-        logger_->debug("originalName = %s", (*i)->metaurls[0]->name.c_str());
+        A2_LOG_INFO(fmt("Metalink: Queueing %s for download as a member.",
+                        (*i)->getPath().c_str()));
+        A2_LOG_DEBUG(fmt("originalName = %s", (*i)->metaurls[0]->name.c_str()));
         (*i)->reorderResourcesByPriority();
         std::vector<std::string> uris;
         std::for_each((*i)->resources.begin(), (*i)->resources.end(),
diff --git a/src/Metalink2RequestGroup.h b/src/Metalink2RequestGroup.h
index e75ccc84..d303cd5f 100644
--- a/src/Metalink2RequestGroup.h
+++ b/src/Metalink2RequestGroup.h
@@ -43,15 +43,12 @@
 namespace aria2 {
 
 class Option;
-class Logger;
 class RequestGroup;
 class BinaryStream;
 class MetalinkEntry;
 
 class Metalink2RequestGroup {
 private:
-  Logger* logger_;
-
   void
   createRequestGroup(std::vector<SharedHandle<RequestGroup> >& groups,
                      const std::vector<SharedHandle<MetalinkEntry> >& entries,
diff --git a/src/MetalinkPostDownloadHandler.cc b/src/MetalinkPostDownloadHandler.cc
index 3b142bfe..c6c86ad7 100644
--- a/src/MetalinkPostDownloadHandler.cc
+++ b/src/MetalinkPostDownloadHandler.cc
@@ -36,6 +36,7 @@
 #include "RequestGroup.h"
 #include "Metalink2RequestGroup.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "DiskAdaptor.h"
 #include "PieceStorage.h"
 #include "DownloadHandlerConstants.h"
@@ -45,6 +46,7 @@
 #include "Option.h"
 #include "DownloadContext.h"
 #include "download_helper.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -65,10 +67,8 @@ void MetalinkPostDownloadHandler::getNextRequestGroups
 (std::vector<SharedHandle<RequestGroup> >& groups,
  RequestGroup* requestGroup)
 {
-  if(getLogger()->debug()) {
-    getLogger()->debug("Generating RequestGroups for Metalink file %s",
-                       requestGroup->getFirstFilePath().c_str());
-  }
+  A2_LOG_DEBUG(fmt("Generating RequestGroups for Metalink file %s",
+                   requestGroup->getFirstFilePath().c_str()));
   SharedHandle<DiskAdaptor> diskAdaptor =
     requestGroup->getPieceStorage()->getDiskAdaptor();
   try {
diff --git a/src/MultiDiskAdaptor.cc b/src/MultiDiskAdaptor.cc
index 3e574613..aea21c43 100644
--- a/src/MultiDiskAdaptor.cc
+++ b/src/MultiDiskAdaptor.cc
@@ -47,14 +47,19 @@
 #include "DlAbortEx.h"
 #include "File.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "SimpleRandomizer.h"
 
 namespace aria2 {
 
-DiskWriterEntry::DiskWriterEntry(const SharedHandle<FileEntry>& fileEntry):
-  fileEntry_(fileEntry), open_(false), directIO_(false),
-  needsFileAllocation_(false) {}
+DiskWriterEntry::DiskWriterEntry(const SharedHandle<FileEntry>& fileEntry)
+  : fileEntry_(fileEntry),
+    open_(false),
+    directIO_(false),
+    needsFileAllocation_(false)
+{}
 
 const std::string& DiskWriterEntry::getFilePath() const
 {
@@ -138,11 +143,12 @@ void DiskWriterEntry::disableDirectIO()
   directIO_ = false;
 }
 
-MultiDiskAdaptor::MultiDiskAdaptor():
-  pieceLength_(0),
-  maxOpenFiles_(DEFAULT_MAX_OPEN_FILES),
-  directIOAllowed_(false),
-  readOnly_(false) {}
+MultiDiskAdaptor::MultiDiskAdaptor()
+  : pieceLength_(0),
+    maxOpenFiles_(DEFAULT_MAX_OPEN_FILES),
+    directIOAllowed_(false),
+    readOnly_(false)
+{}
 
 MultiDiskAdaptor::~MultiDiskAdaptor() {}
 
@@ -207,31 +213,25 @@ void MultiDiskAdaptor::resetDiskWriterEntries()
         off_t lastPieceStartOffset =
           (fileEntry->getOffset()+fileEntry->getLength()-1)/
           pieceLength_*pieceLength_;
-        if(getLogger()->debug()) {
-          getLogger()->debug("Checking adjacent backward file to %s"
-                             " whose lastPieceStartOffset+pieceLength_=%lld",
-                             fileEntry->getPath().c_str(),
-                             static_cast<long long int>
-                             (lastPieceStartOffset+pieceLength_));
-        }
+        A2_LOG_DEBUG(fmt("Checking adjacent backward file to %s"
+                         " whose lastPieceStartOffset+pieceLength_=%lld",
+                         fileEntry->getPath().c_str(),
+                         static_cast<long long int>
+                         (lastPieceStartOffset+pieceLength_)));
         ++itr;
         // adjacent backward files are not needed to be allocated. They
         // just requre DiskWriter
         for(; itr != eoi &&
               (!(*itr)->getFileEntry()->isRequested() ||
                (*itr)->getFileEntry()->getLength() == 0); ++itr) {
-          if(getLogger()->debug()) {
-            getLogger()->debug("file=%s, offset=%lld",
-                               (*itr)->getFileEntry()->getPath().c_str(),
-                               static_cast<long long int>
-                               ((*itr)->getFileEntry()->getOffset()));
-          }
+          A2_LOG_DEBUG(fmt("file=%s, offset=%lld",
+                           (*itr)->getFileEntry()->getPath().c_str(),
+                           static_cast<long long int>
+                           ((*itr)->getFileEntry()->getOffset())));
           if((*itr)->getFileEntry()->getOffset() <
              static_cast<off_t>(lastPieceStartOffset+pieceLength_)) {
-            if(getLogger()->debug()) {
-              getLogger()->debug("%s needs diskwriter",
-                                 (*itr)->getFileEntry()->getPath().c_str());
-            }
+            A2_LOG_DEBUG(fmt("%s needs diskwriter",
+                             (*itr)->getFileEntry()->getPath().c_str()));
             dwreq[(*itr)->getFileEntry()->getPath()] = true;
           } else {
             break;
@@ -251,10 +251,8 @@ void MultiDiskAdaptor::resetDiskWriterEntries()
     if((*i)->needsFileAllocation() ||
        dwreq.find((*i)->getFileEntry()->getPath()) != dwreq.end() ||
        (*i)->fileExists()) {
-      if(getLogger()->debug()) {
-        getLogger()->debug("Creating DiskWriter for filename=%s",
-                           (*i)->getFilePath().c_str());
-      }
+      A2_LOG_DEBUG(fmt("Creating DiskWriter for filename=%s",
+                       (*i)->getFilePath().c_str()));
       (*i)->setDiskWriter(dwFactory.newDiskWriter((*i)->getFilePath()));
       if(directIOAllowed_) {
         (*i)->getDiskWriter()->allowDirectIO();
@@ -279,8 +277,8 @@ void MultiDiskAdaptor::openIfNot
 (const SharedHandle<DiskWriterEntry>& entry, void (DiskWriterEntry::*open)())
 {
   if(!entry->isOpen()) {
-    //     getLogger()->debug("DiskWriterEntry: Cache MISS. offset=%s",
-    //            util::itos(entry->getFileEntry()->getOffset()).c_str());
+    //     A2_LOG_DEBUG(fmt("DiskWriterEntry: Cache MISS. offset=%s",
+    //            util::itos(entry->getFileEntry()->getOffset()).c_str()));
  
     size_t numOpened = openedDiskWriterEntries_.size();
     (entry.get()->*open)();
@@ -298,8 +296,8 @@ void MultiDiskAdaptor::openIfNot
       openedDiskWriterEntries_.push_back(entry);
     } 
   } else {
-    //     getLogger()->debug("DiskWriterEntry: Cache HIT. offset=%s",
-    //            util::itos(entry->getFileEntry()->getOffset()).c_str());
+    //     A2_LOG_DEBUG(fmt("DiskWriterEntry: Cache HIT. offset=%s",
+    //            util::itos(entry->getFileEntry()->getOffset()).c_str()));
   }
 }
 
diff --git a/src/MultiUrlRequestInfo.cc b/src/MultiUrlRequestInfo.cc
index edbfab88..e7e01fdb 100644
--- a/src/MultiUrlRequestInfo.cc
+++ b/src/MultiUrlRequestInfo.cc
@@ -56,6 +56,7 @@
 #include "AuthConfigFactory.h"
 #include "SessionSerializer.h"
 #include "TimeA2.h"
+#include "fmt.h"
 #ifdef ENABLE_SSL
 # include "SocketCore.h"
 # include "TLSContext.h"
@@ -94,12 +95,10 @@ MultiUrlRequestInfo::MultiUrlRequestInfo
  const SharedHandle<Option>& op,
  const SharedHandle<StatCalc>& statCalc,
  std::ostream& summaryOut)
-  :
-  requestGroups_(requestGroups),
-  option_(op),
-  statCalc_(statCalc),
-  summaryOut_(summaryOut),
-  logger_(LogFactory::getInstance())
+  : requestGroups_(requestGroups),
+    option_(op),
+    statCalc_(statCalc),
+    summaryOut_(summaryOut)
 {}
 
 MultiUrlRequestInfo::~MultiUrlRequestInfo() {}
@@ -124,10 +123,11 @@ downloadresultcode::RESULT MultiUrlRequestInfo::execute()
       File cookieFile(option_->get(PREF_LOAD_COOKIES));
       if(cookieFile.isFile()) {
         e->getCookieStorage()->load(cookieFile.getPath(), Time().getTime());
-        logger_->info("Loaded cookies from '%s'.",
-                      cookieFile.getPath().c_str());
+        A2_LOG_INFO(fmt("Loaded cookies from '%s'.",
+                        cookieFile.getPath().c_str()));
       } else {
-        logger_->error(MSG_LOADING_COOKIE_FAILED, cookieFile.getPath().c_str());
+        A2_LOG_ERROR(fmt(MSG_LOADING_COOKIE_FAILED,
+                         cookieFile.getPath().c_str()));
       }
     }
 
@@ -136,8 +136,8 @@ downloadresultcode::RESULT MultiUrlRequestInfo::execute()
     if(!option_->getAsBool(PREF_NO_NETRC) && netrccf.isFile()) {
       mode_t mode = netrccf.mode();
       if(mode&(S_IRWXG|S_IRWXO)) {
-        logger_->notice(MSG_INCORRECT_NETRC_PERMISSION,
-                        option_->get(PREF_NETRC_PATH).c_str());
+        A2_LOG_NOTICE(fmt(MSG_INCORRECT_NETRC_PERMISSION,
+                          option_->get(PREF_NETRC_PATH).c_str()));
       } else {
         SharedHandle<Netrc> netrc(new Netrc());
         netrc->parse(option_->get(PREF_NETRC_PATH));
@@ -155,10 +155,10 @@ downloadresultcode::RESULT MultiUrlRequestInfo::execute()
     }
     if(!option_->blank(PREF_CA_CERTIFICATE)) {
       if(!tlsContext->addTrustedCACertFile(option_->get(PREF_CA_CERTIFICATE))) {
-        logger_->info(MSG_WARN_NO_CA_CERT);
+        A2_LOG_INFO(MSG_WARN_NO_CA_CERT);
       }
     } else if(option_->getAsBool(PREF_CHECK_CERTIFICATE)) {
-      logger_->info(MSG_WARN_NO_CA_CERT);
+      A2_LOG_INFO(MSG_WARN_NO_CA_CERT);
     }
     if(option_->getAsBool(PREF_CHECK_CERTIFICATE)) {
       tlsContext->enablePeerVerification();
@@ -166,8 +166,8 @@ downloadresultcode::RESULT MultiUrlRequestInfo::execute()
     SocketCore::setTLSContext(tlsContext);
 #endif
     if(!Timer::monotonicClock()) {
-      logger_->warn("Don't change system time while aria2c is running."
-                    " Doing this may make aria2c hang for long time.");
+      A2_LOG_WARN("Don't change system time while aria2c is running."
+                  " Doing this may make aria2c hang for long time.");
     }
 
     std::string serverStatIf = option_->get(PREF_SERVER_STAT_IF);
@@ -212,18 +212,18 @@ downloadresultcode::RESULT MultiUrlRequestInfo::execute()
     if(!option_->blank(PREF_SAVE_SESSION)) {
       const std::string& filename = option_->get(PREF_SAVE_SESSION);
       if(sessionSerializer.save(filename)) {
-        logger_->notice("Serialized session to '%s' successfully.",
-                        filename.c_str());
+        A2_LOG_NOTICE(fmt("Serialized session to '%s' successfully.",
+                          filename.c_str()));
       } else {
-        logger_->notice("Failed to serialize session to '%s'.",
-                        filename.c_str());
+        A2_LOG_NOTICE(fmt("Failed to serialize session to '%s'.",
+                          filename.c_str()));
       }
     }
   } catch(RecoverableException& e) {
     if(returnValue == downloadresultcode::FINISHED) {
       returnValue = downloadresultcode::UNKNOWN_ERROR;
     }
-    logger_->error(EX_EXCEPTION_CAUGHT, e);
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
   }
 #ifdef SIGHUP
   util::setGlobalSignalHandler(SIGHUP, SIG_DFL, 0);
diff --git a/src/MultiUrlRequestInfo.h b/src/MultiUrlRequestInfo.h
index d3c4bb58..1ca4c4be 100644
--- a/src/MultiUrlRequestInfo.h
+++ b/src/MultiUrlRequestInfo.h
@@ -47,7 +47,6 @@ namespace aria2 {
 
 class RequestGroup;
 class Option;
-class Logger;
 class StatCalc;
 
 class MultiUrlRequestInfo {
@@ -60,10 +59,7 @@ private:
 
   std::ostream& summaryOut_;
 
-  Logger* logger_;
-
   void printMessageForContinue();
-
 public:
   MultiUrlRequestInfo
   (const std::vector<SharedHandle<RequestGroup> >& requestGroups,
diff --git a/src/PeerAbstractCommand.cc b/src/PeerAbstractCommand.cc
index d77afb66..6b068c1c 100644
--- a/src/PeerAbstractCommand.cc
+++ b/src/PeerAbstractCommand.cc
@@ -39,29 +39,32 @@
 #include "DlAbortEx.h"
 #include "Socket.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "message.h"
 #include "prefs.h"
 #include "DownloadFailureException.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "wallclock.h"
 #include "util.h"
 
 namespace aria2 {
 
-PeerAbstractCommand::PeerAbstractCommand(cuid_t cuid,
-                                         const SharedHandle<Peer>& peer,
-                                         DownloadEngine* e,
-                                         const SocketHandle& s):
-  Command(cuid),
-  checkPoint_(global::wallclock),
-  // TODO referring global option
-  timeout_(e->getOption()->getAsInt(PREF_BT_TIMEOUT)),
-  e_(e),
-  socket_(s),
-  peer_(peer),
-  checkSocketIsReadable_(false),
-  checkSocketIsWritable_(false),
-  noCheck_(false)
+PeerAbstractCommand::PeerAbstractCommand
+(cuid_t cuid,
+ const SharedHandle<Peer>& peer,
+ DownloadEngine* e,
+ const SocketHandle& s)
+ : Command(cuid),
+   checkPoint_(global::wallclock),
+   // TODO referring global option
+   timeout_(e->getOption()->getAsInt(PREF_BT_TIMEOUT)),
+   e_(e),
+   socket_(s),
+   peer_(peer),
+   checkSocketIsReadable_(false),
+   checkSocketIsWritable_(false),
+   noCheck_(false)
 {
   if(socket_ && socket_->isOpen()) {
     setReadCheckSocket(socket_);
@@ -76,14 +79,12 @@ PeerAbstractCommand::~PeerAbstractCommand()
 
 bool PeerAbstractCommand::execute()
 {
-  if(getLogger()->debug()) {
-    getLogger()->debug("CUID#%s -"
-                       " socket: read:%d, write:%d, hup:%d, err:%d, noCheck:%d",
-                       util::itos(getCuid()).c_str(),
-                       readEventEnabled(), writeEventEnabled(),
-                       hupEventEnabled(), errorEventEnabled(),
-                       noCheck_);
-  }
+  A2_LOG_DEBUG(fmt("CUID#%s -"
+                   " socket: read:%d, write:%d, hup:%d, err:%d, noCheck:%d",
+                   util::itos(getCuid()).c_str(),
+                   readEventEnabled(), writeEventEnabled(),
+                   hupEventEnabled(), errorEventEnabled(),
+                   noCheck_));
   if(exitBeforeExecute()) {
     onAbort();
     return true;
@@ -104,19 +105,18 @@ bool PeerAbstractCommand::execute()
     }
     return executeInternal();
   } catch(DownloadFailureException& err) {
-    getLogger()->error(EX_DOWNLOAD_ABORTED, err);
+    A2_LOG_ERROR_EX(EX_DOWNLOAD_ABORTED, err);
     onAbort();
     onFailure();
     return true;
   } catch(RecoverableException& err) {
-    if(getLogger()->debug()) {
-      getLogger()->debug(MSG_TORRENT_DOWNLOAD_ABORTED, err,
-                         util::itos(getCuid()).c_str());
-      getLogger()->debug(MSG_PEER_BANNED,
-                         util::itos(getCuid()).c_str(),
-                         peer_->getIPAddress().c_str(),
-                         peer_->getPort());
-    }
+    A2_LOG_DEBUG_EX(fmt(MSG_TORRENT_DOWNLOAD_ABORTED,
+                        util::itos(getCuid()).c_str()),
+                    err);
+    A2_LOG_DEBUG(fmt(MSG_PEER_BANNED,
+                     util::itos(getCuid()).c_str(),
+                     peer_->getIPAddress().c_str(),
+                     peer_->getPort()));
     onAbort();
     return prepareForNextPeer(0);
   }
diff --git a/src/PeerConnection.cc b/src/PeerConnection.cc
index 23d12093..cf31cd23 100644
--- a/src/PeerConnection.cc
+++ b/src/PeerConnection.cc
@@ -48,6 +48,7 @@
 #include "ARC4Encryptor.h"
 #include "ARC4Decryptor.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "util.h"
 #include "Peer.h"
 
@@ -55,18 +56,16 @@ namespace aria2 {
 
 PeerConnection::PeerConnection
 (cuid_t cuid, const SharedHandle<Peer>& peer, const SocketHandle& socket)
-
-  :cuid_(cuid),
-   peer_(peer),
-   socket_(socket),
-   logger_(LogFactory::getInstance()),
-   resbuf_(new unsigned char[MAX_PAYLOAD_LEN]),
-   resbufLength_(0),
-   currentPayloadLength_(0),
-   lenbufLength_(0),
-   socketBuffer_(socket),
-   encryptionEnabled_(false),
-   prevPeek_(false)
+  : cuid_(cuid),
+    peer_(peer),
+    socket_(socket),
+    resbuf_(new unsigned char[MAX_PAYLOAD_LEN]),
+    resbufLength_(0),
+    currentPayloadLength_(0),
+    lenbufLength_(0),
+    socketBuffer_(socket),
+    encryptionEnabled_(false),
+    prevPeek_(false)
 {}
 
 PeerConnection::~PeerConnection()
@@ -124,12 +123,10 @@ bool PeerConnection::receiveMessage(unsigned char* data, size_t& dataLength) {
         return false;
       }
       // we got EOF
-      if(logger_->debug()) {
-        logger_->debug("CUID#%s - In PeerConnection::receiveMessage(),"
+      A2_LOG_DEBUG(fmt("CUID#%s - In PeerConnection::receiveMessage(),"
                        " remain=%lu",
                        util::itos(cuid_).c_str(),
-                       static_cast<unsigned long>(temp));
-      }
+                       static_cast<unsigned long>(temp)));
       peer_->setDisconnectedGracefully(true);
       throw DL_ABORT_EX(EX_EOF_FROM_PEER);
     }
@@ -159,13 +156,11 @@ bool PeerConnection::receiveMessage(unsigned char* data, size_t& dataLength) {
         return false;
       }
       // we got EOF
-      if(logger_->debug()) {
-        logger_->debug("CUID#%s - In PeerConnection::receiveMessage(),"
+      A2_LOG_DEBUG(fmt("CUID#%s - In PeerConnection::receiveMessage(),"
                        " payloadlen=%lu, remaining=%lu",
                        util::itos(cuid_).c_str(),
                        static_cast<unsigned long>(currentPayloadLength_),
-                       static_cast<unsigned long>(temp));
-      }
+                       static_cast<unsigned long>(temp)));
       peer_->setDisconnectedGracefully(true);
       throw DL_ABORT_EX(EX_EOF_FROM_PEER);
     }
@@ -212,11 +207,10 @@ bool PeerConnection::receiveHandshake(unsigned char* data, size_t& dataLength,
           return false;
         }
         // we got EOF
-        if(logger_->debug()) {
-          logger_->debug
-            ("CUID#%s - In PeerConnection::receiveHandshake(), remain=%lu",
-             util::itos(cuid_).c_str(), static_cast<unsigned long>(temp));
-        }
+        A2_LOG_DEBUG
+          (fmt("CUID#%s - In PeerConnection::receiveHandshake(), remain=%lu",
+               util::itos(cuid_).c_str(),
+               static_cast<unsigned long>(temp)));
         peer_->setDisconnectedGracefully(true);
         throw DL_ABORT_EX(EX_EOF_FROM_PEER);
       }
@@ -273,9 +267,7 @@ bool PeerConnection::sendBufferIsEmpty() const
 ssize_t PeerConnection::sendPendingData()
 {
   ssize_t writtenLength = socketBuffer_.send();
-  if(logger_->debug()) {
-    logger_->debug("sent %ld byte(s).", static_cast<long int>(writtenLength));
-  }
+  A2_LOG_DEBUG(fmt("sent %ld byte(s).", static_cast<long int>(writtenLength)));
   return writtenLength;
 }
 
diff --git a/src/PeerConnection.h b/src/PeerConnection.h
index fd2acd7a..0557204d 100644
--- a/src/PeerConnection.h
+++ b/src/PeerConnection.h
@@ -45,7 +45,6 @@
 
 namespace aria2 {
 
-class Logger;
 class Peer;
 class SocketCore;
 class ARC4Encryptor;
@@ -60,7 +59,6 @@ private:
   cuid_t cuid_;
   SharedHandle<Peer> peer_;
   SharedHandle<SocketCore> socket_;
-  Logger* logger_;
 
   unsigned char* resbuf_;
   size_t resbufLength_;
diff --git a/src/PeerInitiateConnectionCommand.cc b/src/PeerInitiateConnectionCommand.cc
index 95e62869..3c258d57 100644
--- a/src/PeerInitiateConnectionCommand.cc
+++ b/src/PeerInitiateConnectionCommand.cc
@@ -41,6 +41,7 @@
 #include "prefs.h"
 #include "Socket.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "Peer.h"
 #include "BtRuntime.h"
 #include "PeerStorage.h"
@@ -48,6 +49,7 @@
 #include "PeerConnection.h"
 #include "RequestGroup.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -58,11 +60,10 @@ PeerInitiateConnectionCommand::PeerInitiateConnectionCommand
  DownloadEngine* e,
  const SharedHandle<BtRuntime>& btRuntime,
  bool mseHandshakeEnabled)
-  :
-  PeerAbstractCommand(cuid, peer, e),
-  requestGroup_(requestGroup),
-  btRuntime_(btRuntime),
-  mseHandshakeEnabled_(mseHandshakeEnabled)
+  : PeerAbstractCommand(cuid, peer, e),
+    requestGroup_(requestGroup),
+    btRuntime_(btRuntime),
+    mseHandshakeEnabled_(mseHandshakeEnabled)
 {
   btRuntime_->increaseConnections();
   requestGroup_->increaseNumCommand();
@@ -75,12 +76,10 @@ PeerInitiateConnectionCommand::~PeerInitiateConnectionCommand()
 }
 
 bool PeerInitiateConnectionCommand::executeInternal() {
-  if(getLogger()->info()) {
-    getLogger()->info(MSG_CONNECTING_TO_SERVER,
-                      util::itos(getCuid()).c_str(),
-                      getPeer()->getIPAddress().c_str(),
-                      getPeer()->getPort());
-  }
+  A2_LOG_INFO(fmt(MSG_CONNECTING_TO_SERVER,
+                  util::itos(getCuid()).c_str(),
+                  getPeer()->getIPAddress().c_str(),
+                  getPeer()->getPort()));
   createSocket();
   getSocket()->establishConnection(getPeer()->getIPAddress(),
                                    getPeer()->getPort());
diff --git a/src/PeerListenCommand.cc b/src/PeerListenCommand.cc
index 25188e07..2ce07b38 100644
--- a/src/PeerListenCommand.cc
+++ b/src/PeerListenCommand.cc
@@ -44,9 +44,11 @@
 #include "message.h"
 #include "ReceiverMSEHandshakeCommand.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "Socket.h"
 #include "SimpleRandomizer.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -57,11 +59,13 @@ PeerListenCommand* PeerListenCommand::instance_ = 0;
 PeerListenCommand* PeerListenCommand::instance6_ = 0;
 
 PeerListenCommand::PeerListenCommand
-(cuid_t cuid, DownloadEngine* e, int family):
-  Command(cuid),
-  e_(e),
-  family_(family),
-  lowestSpeedLimit_(20*1024)
+(cuid_t cuid,
+ DownloadEngine* e,
+ int family)
+  : Command(cuid),
+    e_(e),
+    family_(family),
+    lowestSpeedLimit_(20*1024)
 {
   ++numInstance_;
 }
@@ -89,12 +93,13 @@ bool PeerListenCommand::bindPort(uint16_t& port, IntSequence& seq)
       socket_->bind(A2STR::NIL, port, family_);
       socket_->beginListen();
       socket_->setNonBlockingMode();
-      getLogger()->notice("IPv%d BitTorrent: listening to port %d",
-                          family_ == AF_INET?4:6, port);
+      A2_LOG_NOTICE(fmt("IPv%d BitTorrent: listening to port %d",
+                        family_ == AF_INET?4:6, port));
       return true;
     } catch(RecoverableException& ex) {
-      getLogger()->error(MSG_BIND_FAILURE, ex,
-                         util::itos(getCuid()).c_str(), port);
+      A2_LOG_ERROR_EX(fmt(MSG_BIND_FAILURE,
+                          util::itos(getCuid()).c_str(), port),
+                      ex);
       socket_->closeConnection();
     }
   }
@@ -130,16 +135,16 @@ bool PeerListenCommand::execute() {
       Command* command =
         new ReceiverMSEHandshakeCommand(cuid, peer, e_, peerSocket);
       e_->addCommand(command);
-      if(getLogger()->debug()) {
-        getLogger()->debug("Accepted the connection from %s:%u.",
-                           peer->getIPAddress().c_str(),
-                           peer->getPort());
-        getLogger()->debug("Added CUID#%s to receive BitTorrent/MSE handshake.",
-                           util::itos(cuid).c_str());
-      }
+      A2_LOG_DEBUG(fmt("Accepted the connection from %s:%u.",
+                       peer->getIPAddress().c_str(),
+                       peer->getPort()));
+      A2_LOG_DEBUG(fmt("Added CUID#%s to receive BitTorrent/MSE handshake.",
+                       util::itos(cuid).c_str()));
     } catch(RecoverableException& ex) {
-      getLogger()->debug(MSG_ACCEPT_FAILURE, ex, util::itos(getCuid()).c_str());
-    }               
+      A2_LOG_DEBUG_EX(fmt(MSG_ACCEPT_FAILURE,
+                          util::itos(getCuid()).c_str()),
+                      ex);
+    }
   }
   e_->addCommand(this);
   return false;
diff --git a/src/PeerReceiveHandshakeCommand.cc b/src/PeerReceiveHandshakeCommand.cc
index 867399ab..d2de0ac8 100644
--- a/src/PeerReceiveHandshakeCommand.cc
+++ b/src/PeerReceiveHandshakeCommand.cc
@@ -49,10 +49,12 @@
 #include "message.h"
 #include "Socket.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "prefs.h"
 #include "Option.h"
 #include "RequestGroupMan.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "RequestGroup.h"
 
 namespace aria2 {
@@ -63,9 +65,8 @@ PeerReceiveHandshakeCommand::PeerReceiveHandshakeCommand
  DownloadEngine* e,
  const SocketHandle& s,
  const SharedHandle<PeerConnection>& peerConnection)
-  :
-  PeerAbstractCommand(cuid, peer, e, s),
-  peerConnection_(peerConnection)
+  : PeerAbstractCommand(cuid, peer, e, s),
+    peerConnection_(peerConnection)
 {
   if(!peerConnection_) {
     peerConnection_.reset(new PeerConnection(cuid, getPeer(), getSocket()));
@@ -110,8 +111,8 @@ bool PeerReceiveHandshakeCommand::executeInternal()
                       util::toHex(infoHash).c_str()).str());
     }
     if(btRuntime->isHalt()) {
-      getLogger()->debug("Info hash found but the download is over."
-                         " Dropping connection.");
+      A2_LOG_DEBUG("Info hash found but the download is over."
+                   " Dropping connection.");
       return true;
     }
     TransferStat tstat =
@@ -143,11 +144,9 @@ bool PeerReceiveHandshakeCommand::executeInternal()
            PeerInteractionCommand::RECEIVER_WAIT_HANDSHAKE,
            peerConnection_);
         getDownloadEngine()->addCommand(command);
-        if(getLogger()->debug()) {
-          getLogger()->debug(MSG_INCOMING_PEER_CONNECTION,
-                             util::itos(getCuid()).c_str(),
-                             util::itos(getPeer()->usedBy()).c_str());
-        }
+        A2_LOG_DEBUG(fmt(MSG_INCOMING_PEER_CONNECTION,
+                         util::itos(getCuid()).c_str(),
+                         util::itos(getPeer()->usedBy()).c_str()));
       }
     }
     return true;
diff --git a/src/PollEventPoll.cc b/src/PollEventPoll.cc
index 1af0771d..e5933e24 100644
--- a/src/PollEventPoll.cc
+++ b/src/PollEventPoll.cc
@@ -42,11 +42,13 @@
 #include "LogFactory.h"
 #include "Logger.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-PollEventPoll::KSocketEntry::KSocketEntry(sock_t s):
-  SocketEntry<KCommandEvent, KADNSEvent>(s) {}
+PollEventPoll::KSocketEntry::KSocketEntry(sock_t s)
+  : SocketEntry<KCommandEvent, KADNSEvent>(s)
+{}
 
 int accumulateEvent(int events, const PollEventPoll::KEvent& event)
 {
@@ -73,8 +75,9 @@ struct pollfd PollEventPoll::KSocketEntry::getEvents()
   return pollEvent;
 }
 
-PollEventPoll::PollEventPoll():
-  pollfdCapacity_(1024), pollfdNum_(0), logger_(LogFactory::getInstance())
+PollEventPoll::PollEventPoll()
+  : pollfdCapacity_(1024),
+    pollfdNum_(0)
 {
   pollfds_ = new struct pollfd[pollfdCapacity_];
 }
@@ -103,10 +106,8 @@ void PollEventPoll::poll(const struct timeval& tv)
         if(itr != socketEntries_.end() && *(*itr) == *se) {
           (*itr)->processEvents(first->revents);
         } else {
-          if(logger_->debug()) {
-            logger_->debug("Socket %d is not found in SocketEntries.",
-                           first->fd);
-          }
+          A2_LOG_DEBUG(fmt("Socket %d is not found in SocketEntries.",
+                           first->fd));
         }
       }
     }
@@ -221,9 +222,7 @@ bool PollEventPoll::deleteEvents
     }
     return true;
   } else {
-    if(logger_->debug()) {
-      logger_->debug("Socket %d is not found in SocketEntries.", socket);
-    }
+    A2_LOG_DEBUG(fmt("Socket %d is not found in SocketEntries.", socket));
     return false;
   }
 }
diff --git a/src/PollEventPoll.h b/src/PollEventPoll.h
index eddac2c9..b07a5308 100644
--- a/src/PollEventPoll.h
+++ b/src/PollEventPoll.h
@@ -48,8 +48,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class PollEventPoll : public EventPoll {
 private:
   class KSocketEntry;
@@ -84,8 +82,6 @@ private:
 
   struct pollfd* pollfds_;
 
-  Logger* logger_;
-
   bool addEvents(sock_t socket, const KEvent& event);
 
   bool deleteEvents(sock_t socket, const KEvent& event);
diff --git a/src/PortEventPoll.cc b/src/PortEventPoll.cc
index 363c619f..10766a67 100644
--- a/src/PortEventPoll.cc
+++ b/src/PortEventPoll.cc
@@ -43,11 +43,13 @@
 #include "LogFactory.h"
 #include "Logger.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-PortEventPoll::KSocketEntry::KSocketEntry(sock_t s):
-  SocketEntry<KCommandEvent, KADNSEvent>(s) {}
+PortEventPoll::KSocketEntry::KSocketEntry(sock_t s)
+  : SocketEntry<KCommandEvent, KADNSEvent>(s)
+{}
 
 int accumulateEvent(int events, const PortEventPoll::KEvent& event)
 {
@@ -74,10 +76,9 @@ PortEventPoll::A2PortEvent PortEventPoll::KSocketEntry::getEvents()
   return portEvent;
 }
 
-PortEventPoll::PortEventPoll():
-  portEventsSize_(PORT_EVENTS_SIZE),
-  portEvents_(new port_event_t[portEventsSize_]),
-  logger_(LogFactory::getInstance())
+PortEventPoll::PortEventPoll()
+  : portEventsSize_(PORT_EVENTS_SIZE),
+    portEvents_(new port_event_t[portEventsSize_])
 {
   port_ = port_create();
 }
@@ -89,8 +90,9 @@ PortEventPoll::~PortEventPoll()
     while((r = close(port_)) == -1 && errno == EINTR);
     int errNum = errno;
     if(r == -1) {
-      logger_->error("Error occurred while closing port %d: %s",
-                     port_, util::safeStrerror(errNum).c_str());
+      A2_LOG_ERROR(fmt("Error occurred while closing port %d: %s",
+                       port_,
+                       util::safeStrerror(errNum).c_str()));
     }
   }
   delete [] portEvents_;
@@ -114,9 +116,7 @@ void PortEventPoll::poll(const struct timeval& tv)
   if(res == 0 ||
      (res == -1 && (errno == ETIME || errno == EINTR) &&
       portEvents_[0].portev_user != (void*)-1)) {
-    if(logger_->debug()) {
-      logger_->debug("nget=%u", nget);
-    }
+    A2_LOG_DEBUG(fmt("nget=%u", nget));
     for(uint_t i = 0; i < nget; ++i) {
       const port_event_t& pev = portEvents_[i];
       KSocketEntry* p = reinterpret_cast<KSocketEntry*>(pev.portev_user);
@@ -125,8 +125,10 @@ void PortEventPoll::poll(const struct timeval& tv)
                              p->getEvents().events, p);
       int errNum = errno;
       if(r == -1) {
-        logger_->error("port_associate failed for file descriptor %d: cause %s",
-                       pev.portev_object, util::safeStrerror(errNum).c_str());
+        A2_LOG_ERROR(fmt("port_associate failed for file descriptor %d:"
+                         " cause %s",
+                         pev.portev_object,
+                         util::safeStrerror(errNum).c_str()));
       }
     }
   }
@@ -197,10 +199,8 @@ bool PortEventPoll::addEvents(sock_t socket,
     errNum = r;
   }
   if(r == -1) {
-    if(logger_->debug()) {
-      logger_->debug("Failed to add socket event %d:%s",
-                     socket, util::safeStrerror(errNum).c_str());
-    }
+    A2_LOG_DEBUG(fmt("Failed to add socket event %d:%s",
+                     socket, util::safeStrerror(errNum).c_str()));
     return false;
   } else {
     return true;
@@ -244,18 +244,14 @@ bool PortEventPoll::deleteEvents(sock_t socket,
       errNum = errno;
     }
     if(r == -1) {
-      if(logger_->debug()) {
-        logger_->debug("Failed to delete socket event:%s",
-                       util::safeStrerror(errNum).c_str());
-      }
+      A2_LOG_DEBUG(fmt("Failed to delete socket event:%s",
+                       util::safeStrerror(errNum).c_str()));
       return false;
     } else {
       return true;
     }
   } else {
-    if(logger_->debug()) {
-      logger_->debug("Socket %d is not found in SocketEntries.", socket);
-    }
+    A2_LOG_DEBUG(fmt("Socket %d is not found in SocketEntries.", socket));
     return false;
   }
 }
diff --git a/src/PortEventPoll.h b/src/PortEventPoll.h
index 9abc7d81..937e629e 100644
--- a/src/PortEventPoll.h
+++ b/src/PortEventPoll.h
@@ -50,8 +50,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class PortEventPoll : public EventPoll {
 private:
   class KSocketEntry;
@@ -91,8 +89,6 @@ private:
 
   static const size_t PORT_EVENTS_SIZE = 1024;
 
-  Logger* logger_;
-
   bool addEvents(sock_t socket, const KEvent& event);
 
   bool deleteEvents(sock_t socket, const KEvent& event);
diff --git a/src/RequestGroup.cc b/src/RequestGroup.cc
index 22472325..88c2ea79 100644
--- a/src/RequestGroup.cc
+++ b/src/RequestGroup.cc
@@ -69,6 +69,7 @@
 #include "Request.h"
 #include "FileAllocationIterator.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "A2STR.h"
 #include "URISelector.h"
 #include "InOrderURISelector.h"
@@ -121,35 +122,34 @@ namespace aria2 {
 
 gid_t RequestGroup::gidCounter_ = 0;
 
-RequestGroup::RequestGroup(const SharedHandle<Option>& option):
-  gid_(newGID()),
-  option_(new Option(*option.get())),
-  numConcurrentCommand_(option->getAsInt(PREF_SPLIT)),
-  numStreamConnection_(0),
-  numStreamCommand_(0),
-  numCommand_(0),
-  saveControlFile_(true),
-  progressInfoFile_(new NullProgressInfoFile()),
-  preLocalFileCheckEnabled_(true),
-  haltRequested_(false),
-  forceHaltRequested_(false),
-  haltReason_(RequestGroup::NONE),
-  pauseRequested_(false),
-  uriSelector_(new InOrderURISelector()),
-  lastModifiedTime_(Time::null()),
-  fileNotFoundCount_(0),
-  timeout_(option->getAsInt(PREF_TIMEOUT)),
+RequestGroup::RequestGroup(const SharedHandle<Option>& option)
+  : gid_(newGID()),
+    option_(new Option(*option.get())),
+    numConcurrentCommand_(option->getAsInt(PREF_SPLIT)),
+    numStreamConnection_(0),
+    numStreamCommand_(0),
+    numCommand_(0),
+    saveControlFile_(true),
+    progressInfoFile_(new NullProgressInfoFile()),
+    preLocalFileCheckEnabled_(true),
+    haltRequested_(false),
+    forceHaltRequested_(false),
+    haltReason_(RequestGroup::NONE),
+    pauseRequested_(false),
+    uriSelector_(new InOrderURISelector()),
+    lastModifiedTime_(Time::null()),
+    fileNotFoundCount_(0),
+    timeout_(option->getAsInt(PREF_TIMEOUT)),
 #ifdef ENABLE_BITTORRENT
-  btRuntime_(0),
-  peerStorage_(0),
+    btRuntime_(0),
+    peerStorage_(0),
 #endif // ENABLE_BITTORRENT
-  inMemoryDownload_(false),
-  maxDownloadSpeedLimit_(option->getAsInt(PREF_MAX_DOWNLOAD_LIMIT)),
-  maxUploadSpeedLimit_(option->getAsInt(PREF_MAX_UPLOAD_LIMIT)),
-  belongsToGID_(0),
-  requestGroupMan_(0),
-  resumeFailureCount_(0),
-  logger_(LogFactory::getInstance())
+    inMemoryDownload_(false),
+    maxDownloadSpeedLimit_(option->getAsInt(PREF_MAX_DOWNLOAD_LIMIT)),
+    maxUploadSpeedLimit_(option->getAsInt(PREF_MAX_UPLOAD_LIMIT)),
+    belongsToGID_(0),
+    requestGroupMan_(0),
+    resumeFailureCount_(0)
 {
   fileAllocationEnabled_ = option_->get(PREF_FILE_ALLOCATION) != V_NONE;
   // Add types to be sent as a Accept header value here.
@@ -235,9 +235,7 @@ SharedHandle<CheckIntegrityEntry> RequestGroup::createCheckIntegrityEntry()
     if(downloadFinished()) {
 #ifdef ENABLE_MESSAGE_DIGEST
       if(downloadContext_->isChecksumVerificationNeeded()) {
-        if(logger_->info()) {
-          logger_->info(MSG_HASH_CHECK_NOT_DONE);
-        }
+        A2_LOG_INFO(MSG_HASH_CHECK_NOT_DONE);
         ChecksumCheckIntegrityEntry* tempEntry =
           new ChecksumCheckIntegrityEntry(this);
         tempEntry->setRedownload(true);
@@ -246,9 +244,9 @@ SharedHandle<CheckIntegrityEntry> RequestGroup::createCheckIntegrityEntry()
 #endif // ENABLE_MESSAGE_DIGEST
         {
           downloadContext_->setChecksumVerified(true);
-          logger_->notice(MSG_DOWNLOAD_ALREADY_COMPLETED,
-                          util::itos(gid_).c_str(),
-                          downloadContext_->getBasePath().c_str());
+          A2_LOG_NOTICE(fmt(MSG_DOWNLOAD_ALREADY_COMPLETED,
+                            util::itos(gid_).c_str(),
+                            downloadContext_->getBasePath().c_str()));
         }
     } else {
       checkEntry.reset(new StreamCheckIntegrityEntry(this));
@@ -267,9 +265,9 @@ SharedHandle<CheckIntegrityEntry> RequestGroup::createCheckIntegrityEntry()
 #endif // ENABLE_MESSAGE_DIGEST
       {
         downloadContext_->setChecksumVerified(true);
-        logger_->notice(MSG_DOWNLOAD_ALREADY_COMPLETED,
-                        util::itos(gid_).c_str(),
-                        downloadContext_->getBasePath().c_str());
+        A2_LOG_NOTICE(fmt(MSG_DOWNLOAD_ALREADY_COMPLETED,
+                          util::itos(gid_).c_str(),
+                          downloadContext_->getBasePath().c_str()));
       }
   } else {
     loadAndOpenFile(infoFile);
@@ -378,8 +376,8 @@ void RequestGroup::createInitialCommand
             e->addCommand(dhtCommands);
           }
         } else {
-          logger_->notice("For BitTorrent Magnet URI, enabling DHT is strongly"
-                          " recommended. See --enable-dht option.");
+          A2_LOG_NOTICE("For BitTorrent Magnet URI, enabling DHT is strongly"
+                        " recommended. See --enable-dht option.");
         }
 
         SharedHandle<CheckIntegrityEntry> entry
@@ -398,12 +396,11 @@ void RequestGroup::createInitialCommand
         } else {
           // Open file in writable mode to allow the program
           // truncate the file to downloadContext_->getTotalLength()
-          if(logger_->debug()) {
-            logger_->debug("File size not match. File is opened in writable"
-                           " mode. Expected:%s Actual:%s",
-                           util::uitos(downloadContext_->getTotalLength()).c_str(),
-                           util::uitos(actualFileSize).c_str());
-          }
+          A2_LOG_DEBUG
+            (fmt("File size not match. File is opened in writable"
+                 " mode. Expected:%s Actual:%s",
+                 util::uitos(downloadContext_->getTotalLength()).c_str(),
+                 util::uitos(actualFileSize).c_str()));
         }
       }
       // Call Load, Save and file allocation command here
@@ -600,9 +597,7 @@ void RequestGroup::initPieceStorage()
         // Use LongestSequencePieceSelector when HTTP/FTP/BitTorrent
         // integrated downloads. Currently multi-file integrated
         // download is not supported.
-        if(logger_->debug()) {
-          logger_->debug("Using LongestSequencePieceSelector");
-        }
+        A2_LOG_DEBUG("Using LongestSequencePieceSelector");
         SharedHandle<PieceSelector> longestPieceSelector
           (new LongestSequencePieceSelector());
         ps->setPieceSelector(longestPieceSelector);
@@ -684,8 +679,9 @@ void RequestGroup::adjustFilename
      option_->getAsBool(PREF_REMOVE_CONTROL_FILE) &&
      infoFile->exists()) {
     infoFile->removeFile();
-    logger_->notice("Removed control file for %s because it is requested by"
-                    " user.", infoFile->getFilename().c_str());
+    A2_LOG_NOTICE(fmt("Removed control file for %s because it is requested by"
+                      " user.",
+                      infoFile->getFilename().c_str()));
   }
   if(infoFile->exists()) {
     // Use current filename
@@ -717,9 +713,9 @@ void RequestGroup::removeDefunctControlFile
   if(progressInfoFile->exists() &&
      !pieceStorage_->getDiskAdaptor()->fileExists()) {
     progressInfoFile->removeFile();
-    logger_->notice(MSG_REMOVED_DEFUNCT_CONTROL_FILE,
-                    progressInfoFile->getFilename().c_str(),
-                    downloadContext_->getBasePath().c_str());
+    A2_LOG_NOTICE(fmt(MSG_REMOVED_DEFUNCT_CONTROL_FILE,
+                      progressInfoFile->getFilename().c_str(),
+                      downloadContext_->getBasePath().c_str()));
   }
 }
 
@@ -769,7 +765,7 @@ void RequestGroup::shouldCancelDownloadForSafety()
   if(outfile.exists()) {
     if(option_->getAsBool(PREF_AUTO_FILE_RENAMING)) {
       if(tryAutoFileRenaming()) {
-        logger_->notice(MSG_FILE_RENAMED, getFirstFilePath().c_str());
+        A2_LOG_NOTICE(fmt(MSG_FILE_RENAMED, getFirstFilePath().c_str()));
       } else {
         throw DOWNLOAD_FAILURE_EXCEPTION
           (StringFormat("File renaming failed: %s",
@@ -966,9 +962,7 @@ void RequestGroup::decreaseNumCommand()
 {
   --numCommand_;
   if(!numCommand_ && requestGroupMan_) {
-    if(logger_->debug()) {
-      logger_->debug("GID#%s - Request queue check", util::itos(gid_).c_str());
-    }
+    A2_LOG_DEBUG(fmt("GID#%s - Request queue check", util::itos(gid_).c_str()));
     requestGroupMan_->requestQueueCheck();
   }
 }
@@ -1033,10 +1027,8 @@ void RequestGroup::releaseRuntimeResource(DownloadEngine* e)
 
 void RequestGroup::preDownloadProcessing()
 {
-  if(logger_->debug()) {
-    logger_->debug("Finding PreDownloadHandler for path %s.",
-                   getFirstFilePath().c_str());
-  }
+  A2_LOG_DEBUG(fmt("Finding PreDownloadHandler for path %s.",
+                   getFirstFilePath().c_str()));
   try {
     for(std::vector<SharedHandle<PreDownloadHandler> >::const_iterator itr =
           preDownloadHandlers_.begin(), eoi = preDownloadHandlers_.end();
@@ -1047,22 +1039,18 @@ void RequestGroup::preDownloadProcessing()
       }
     }
   } catch(RecoverableException& ex) {
-    logger_->error(EX_EXCEPTION_CAUGHT, ex);
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, ex);
     return;
   }
-  if(logger_->debug()) {
-    logger_->debug("No PreDownloadHandler found.");
-  }
+  A2_LOG_DEBUG("No PreDownloadHandler found.");
   return;
 }
 
 void RequestGroup::postDownloadProcessing
 (std::vector<SharedHandle<RequestGroup> >& groups)
 {
-  if(logger_->debug()) {
-    logger_->debug("Finding PostDownloadHandler for path %s.",
-                   getFirstFilePath().c_str());
-  }
+  A2_LOG_DEBUG(fmt("Finding PostDownloadHandler for path %s.",
+                   getFirstFilePath().c_str()));
   try {
     for(std::vector<SharedHandle<PostDownloadHandler> >::const_iterator itr =
           postDownloadHandlers_.begin(), eoi = postDownloadHandlers_.end();
@@ -1073,11 +1061,9 @@ void RequestGroup::postDownloadProcessing
       }
     }
   } catch(RecoverableException& ex) {
-    logger_->error(EX_EXCEPTION_CAUGHT, ex);
-  }
-  if(logger_->debug()) {
-    logger_->debug("No PostDownloadHandler found.");
+    A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, ex);
   }
+  A2_LOG_DEBUG("No PostDownloadHandler found.");
 }
 
 void RequestGroup::initializePreDownloadHandler()
@@ -1169,10 +1155,8 @@ bool RequestGroup::needsFileAllocation() const
 
 DownloadResultHandle RequestGroup::createDownloadResult() const
 {
-  if(logger_->debug()) {
-    logger_->debug("GID#%s - Creating DownloadResult.",
-                   util::itos(gid_).c_str());
-  }
+  A2_LOG_DEBUG(fmt("GID#%s - Creating DownloadResult.",
+                   util::itos(gid_).c_str()));
   TransferStat st = calculateStat();
   SharedHandle<DownloadResult> res(new DownloadResult());
   res->gid = gid_;
@@ -1207,8 +1191,8 @@ DownloadResultHandle RequestGroup::createDownloadResult() const
   
 void RequestGroup::reportDownloadFinished()
 {
-  logger_->notice(MSG_FILE_DOWNLOAD_COMPLETED,
-                  downloadContext_->getBasePath().c_str());
+  A2_LOG_NOTICE(fmt(MSG_FILE_DOWNLOAD_COMPLETED,
+                    downloadContext_->getBasePath().c_str()));
   uriSelector_->resetCounters();
 #ifdef ENABLE_BITTORRENT
   if(downloadContext_->hasAttribute(bittorrent::BITTORRENT)) {
@@ -1218,10 +1202,10 @@ void RequestGroup::reportDownloadFinished()
     SharedHandle<TorrentAttribute> attrs =
       bittorrent::getTorrentAttrs(downloadContext_);
     if(!attrs->metadata.empty()) {
-      logger_->notice(MSG_SHARE_RATIO_REPORT,
-                      shareRatio,
-                      util::abbrevSize(stat.getAllTimeUploadLength()).c_str(),
-                      util::abbrevSize(getCompletedLength()).c_str());
+      A2_LOG_NOTICE(fmt(MSG_SHARE_RATIO_REPORT,
+                        shareRatio,
+                        util::abbrevSize(stat.getAllTimeUploadLength()).c_str(),
+                        util::abbrevSize(getCompletedLength()).c_str()));
     }
   }
 #endif // ENABLE_BITTORRENT
@@ -1248,12 +1232,12 @@ void RequestGroup::setURISelector(const SharedHandle<URISelector>& uriSelector)
 void RequestGroup::applyLastModifiedTimeToLocalFiles()
 {
   if(pieceStorage_ && lastModifiedTime_.good()) {
-    logger_->info("Applying Last-Modified time: %s",
-                  lastModifiedTime_.toHTTPDate().c_str());
+    A2_LOG_INFO(fmt("Applying Last-Modified time: %s",
+                    lastModifiedTime_.toHTTPDate().c_str()));
     size_t n =
       pieceStorage_->getDiskAdaptor()->utime(Time(), lastModifiedTime_);
-    logger_->info("Last-Modified attrs of %lu files were updated.",
-                  static_cast<unsigned long>(n));
+    A2_LOG_INFO(fmt("Last-Modified attrs of %lu files were updated.",
+                    static_cast<unsigned long>(n)));
   }
 }
 
diff --git a/src/RequestGroup.h b/src/RequestGroup.h
index 378a4876..8bc8dc22 100644
--- a/src/RequestGroup.h
+++ b/src/RequestGroup.h
@@ -62,7 +62,6 @@ class PreDownloadHandler;
 class PostDownloadHandler;
 class DiskWriterFactory;
 class Option;
-class Logger;
 class RequestGroup;
 class CheckIntegrityEntry;
 struct DownloadResult;
@@ -176,8 +175,6 @@ private:
 
   int resumeFailureCount_;
 
-  Logger* logger_;
-
   void validateFilename(const std::string& expectedFilename,
                         const std::string& actualFilename) const;
 
diff --git a/src/RequestGroupMan.cc b/src/RequestGroupMan.cc
index a9181afa..1b4cc68e 100644
--- a/src/RequestGroupMan.cc
+++ b/src/RequestGroupMan.cc
@@ -67,6 +67,7 @@
 #include "Command.h"
 #include "FileEntry.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "FileAllocationEntry.h"
 #include "CheckIntegrityEntry.h"
 #include "Segment.h"
@@ -80,20 +81,20 @@ namespace aria2 {
 RequestGroupMan::RequestGroupMan
 (const std::vector<SharedHandle<RequestGroup> >& requestGroups,
  unsigned int maxSimultaneousDownloads,
- const Option* option):
-  reservedGroups_(requestGroups.begin(), requestGroups.end()),
-  logger_(LogFactory::getInstance()),
-  maxSimultaneousDownloads_(maxSimultaneousDownloads),
-  option_(option),
-  serverStatMan_(new ServerStatMan()),
-  maxOverallDownloadSpeedLimit_
-  (option->getAsInt(PREF_MAX_OVERALL_DOWNLOAD_LIMIT)),
-  maxOverallUploadSpeedLimit_(option->getAsInt(PREF_MAX_OVERALL_UPLOAD_LIMIT)),
-  xmlRpc_(option->getAsBool(PREF_ENABLE_XML_RPC)),
-  queueCheck_(true),
-  removedErrorResult_(0),
-  removedLastErrorResult_(downloadresultcode::FINISHED),
-  maxDownloadResult_(option->getAsInt(PREF_MAX_DOWNLOAD_RESULT))
+ const Option* option)
+  : reservedGroups_(requestGroups.begin(), requestGroups.end()),
+    maxSimultaneousDownloads_(maxSimultaneousDownloads),
+    option_(option),
+    serverStatMan_(new ServerStatMan()),
+    maxOverallDownloadSpeedLimit_
+    (option->getAsInt(PREF_MAX_OVERALL_DOWNLOAD_LIMIT)),
+    maxOverallUploadSpeedLimit_(option->getAsInt
+                                (PREF_MAX_OVERALL_UPLOAD_LIMIT)),
+    xmlRpc_(option->getAsBool(PREF_ENABLE_XML_RPC)),
+    queueCheck_(true),
+    removedErrorResult_(0),
+    removedLastErrorResult_(downloadresultcode::FINISHED),
+    maxDownloadResult_(option->getAsInt(PREF_MAX_DOWNLOAD_RESULT))
 {}
 
 RequestGroupMan::~RequestGroupMan() {}
@@ -296,9 +297,9 @@ private:
       // ".sig".
       std::string signatureFile = group->getFirstFilePath()+".sig";
       if(sig->save(signatureFile)) {
-        logger_->notice(MSG_SIGNATURE_SAVED, signatureFile.c_str());
+        A2_LOG_NOTICE(fmt(MSG_SIGNATURE_SAVED, signatureFile.c_str()));
       } else {
-        logger_->notice(MSG_SIGNATURE_NOT_SAVED, signatureFile.c_str());
+        A2_LOG_NOTICE(fmt(MSG_SIGNATURE_NOT_SAVED, signatureFile.c_str()));
       }
     }
   }
@@ -306,11 +307,11 @@ public:
   ProcessStoppedRequestGroup
   (DownloadEngine* e,
    std::deque<SharedHandle<DownloadResult> >& downloadResults,
-   std::deque<SharedHandle<RequestGroup> >& reservedGroups):
-    e_(e),
-    downloadResults_(downloadResults),
-    reservedGroups_(reservedGroups),
-    logger_(LogFactory::getInstance()) {}
+   std::deque<SharedHandle<RequestGroup> >& reservedGroups)
+    : e_(e),
+      downloadResults_(downloadResults),
+      reservedGroups_(reservedGroups)
+  {}
 
   void operator()(const SharedHandle<RequestGroup>& group)
   {
@@ -341,21 +342,21 @@ public:
           std::vector<SharedHandle<RequestGroup> > nextGroups;
           group->postDownloadProcessing(nextGroups);
           if(!nextGroups.empty()) {
-            if(logger_->debug()) {
-              logger_->debug
-                ("Adding %lu RequestGroups as a result of PostDownloadHandler.",
-                 static_cast<unsigned long>(nextGroups.size()));
-            }
+            A2_LOG_DEBUG
+              (fmt("Adding %lu RequestGroups as a result of"
+                   " PostDownloadHandler.",
+                   static_cast<unsigned long>(nextGroups.size())));
             e_->getRequestGroupMan()->insertReservedGroup(0, nextGroups);
           }
         } else {
-          logger_->notice("Download GID#%s not complete: %s",
-                          util::itos(group->getGID()).c_str(),
-                          group->getDownloadContext()->getBasePath().c_str());
+          A2_LOG_NOTICE
+            (fmt("Download GID#%s not complete: %s",
+                 util::itos(group->getGID()).c_str(),
+                 group->getDownloadContext()->getBasePath().c_str()));
           group->saveControlFile();
         }
       } catch(RecoverableException& ex) {
-        logger_->error(EX_EXCEPTION_CAUGHT, ex);
+        A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, ex);
       }
       if(group->isPauseRequested()) {
         reservedGroups_.push_front(group);
@@ -454,10 +455,8 @@ void RequestGroupMan::removeStoppedGroup(DownloadEngine* e)
 
   size_t numRemoved = numPrev-requestGroups_.size();
   if(numRemoved > 0) {
-    if(logger_->debug()) {
-      logger_->debug("%lu RequestGroup(s) deleted.",
-                     static_cast<unsigned long>(numRemoved));
-    }
+    A2_LOG_DEBUG(fmt("%lu RequestGroup(s) deleted.",
+                     static_cast<unsigned long>(numRemoved)));
   }
 }
 
@@ -521,15 +520,11 @@ void RequestGroupMan::fillRequestGroupFromReserver(DownloadEngine* e)
       util::executeHookByOptName
         (groupToAdd, e->getOption(), PREF_ON_DOWNLOAD_START);
     } catch(RecoverableException& ex) {
-      logger_->error(EX_EXCEPTION_CAUGHT, ex);
-      if(logger_->debug()) {
-        logger_->debug("Deleting temporal commands.");
-      }
+      A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, ex);
+      A2_LOG_DEBUG("Deleting temporal commands.");
       std::for_each(commands.begin(), commands.end(), Deleter());
       commands.clear();
-      if(logger_->debug()) {
-        logger_->debug("Commands deleted");
-      }
+      A2_LOG_DEBUG("Commands deleted");
       groupToAdd->releaseRuntimeResource(e);
       addDownloadResult(groupToAdd->createDownloadResult());
     }
@@ -539,9 +534,7 @@ void RequestGroupMan::fillRequestGroupFromReserver(DownloadEngine* e)
   }
   if(count > 0) {
     e->setNoWait(true);
-    if(logger_->debug()) {
-      logger_->debug("%d RequestGroup(s) added.", count);
-    }
+    A2_LOG_DEBUG(fmt("%d RequestGroup(s) added.", count));
   }
 }
 
@@ -556,7 +549,7 @@ void RequestGroupMan::save()
       try {
         (*itr)->saveControlFile();
       } catch(RecoverableException& e) {
-        logger_->error(EX_EXCEPTION_CAUGHT, e);
+        A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
       }
     }
   }
@@ -853,14 +846,15 @@ bool RequestGroupMan::loadServerStat(const std::string& filename)
 {
   std::ifstream in(filename.c_str(), std::ios::binary);
   if(!in) {
-    logger_->error(MSG_OPENING_READABLE_SERVER_STAT_FILE_FAILED, filename.c_str());
+    A2_LOG_ERROR(fmt(MSG_OPENING_READABLE_SERVER_STAT_FILE_FAILED,
+                     filename.c_str()));
     return false;
   }
   if(serverStatMan_->load(in)) {
-    logger_->notice(MSG_SERVER_STAT_LOADED, filename.c_str());
+    A2_LOG_NOTICE(fmt(MSG_SERVER_STAT_LOADED, filename.c_str()));
     return true;
   } else {
-    logger_->error(MSG_READING_SERVER_STAT_FILE_FAILED, filename.c_str());
+    A2_LOG_ERROR(fmt(MSG_READING_SERVER_STAT_FILE_FAILED, filename.c_str()));
     return false;
   }
 }
@@ -872,20 +866,20 @@ bool RequestGroupMan::saveServerStat(const std::string& filename) const
   {
     std::ofstream out(tempfile.c_str(), std::ios::binary);
     if(!out) {
-      logger_->error(MSG_OPENING_WRITABLE_SERVER_STAT_FILE_FAILED,
-                     filename.c_str());
+      A2_LOG_ERROR(fmt(MSG_OPENING_WRITABLE_SERVER_STAT_FILE_FAILED,
+                       filename.c_str()));
       return false;
     }
     if(!serverStatMan_->save(out)) {
-      logger_->error(MSG_WRITING_SERVER_STAT_FILE_FAILED, filename.c_str());
+      A2_LOG_ERROR(fmt(MSG_WRITING_SERVER_STAT_FILE_FAILED, filename.c_str()));
       return false;
     }
   }
   if(File(tempfile).renameTo(filename)) {
-    logger_->notice(MSG_SERVER_STAT_SAVED, filename.c_str());
+    A2_LOG_NOTICE(fmt(MSG_SERVER_STAT_SAVED, filename.c_str()));
     return true;
   } else {
-    logger_->error(MSG_WRITING_SERVER_STAT_FILE_FAILED, filename.c_str());
+    A2_LOG_ERROR(fmt(MSG_WRITING_SERVER_STAT_FILE_FAILED, filename.c_str()));
     return false;
   }
 }
diff --git a/src/RequestGroupMan.h b/src/RequestGroupMan.h
index dde0bb29..80e90a7f 100644
--- a/src/RequestGroupMan.h
+++ b/src/RequestGroupMan.h
@@ -51,7 +51,6 @@ namespace aria2 {
 
 class DownloadEngine;
 class Command;
-class Logger;
 struct DownloadResult;
 class ServerStatMan;
 class ServerStat;
@@ -62,7 +61,6 @@ private:
   std::deque<SharedHandle<RequestGroup> > requestGroups_;
   std::deque<SharedHandle<RequestGroup> > reservedGroups_;
   std::deque<SharedHandle<DownloadResult> > downloadResults_;
-  Logger* logger_;
   unsigned int maxSimultaneousDownloads_;
 
   const Option* option_;
diff --git a/src/SeedCheckCommand.cc b/src/SeedCheckCommand.cc
index 2ec138eb..e95c5079 100644
--- a/src/SeedCheckCommand.cc
+++ b/src/SeedCheckCommand.cc
@@ -37,9 +37,11 @@
 #include "BtRuntime.h"
 #include "PieceStorage.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "SeedCriteria.h"
 #include "message.h"
 #include "RequestGroup.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -48,11 +50,11 @@ SeedCheckCommand::SeedCheckCommand
  RequestGroup* requestGroup,
  DownloadEngine* e,
  const SharedHandle<SeedCriteria>& seedCriteria)
-  :Command(cuid),
-   requestGroup_(requestGroup),
-   e_(e),
-   seedCriteria_(seedCriteria),
-   checkStarted_(false)
+  : Command(cuid),
+    requestGroup_(requestGroup),
+    e_(e),
+    seedCriteria_(seedCriteria),
+    checkStarted_(false)
 {
   setStatusRealtime();
   requestGroup_->increaseNumCommand();
@@ -78,7 +80,7 @@ bool SeedCheckCommand::execute() {
   }
   if(checkStarted_) {
     if(seedCriteria_->evaluate()) {
-      getLogger()->notice(MSG_SEEDING_END);
+      A2_LOG_NOTICE(MSG_SEEDING_END);
       btRuntime_->setHalt(true);
     }
   }
diff --git a/src/SegmentMan.cc b/src/SegmentMan.cc
index bc668145..e75226a5 100644
--- a/src/SegmentMan.cc
+++ b/src/SegmentMan.cc
@@ -52,6 +52,7 @@
 #include "Piece.h"
 #include "FileEntry.h"
 #include "wallclock.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -61,17 +62,17 @@ SegmentEntry::SegmentEntry(cuid_t cuid, const SharedHandle<Segment>& segment)
 
 SegmentEntry::~SegmentEntry() {}
 
-SegmentMan::SegmentMan(const Option* option,
-                       const SharedHandle<DownloadContext>& downloadContext,
-                       const PieceStorageHandle& pieceStorage):
-  option_(option),
-  logger_(LogFactory::getInstance()),
-  downloadContext_(downloadContext),
-  pieceStorage_(pieceStorage),
-  lastPeerStatDlspdMapUpdated_(0),
-  cachedDlspd_(0),
-  ignoreBitfield_(downloadContext->getPieceLength(),
-                  downloadContext->getTotalLength())
+SegmentMan::SegmentMan
+(const Option* option,
+ const SharedHandle<DownloadContext>& downloadContext,
+ const PieceStorageHandle& pieceStorage)
+  : option_(option),
+    downloadContext_(downloadContext),
+    pieceStorage_(pieceStorage),
+    lastPeerStatDlspdMapUpdated_(0),
+    cachedDlspd_(0),
+    ignoreBitfield_(downloadContext->getPieceLength(),
+                    downloadContext->getTotalLength())
 {
   ignoreBitfield_.enableFilter();
 }
@@ -119,11 +120,9 @@ SharedHandle<Segment> SegmentMan::checkoutSegment
   if(!piece) {
     return SharedHandle<Segment>();
   }
-  if(logger_->debug()) {
-    logger_->debug("Attach segment#%lu to CUID#%s.",
+  A2_LOG_DEBUG(fmt("Attach segment#%lu to CUID#%s.",
                    static_cast<unsigned long>(piece->getIndex()),
-                   util::itos(cuid).c_str());
-  }
+                   util::itos(cuid).c_str()));
   SharedHandle<Segment> segment;
   if(piece->getLength() == 0) {
     segment.reset(new GrowSegment(piece));
@@ -132,24 +131,21 @@ SharedHandle<Segment> SegmentMan::checkoutSegment
   }
   SegmentEntryHandle entry(new SegmentEntry(cuid, segment));
   usedSegmentEntries_.push_back(entry);
-  if(logger_->debug()) {
-    logger_->debug("index=%lu, length=%lu, segmentLength=%lu,"
+  A2_LOG_DEBUG(fmt("index=%lu, length=%lu, segmentLength=%lu,"
                    " writtenLength=%lu",
                    static_cast<unsigned long>(segment->getIndex()),
                    static_cast<unsigned long>(segment->getLength()),
                    static_cast<unsigned long>(segment->getSegmentLength()),
-                   static_cast<unsigned long>(segment->getWrittenLength()));
-  }
+                   static_cast<unsigned long>(segment->getWrittenLength())));
   if(piece->getLength() > 0) {
     std::map<size_t, size_t>::iterator positr =
       segmentWrittenLengthMemo_.find(segment->getIndex());
     if(positr != segmentWrittenLengthMemo_.end()) {
       const size_t writtenLength = (*positr).second;
-      if(logger_->debug()) {
-        logger_->debug("writtenLength(in memo)=%lu, writtenLength=%lu",
+      A2_LOG_DEBUG(fmt("writtenLength(in memo)=%lu, writtenLength=%lu",
                        static_cast<unsigned long>(writtenLength),
-                       static_cast<unsigned long>(segment->getWrittenLength()));
-      }
+                       static_cast<unsigned long>(segment->getWrittenLength()))
+                   );
       //  If the difference between cached writtenLength and segment's
       //  writtenLength is less than one block, we assume that these
       //  missing bytes are already downloaded.
@@ -255,17 +251,13 @@ SharedHandle<Segment> SegmentMan::getCleanSegmentIfOwnerIsIdle
 
 void SegmentMan::cancelSegment(const SharedHandle<Segment>& segment)
 {
-  if(logger_->debug()) {
-    logger_->debug("Canceling segment#%lu",
-                   static_cast<unsigned long>(segment->getIndex()));
-  }
+  A2_LOG_DEBUG(fmt("Canceling segment#%lu",
+                   static_cast<unsigned long>(segment->getIndex())));
   pieceStorage_->cancelPiece(segment->getPiece());
   segmentWrittenLengthMemo_[segment->getIndex()] = segment->getWrittenLength();
-  if(logger_->debug()) {
-    logger_->debug("Memorized segment index=%lu, writtenLength=%lu",
+  A2_LOG_DEBUG(fmt("Memorized segment index=%lu, writtenLength=%lu",
                    static_cast<unsigned long>(segment->getIndex()),
-                   static_cast<unsigned long>(segment->getWrittenLength()));
-  }
+                   static_cast<unsigned long>(segment->getWrittenLength())));
 }
 
 void SegmentMan::cancelSegment(cuid_t cuid) {
@@ -472,12 +464,10 @@ size_t SegmentMan::countFreePieceFrom(size_t index) const
 
 void SegmentMan::ignoreSegmentFor(const SharedHandle<FileEntry>& fileEntry)
 {
-  if(logger_->debug()) {
-    logger_->debug("ignoring segment for path=%s, offset=%s, length=%s",
+  A2_LOG_DEBUG(fmt("ignoring segment for path=%s, offset=%s, length=%s",
                    fileEntry->getPath().c_str(),
                    util::itos(fileEntry->getOffset()).c_str(),
-                   util::uitos(fileEntry->getLength()).c_str());
-  }
+                   util::uitos(fileEntry->getLength()).c_str()));
   ignoreBitfield_.addFilter(fileEntry->getOffset(), fileEntry->getLength());
 }
 
diff --git a/src/SegmentMan.h b/src/SegmentMan.h
index 41837287..8c6e6423 100644
--- a/src/SegmentMan.h
+++ b/src/SegmentMan.h
@@ -49,7 +49,6 @@
 namespace aria2 {
 
 class Segment;
-class Logger;
 class Option;
 class PeerStat;
 class DownloadContext;
@@ -79,8 +78,6 @@ class SegmentMan {
 private:
   const Option* option_;
 
-  Logger* logger_;
-
   SharedHandle<DownloadContext> downloadContext_;
 
   SharedHandle<PieceStorage> pieceStorage_;
diff --git a/src/SelectEventPoll.cc b/src/SelectEventPoll.cc
index 4297b55e..b541631d 100644
--- a/src/SelectEventPoll.cc
+++ b/src/SelectEventPoll.cc
@@ -45,6 +45,7 @@
 #include "LogFactory.h"
 #include "Logger.h"
 #include "a2functional.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -149,7 +150,7 @@ void SelectEventPoll::AsyncNameResolverEntry::process
 
 #endif // ENABLE_ASYNC_DNS
 
-SelectEventPoll::SelectEventPoll():logger_(LogFactory::getInstance())
+SelectEventPoll::SelectEventPoll()
 {
 #ifdef __MINGW32__
   dummySocket_ = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
@@ -226,11 +227,11 @@ void SelectEventPoll::poll(const struct timeval& tv)
 
 #ifdef __MINGW32__
 namespace {
-void checkFdCountMingw(const fd_set& fdset, Logger* logger)
+void checkFdCountMingw(const fd_set& fdset)
 {
   if(fdset.fd_count >= FD_SETSIZE) {
-    logger->warn("The number of file descriptor exceeded FD_SETSIZE. "
-                 "Download may slow down or fail.");
+    A2_LOG_WARN("The number of file descriptor exceeded FD_SETSIZE. "
+                "Download may slow down or fail.");
   }
 }
 } // namespace
@@ -250,21 +251,21 @@ void SelectEventPoll::updateFdSet()
     sock_t fd = (*i)->getSocket();
 #ifndef __MINGW32__
     if(fd < 0 || FD_SETSIZE <= fd) {
-      logger_->warn("Detected file descriptor >= FD_SETSIZE or < 0. "
-                    "Download may slow down or fail.");
+      A2_LOG_WARN("Detected file descriptor >= FD_SETSIZE or < 0. "
+                  "Download may slow down or fail.");
       continue;
     }
 #endif // !__MINGW32__
     int events = (*i)->getEvents();
     if(events&EventPoll::EVENT_READ) {
 #ifdef __MINGW32__
-      checkFdCountMingw(rfdset_, logger_);
+      checkFdCountMingw(rfdset_);
 #endif // __MINGW32__
       FD_SET(fd, &rfdset_);
     }
     if(events&EventPoll::EVENT_WRITE) {
 #ifdef __MINGW32__
-      checkFdCountMingw(wfdset_, logger_);
+      checkFdCountMingw(wfdset_);
 #endif // __MINGW32__
       FD_SET(fd, &wfdset_);
     }
@@ -306,9 +307,7 @@ bool SelectEventPoll::deleteEvents(sock_t socket, Command* command,
     updateFdSet();
     return true;
   } else {
-    if(logger_->debug()) {
-      logger_->debug("Socket %d is not found in SocketEntries.", socket);
-    }
+    A2_LOG_DEBUG(fmt("Socket %d is not found in SocketEntries.", socket));
     return false;
   }
 }
diff --git a/src/SelectEventPoll.h b/src/SelectEventPoll.h
index 705d9eb9..739ccb2a 100644
--- a/src/SelectEventPoll.h
+++ b/src/SelectEventPoll.h
@@ -45,8 +45,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class SelectEventPoll : public EventPoll {
 private:
   class CommandEvent {
@@ -168,8 +166,6 @@ private:
   sock_t dummySocket_;
 #endif // __MINGW32__
 
-  Logger* logger_;
-
   void updateFdSet();
 public:
   SelectEventPoll();
diff --git a/src/ServerStat.cc b/src/ServerStat.cc
index a73771b8..c841059a 100644
--- a/src/ServerStat.cc
+++ b/src/ServerStat.cc
@@ -38,7 +38,9 @@
 #include <algorithm>
 
 #include "array_fun.h"
+#include "Logger.h"
 #include "LogFactory.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -48,15 +50,13 @@ const std::string ServerStat::STATUS_STRING[] = {
 };
 
 ServerStat::ServerStat(const std::string& hostname, const std::string& protocol)
-  :
-  hostname_(hostname),
-  protocol_(protocol),
-  downloadSpeed_(0),
-  singleConnectionAvgSpeed_(0),
-  multiConnectionAvgSpeed_(0),
-  counter_(0),
-  logger_(LogFactory::getInstance()),
-  status_(OK)
+  : hostname_(hostname),
+    protocol_(protocol),
+    downloadSpeed_(0),
+    singleConnectionAvgSpeed_(0),
+    multiConnectionAvgSpeed_(0),
+    counter_(0),
+    status_(OK)
 {}
 
 ServerStat::~ServerStat() {}
@@ -101,20 +101,17 @@ void ServerStat::updateSingleConnectionAvgSpeed(unsigned int downloadSpeed)
       ((1.0/5.0)*(float)downloadSpeed);
   }
   if(avgDownloadSpeed < (int)(0.80*singleConnectionAvgSpeed_)) {
-    if(logger_->debug()) {
-      logger_->debug("ServerStat:%s: resetting counter since single connection"
-                     " speed dropped", getHostname().c_str());
-    }
+    A2_LOG_DEBUG(fmt("ServerStat:%s: resetting counter since single connection"
+                     " speed dropped",
+                     getHostname().c_str()));
     counter_ = 0;
   }
-  if(logger_->debug()) {
-    logger_->debug("ServerStat:%s: singleConnectionAvgSpeed_ old:%.2fKB/s"
+  A2_LOG_DEBUG(fmt("ServerStat:%s: singleConnectionAvgSpeed_ old:%.2fKB/s"
                    " new:%.2fKB/s last:%.2fKB/s",
                    getHostname().c_str(),
                    (float) singleConnectionAvgSpeed_/1024,
                    (float) avgDownloadSpeed/1024,
-                   (float) downloadSpeed / 1024);
-  }
+                   (float) downloadSpeed / 1024));
   singleConnectionAvgSpeed_ = (int)avgDownloadSpeed;
 }
 
@@ -138,14 +135,12 @@ void ServerStat::updateMultiConnectionAvgSpeed(unsigned int downloadSpeed)
     avgDownloadSpeed = ((4.0/5.0)*(float)multiConnectionAvgSpeed_) +
       ((1.0/5.0)*(float)downloadSpeed);
   }
-  if(logger_->debug()) {
-    logger_->debug("ServerStat:%s: multiConnectionAvgSpeed_ old:%.2fKB/s"
+  A2_LOG_DEBUG(fmt("ServerStat:%s: multiConnectionAvgSpeed_ old:%.2fKB/s"
                    " new:%.2fKB/s last:%.2fKB/s",
                    getHostname().c_str(),
                    (float) multiConnectionAvgSpeed_/1024,
                    (float) avgDownloadSpeed/1024,
-                   (float) downloadSpeed / 1024);
-  }
+                   (float) downloadSpeed / 1024));
   multiConnectionAvgSpeed_ = (int)avgDownloadSpeed;
 }
 
@@ -176,11 +171,10 @@ void ServerStat::setStatus(const std::string& status)
 
 void ServerStat::setStatusInternal(STATUS status)
 {
-  if(logger_->debug()) {
-    logger_->debug("ServerStat: set status %s for %s (%s)",
+  A2_LOG_DEBUG(fmt("ServerStat: set status %s for %s (%s)",
                    STATUS_STRING[status].c_str(),
-                   hostname_.c_str(), protocol_.c_str());
-  }
+                   hostname_.c_str(),
+                   protocol_.c_str()));
   status_ = status;
   lastUpdated_.reset();
 }
diff --git a/src/ServerStat.h b/src/ServerStat.h
index 8cb699d9..f572997a 100644
--- a/src/ServerStat.h
+++ b/src/ServerStat.h
@@ -43,8 +43,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 // ServerStatMan: has many ServerStat
 // URISelector: interface
 // ServerStatURISelector: Has a reference of ServerStatMan
@@ -160,8 +158,6 @@ private:
 
   unsigned int counter_;
 
-  Logger* logger_;
-
   STATUS status_;
 
   Time lastUpdated_;
diff --git a/src/SimpleBtMessage.cc b/src/SimpleBtMessage.cc
index e542b37e..eb93384f 100644
--- a/src/SimpleBtMessage.cc
+++ b/src/SimpleBtMessage.cc
@@ -37,12 +37,15 @@
 #include "Peer.h"
 #include "PeerConnection.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-SimpleBtMessage::SimpleBtMessage(uint8_t id, const std::string& name):
-  AbstractBtMessage(id, name) {}
+SimpleBtMessage::SimpleBtMessage(uint8_t id, const std::string& name)
+  : AbstractBtMessage(id, name)
+{}
 
 void SimpleBtMessage::send() {
   if(isInvalidate()) {
@@ -52,19 +55,15 @@ void SimpleBtMessage::send() {
     return;
   }
   if(!isSendingInProgress()) {
-    if(getLogger()->info()) {
-      getLogger()->info(MSG_SEND_PEER_MESSAGE,
-                        util::itos(getCuid()).c_str(),
-                        getPeer()->getIPAddress().c_str(),
-                        getPeer()->getPort(),
-                        toString().c_str());
-    }
+    A2_LOG_INFO(fmt(MSG_SEND_PEER_MESSAGE,
+                    util::itos(getCuid()).c_str(),
+                    getPeer()->getIPAddress().c_str(),
+                    getPeer()->getPort(),
+                    toString().c_str()));
     unsigned char* msg = createMessage();
     size_t msgLength = getMessageLength();
-    if(getLogger()->debug()) {
-      getLogger()->debug("msglength = %lu bytes",
-                         static_cast<unsigned long>(msgLength));
-    }
+    A2_LOG_DEBUG(fmt("msglength = %lu bytes",
+                     static_cast<unsigned long>(msgLength)));
     getPeerConnection()->pushBytes(msg, msgLength);
   }
   getPeerConnection()->sendPendingData();
diff --git a/src/SimpleLogFormatter.cc b/src/SimpleLogFormatter.cc
deleted file mode 100644
index f15557a1..00000000
--- a/src/SimpleLogFormatter.cc
+++ /dev/null
@@ -1,96 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2010 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#include "SimpleLogFormatter.h"
-
-#include <cassert>
-#include <ostream>
-
-#include "util.h"
-#include "a2time.h"
-#include "A2STR.h"
-#include "StringFormat.h"
-#include "Exception.h"
-
-namespace aria2 {
-
-SimpleLogFormatter::SimpleLogFormatter() {}
-
-SimpleLogFormatter::~SimpleLogFormatter() {}
-
-namespace {
-void writeHeader
-(std::ostream& o, const std::string& date, const std::string& logLevelLabel)
-{
-  o << StringFormat("%s %s - ", date.c_str(), logLevelLabel.c_str());
-}
-} // namespace
-
-void SimpleLogFormatter::writeLog
-(std::ostream& o, Logger::LEVEL level, const std::string& logLevelLabel,
- const char* msg, va_list ap)
-{
-  struct timeval tv;
-  gettimeofday(&tv, 0);
-  char datestr[27]; // 'YYYY-MM-DD hh:mm:ss.uuuuuu'+'\0' = 27 bytes
-  struct tm tm;
-  //tv.tv_sec may not be of type time_t.
-  time_t timesec = tv.tv_sec;
-  localtime_r(&timesec, &tm);
-  size_t dateLength =
-    strftime(datestr, sizeof(datestr), "%Y-%m-%d %H:%M:%S", &tm);
-  assert(dateLength <= (size_t)20);
-  snprintf(datestr+dateLength, sizeof(datestr)-dateLength,
-           ".%06ld", tv.tv_usec);
-  writeHeader(o, datestr, logLevelLabel);
-  {
-    char buf[1024];
-    std::string body = util::replace(msg, A2STR::CR_C, A2STR::NIL);
-    body += A2STR::LF_C;
-    if(vsnprintf(buf, sizeof(buf), body.c_str(), ap) < 0) {
-      o << "SimpleLogger error, failed to format message.\n";
-    } else {
-      o << buf;
-    }
-  }
-}
-
-void SimpleLogFormatter::writeStackTrace
-(std::ostream& o, Logger::LEVEL level, const std::string& logLevelLabel,
- const Exception& e)
-{
-  o << e.stackTrace();
-}
-
-} // namespace aria2
diff --git a/src/SingleFileAllocationIterator.cc b/src/SingleFileAllocationIterator.cc
index 96d91f76..420ff699 100644
--- a/src/SingleFileAllocationIterator.cc
+++ b/src/SingleFileAllocationIterator.cc
@@ -49,12 +49,13 @@ namespace aria2 {
 #define ALIGNMENT 512
 
 SingleFileAllocationIterator::SingleFileAllocationIterator
-(BinaryStream* stream, off_t offset, uint64_t totalLength):
-  stream_(stream),
-  offset_(offset),
-  totalLength_(totalLength),
-  buffer_(0),
-  logger_(LogFactory::getInstance())
+(BinaryStream* stream,
+ off_t offset,
+ uint64_t totalLength)
+  : stream_(stream),
+    offset_(offset),
+    totalLength_(totalLength),
+    buffer_(0)
 {
   if(offset_%ALIGNMENT != 0) {
     stream_->disableDirectIO();
@@ -75,9 +76,9 @@ void SingleFileAllocationIterator::init()
   static bool noticeDone = false;
   if(!noticeDone) {
     noticeDone = true;
-    logger_->notice("Allocating disk space. Use --file-allocation=none to"
-                    " disable it. See --file-allocation option in man page for"
-                    " more details.");
+    A2_LOG_NOTICE("Allocating disk space. Use --file-allocation=none to"
+                  " disable it. See --file-allocation option in man page for"
+                  " more details.");
   }
 #ifdef HAVE_POSIX_MEMALIGN
   buffer_ = reinterpret_cast<unsigned char*>
diff --git a/src/SingleFileAllocationIterator.h b/src/SingleFileAllocationIterator.h
index 68cc57cc..a3d12602 100644
--- a/src/SingleFileAllocationIterator.h
+++ b/src/SingleFileAllocationIterator.h
@@ -40,7 +40,6 @@
 namespace aria2 {
 
 class BinaryStream;
-class Logger;
 
 class SingleFileAllocationIterator:public FileAllocationIterator
 {
@@ -52,8 +51,6 @@ private:
   uint64_t totalLength_;
 
   unsigned char* buffer_;
-
-  Logger* logger_;
 public:
   SingleFileAllocationIterator(BinaryStream* stream, off_t offset, uint64_t totalLength);
 
diff --git a/src/SocketCore.cc b/src/SocketCore.cc
index f735ec01..95cc5e96 100644
--- a/src/SocketCore.cc
+++ b/src/SocketCore.cc
@@ -50,6 +50,7 @@
 #include "DlRetryEx.h"
 #include "DlAbortEx.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "util.h"
 #include "TimeA2.h"
 #include "a2functional.h"
@@ -130,11 +131,17 @@ void SocketCore::setTLSContext(const SharedHandle<TLSContext>& tlsContext)
 }
 #endif // ENABLE_SSL
 
-SocketCore::SocketCore(int sockType):sockType_(sockType), sockfd_(-1)  {
+SocketCore::SocketCore(int sockType)
+  : sockType_(sockType),
+    sockfd_(-1)
+{
   init();
 }
 
-SocketCore::SocketCore(sock_t sockfd, int sockType):sockType_(sockType), sockfd_(sockfd) {
+SocketCore::SocketCore(sock_t sockfd, int sockType)
+  : sockType_(sockType),
+    sockfd_(sockfd)
+{
   init();
 }
 
@@ -431,9 +438,7 @@ void SocketCore::establishConnection(const std::string& host, uint16_t port)
                   (*i).second) == -1) {
           errNum = SOCKET_ERRNO;
           error = errorMsg(errNum);
-          if(LogFactory::getInstance()->debug()) {
-            LogFactory::getInstance()->debug(EX_SOCKET_BIND, error.c_str());
-          }
+          A2_LOG_DEBUG(fmt(EX_SOCKET_BIND, error.c_str()));
         } else {
           bindSuccess = true;
           break;
@@ -1274,9 +1279,7 @@ void SocketCore::bindAddress(const std::string& iface)
                       host, NI_MAXHOST, 0, 0,
                       NI_NUMERICHOST);
       if(s == 0) {
-        if(LogFactory::getInstance()->debug()) {
-          LogFactory::getInstance()->debug("Sockets will bind to %s", host);
-        }
+        A2_LOG_DEBUG(fmt("Sockets will bind to %s", host));
       }
     }
   }
@@ -1286,17 +1289,14 @@ void getInterfaceAddress
 (std::vector<std::pair<struct sockaddr_storage, socklen_t> >& ifAddrs,
  const std::string& iface, int family, int aiFlags)
 {
-  Logger* logger = LogFactory::getInstance();
-  if(logger->debug()) {
-    logger->debug("Finding interface %s", iface.c_str());
-  }
+  A2_LOG_DEBUG(fmt("Finding interface %s", iface.c_str()));
 #ifdef HAVE_GETIFADDRS
   // First find interface in interface addresses
   struct ifaddrs* ifaddr = 0;
   if(getifaddrs(&ifaddr) == -1) {
     int errNum = SOCKET_ERRNO;
-    logger->info(MSG_INTERFACE_NOT_FOUND,
-                 iface.c_str(), errorMsg(errNum).c_str());
+    A2_LOG_INFO(fmt(MSG_INTERFACE_NOT_FOUND,
+                    iface.c_str(), errorMsg(errNum).c_str()));
   } else {
     auto_delete<struct ifaddrs*> ifaddrDeleter(ifaddr, freeifaddrs);
     for(struct ifaddrs* ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
@@ -1335,7 +1335,7 @@ void getInterfaceAddress
     int s;
     s = callGetaddrinfo(&res, iface.c_str(), 0, family, SOCK_STREAM, aiFlags,0);
     if(s) {
-      logger->info(MSG_INTERFACE_NOT_FOUND, iface.c_str(), gai_strerror(s));
+      A2_LOG_INFO(fmt(MSG_INTERFACE_NOT_FOUND, iface.c_str(), gai_strerror(s)));
     } else {
       WSAAPI_AUTO_DELETE<struct addrinfo*> resDeleter(res, freeaddrinfo);
       struct addrinfo* rp;
diff --git a/src/TimedHaltCommand.cc b/src/TimedHaltCommand.cc
index ab36a110..1962b812 100644
--- a/src/TimedHaltCommand.cc
+++ b/src/TimedHaltCommand.cc
@@ -36,15 +36,19 @@
 #include "DownloadEngine.h"
 #include "RequestGroupMan.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "message.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-TimedHaltCommand::TimedHaltCommand(cuid_t cuid, DownloadEngine* e,
-                                   time_t secondsToHalt,
-                                   bool forceHalt):
-  TimeBasedCommand(cuid, e, secondsToHalt, true),
-  forceHalt_(forceHalt) {}
+TimedHaltCommand::TimedHaltCommand
+(cuid_t cuid, DownloadEngine* e,
+ time_t secondsToHalt,
+ bool forceHalt)
+  : TimeBasedCommand(cuid, e, secondsToHalt, true),
+    forceHalt_(forceHalt)
+{}
 
 TimedHaltCommand::~TimedHaltCommand() {}
 
@@ -59,10 +63,10 @@ void TimedHaltCommand::preProcess()
 void TimedHaltCommand::process()
 {
   if(!getDownloadEngine()->isHaltRequested()) {
-    getLogger()->notice(MSG_TIME_HAS_PASSED,
-                        static_cast<long int>(getInterval()));
+    A2_LOG_NOTICE(fmt(MSG_TIME_HAS_PASSED,
+                      static_cast<long int>(getInterval())));
     if(forceHalt_) {
-      getLogger()->notice("This is emergency shutdown.");
+      A2_LOG_NOTICE("This is emergency shutdown.");
       getDownloadEngine()->requestForceHalt();
     } else {
       getDownloadEngine()->requestHalt();
diff --git a/src/TrackerWatcherCommand.cc b/src/TrackerWatcherCommand.cc
index e20bcf88..6cd07c62 100644
--- a/src/TrackerWatcherCommand.cc
+++ b/src/TrackerWatcherCommand.cc
@@ -53,6 +53,7 @@
 #include "Option.h"
 #include "DlAbortEx.h"
 #include "Logger.h"
+#include "LogFactory.h"
 #include "A2STR.h"
 #include "SocketCore.h"
 #include "Request.h"
@@ -61,14 +62,15 @@
 #include "bittorrent_helper.h"
 #include "a2functional.h"
 #include "util.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 TrackerWatcherCommand::TrackerWatcherCommand
-(cuid_t cuid, RequestGroup* requestGroup, DownloadEngine* e):
-  Command(cuid),
-  requestGroup_(requestGroup),
-  e_(e)
+(cuid_t cuid, RequestGroup* requestGroup, DownloadEngine* e)
+  : Command(cuid),
+    requestGroup_(requestGroup),
+    e_(e)
 {
   requestGroup_->increaseNumCommand();
 }
@@ -92,9 +94,7 @@ bool TrackerWatcherCommand::execute() {
     }
   }
   if(btAnnounce_->noMoreAnnounce()) {
-    if(getLogger()->debug()) {
-      getLogger()->debug("no more announce");
-    }
+    A2_LOG_DEBUG("no more announce");
     return true;
   }
   if(!trackerRequestGroup_) {
@@ -106,11 +106,9 @@ bool TrackerWatcherCommand::execute() {
         trackerRequestGroup_->createInitialCommand(*commands, e_);
         e_->addCommand(*commands);
         commands->clear();
-        if(getLogger()->debug()) {
-          getLogger()->debug("added tracker request command");
-        }
+        A2_LOG_DEBUG("added tracker request command");
       } catch(RecoverableException& ex) {
-        getLogger()->error(EX_EXCEPTION_CAUGHT, ex);
+        A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, ex);
       }
     }
   } else if(trackerRequestGroup_->downloadFinished()){
@@ -121,7 +119,7 @@ bool TrackerWatcherCommand::execute() {
       btAnnounce_->announceSuccess();
       btAnnounce_->resetAnnounce();
     } catch(RecoverableException& ex) {
-      getLogger()->error(EX_EXCEPTION_CAUGHT, ex);      
+      A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, ex);      
       btAnnounce_->announceFailure();
       if(btAnnounce_->isAllAnnounceFailed()) {
         btAnnounce_->resetAnnounce();
@@ -176,11 +174,9 @@ void TrackerWatcherCommand::processTrackerResponse
     command->setPeerStorage(peerStorage_);
     command->setPieceStorage(pieceStorage_);
     e_->addCommand(command);
-    if(getLogger()->debug()) {
-      getLogger()->debug("CUID#%s - Adding new command CUID#%s",
-                         util::itos(getCuid()).c_str(),
-                         util::itos(peer->usedBy()).c_str());
-    }
+    A2_LOG_DEBUG(fmt("CUID#%s - Adding new command CUID#%s",
+                     util::itos(getCuid()).c_str(),
+                     util::itos(peer->usedBy()).c_str()));
   }
 }
 
@@ -220,13 +216,9 @@ TrackerWatcherCommand::createRequestGroup(const std::string& uri)
   uris.push_back(uri);
   SharedHandle<RequestGroup> rg(new RequestGroup(getOption()));
   if(backupTrackerIsAvailable(requestGroup_->getDownloadContext())) {
-    if(getLogger()->debug()) {
-      getLogger()->debug("This is multi-tracker announce.");
-    }
+    A2_LOG_DEBUG("This is multi-tracker announce.");
   } else {
-    if(getLogger()->debug()) {
-      getLogger()->debug("This is single-tracker announce.");
-    }
+    A2_LOG_DEBUG("This is single-tracker announce.");
   }
   rg->setNumConcurrentCommand(1);
   // If backup tracker is available, try 2 times for each tracker
@@ -254,10 +246,8 @@ TrackerWatcherCommand::createRequestGroup(const std::string& uri)
   rg->setFileAllocationEnabled(false);
   rg->setPreLocalFileCheckEnabled(false);
   util::removeMetalinkContentTypes(rg);
-  if(getLogger()->info()) {
-    getLogger()->info("Creating tracker request group GID#%s",
-                      util::itos(rg->getGID()).c_str());
-  }
+  A2_LOG_INFO(fmt("Creating tracker request group GID#%s",
+                  util::itos(rg->getGID()).c_str()));
   return rg;
 }
 
diff --git a/src/UTMetadataDataExtensionMessage.cc b/src/UTMetadataDataExtensionMessage.cc
index 75166108..93cf0a62 100644
--- a/src/UTMetadataDataExtensionMessage.cc
+++ b/src/UTMetadataDataExtensionMessage.cc
@@ -45,15 +45,18 @@
 #include "bittorrent_helper.h"
 #include "DiskAdaptor.h"
 #include "Piece.h"
+#include "Logger.h"
 #include "LogFactory.h"
 #include "DlAbortEx.h"
+#include "fmt.h"
 
 namespace aria2 {
 
 UTMetadataDataExtensionMessage::UTMetadataDataExtensionMessage
-(uint8_t extensionMessageID):UTMetadataExtensionMessage(extensionMessageID),
-                             tracker_(0),
-                             logger_(LogFactory::getInstance()) {}
+(uint8_t extensionMessageID)
+  : UTMetadataExtensionMessage(extensionMessageID),
+    tracker_(0)
+{}
 
 UTMetadataDataExtensionMessage::~UTMetadataDataExtensionMessage() {}
 
@@ -74,10 +77,8 @@ std::string UTMetadataDataExtensionMessage::toString() const
 void UTMetadataDataExtensionMessage::doReceivedAction()
 {
   if(tracker_->tracks(getIndex())) {
-    if(logger_->debug()) {
-      logger_->debug("ut_metadata index=%lu found in tracking list",
-                     static_cast<unsigned long>(getIndex()));
-    }
+    A2_LOG_DEBUG(fmt("ut_metadata index=%lu found in tracking list",
+                     static_cast<unsigned long>(getIndex())));
     tracker_->remove(getIndex());
     pieceStorage_->getDiskAdaptor()->writeData
       (reinterpret_cast<const unsigned char*>(data_.c_str()), data_.size(),
@@ -91,9 +92,9 @@ void UTMetadataDataExtensionMessage::doReceivedAction()
                                   metadata.data(), metadata.size());
       if(memcmp(infoHash, bittorrent::getInfoHash(dctx_),
                 INFO_HASH_LENGTH) == 0) {
-        logger_->info("Got ut_metadata");
+        A2_LOG_INFO("Got ut_metadata");
       } else {
-        logger_->info("Got wrong ut_metadata");
+        A2_LOG_INFO("Got wrong ut_metadata");
         for(size_t i = 0; i < dctx_->getNumPieces(); ++i) {
           pieceStorage_->markPieceMissing(i);
         }
@@ -101,10 +102,8 @@ void UTMetadataDataExtensionMessage::doReceivedAction()
       }
     }
   } else {
-    if(logger_->debug()) {
-      logger_->debug("ut_metadata index=%lu is not tracked",
-                     static_cast<unsigned long>(getIndex()));
-    }
+    A2_LOG_DEBUG(fmt("ut_metadata index=%lu is not tracked",
+                     static_cast<unsigned long>(getIndex())));
   }
 }
 
diff --git a/src/UTMetadataDataExtensionMessage.h b/src/UTMetadataDataExtensionMessage.h
index e4a70862..bd5b947c 100644
--- a/src/UTMetadataDataExtensionMessage.h
+++ b/src/UTMetadataDataExtensionMessage.h
@@ -42,7 +42,6 @@ namespace aria2 {
 class DownloadContext;
 class PieceStorage;
 class UTMetadataRequestTracker;
-class Logger;
 
 class UTMetadataDataExtensionMessage:public UTMetadataExtensionMessage {
 private:
@@ -55,8 +54,6 @@ private:
   SharedHandle<PieceStorage> pieceStorage_;
 
   UTMetadataRequestTracker* tracker_;
-
-  Logger* logger_;
 public:
   UTMetadataDataExtensionMessage(uint8_t extensionMessageID);
 
diff --git a/src/UTMetadataPostDownloadHandler.cc b/src/UTMetadataPostDownloadHandler.cc
index a7f72aa0..3dd9329d 100644
--- a/src/UTMetadataPostDownloadHandler.cc
+++ b/src/UTMetadataPostDownloadHandler.cc
@@ -49,6 +49,7 @@
 #include "message.h"
 #include "prefs.h"
 #include "Option.h"
+#include "fmt.h"
 
 namespace aria2 {
 
@@ -66,8 +67,7 @@ bool UTMetadataPostDownloadHandler::Criteria::match
   return false;
 }
 
-UTMetadataPostDownloadHandler::UTMetadataPostDownloadHandler():
-  logger_(LogFactory::getInstance())
+UTMetadataPostDownloadHandler::UTMetadataPostDownloadHandler()
 {
   SharedHandle<Criteria> cri(new Criteria());
   setCriteria(cri);
@@ -87,9 +87,9 @@ void UTMetadataPostDownloadHandler::getNextRequestGroups
       util::applyDir(requestGroup->getOption()->get(PREF_DIR),
                      util::toHex(attrs->infoHash)+".torrent");
     if(util::saveAs(filename, torrent)) {
-      logger_->notice(MSG_METADATA_SAVED, filename.c_str());
+      A2_LOG_NOTICE(fmt(MSG_METADATA_SAVED, filename.c_str()));
     } else {
-      logger_->notice(MSG_METADATA_NOT_SAVED, filename.c_str());
+      A2_LOG_NOTICE(fmt(MSG_METADATA_NOT_SAVED, filename.c_str()));
     }
   }
   if(!requestGroup->getOption()->getAsBool(PREF_BT_METADATA_ONLY)) {
diff --git a/src/UTMetadataPostDownloadHandler.h b/src/UTMetadataPostDownloadHandler.h
index 0e8293ef..19364304 100644
--- a/src/UTMetadataPostDownloadHandler.h
+++ b/src/UTMetadataPostDownloadHandler.h
@@ -40,13 +40,9 @@
 
 namespace aria2 {
 
-class Logger;
-
 class UTMetadataPostDownloadHandler:public PostDownloadHandler
 {
 private:
-  Logger* logger_;
-
   class Criteria:public RequestGroupCriteria
   {
   public:
diff --git a/src/UTMetadataRequestFactory.cc b/src/UTMetadataRequestFactory.cc
index 40130b55..604449cf 100644
--- a/src/UTMetadataRequestFactory.cc
+++ b/src/UTMetadataRequestFactory.cc
@@ -41,15 +41,17 @@
 #include "UTMetadataRequestExtensionMessage.h"
 #include "UTMetadataRequestTracker.h"
 #include "BtMessage.h"
+#include "Logger.h"
 #include "LogFactory.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-UTMetadataRequestFactory::UTMetadataRequestFactory():
-  dispatcher_(0),
-  messageFactory_(0),
-  tracker_(0),
-  logger_(LogFactory::getInstance()) {}
+UTMetadataRequestFactory::UTMetadataRequestFactory()
+  : dispatcher_(0),
+    messageFactory_(0),
+    tracker_(0)
+{}
 
 void UTMetadataRequestFactory::create
 (std::vector<SharedHandle<BtMessage> >& msgs, size_t num,
@@ -60,16 +62,12 @@ void UTMetadataRequestFactory::create
     SharedHandle<Piece> p =
       pieceStorage->getMissingPiece(peer_, metadataRequests);
     if(!p) {
-      if(logger_->debug()) {
-        logger_->debug("No ut_metadata piece is available to download.");
-      }
+      A2_LOG_DEBUG("No ut_metadata piece is available to download.");
       break;
     }
     --num;
-    if(logger_->debug()) {
-      logger_->debug("Creating ut_metadata request index=%lu",
-                     static_cast<unsigned long>(p->getIndex()));
-    }
+    A2_LOG_DEBUG(fmt("Creating ut_metadata request index=%lu",
+                     static_cast<unsigned long>(p->getIndex())));
     SharedHandle<UTMetadataRequestExtensionMessage> m
       (new UTMetadataRequestExtensionMessage
        (peer_->getExtensionMessageID("ut_metadata")));
diff --git a/src/UTMetadataRequestFactory.h b/src/UTMetadataRequestFactory.h
index a97fda98..e8e02b2a 100644
--- a/src/UTMetadataRequestFactory.h
+++ b/src/UTMetadataRequestFactory.h
@@ -50,7 +50,6 @@ class BtMessageDispatcher;
 class BtMessageFactory;
 class UTMetadataRequestTracker;
 class BtMessage;
-class Logger;
 
 class UTMetadataRequestFactory {
 private:
@@ -63,8 +62,6 @@ private:
   BtMessageFactory* messageFactory_;
 
   UTMetadataRequestTracker* tracker_;
-
-  Logger* logger_;
 public:
   UTMetadataRequestFactory();
 
diff --git a/src/UTMetadataRequestTracker.cc b/src/UTMetadataRequestTracker.cc
index 4c35e81b..d04887dc 100644
--- a/src/UTMetadataRequestTracker.cc
+++ b/src/UTMetadataRequestTracker.cc
@@ -36,12 +36,13 @@
 
 #include <algorithm>
 
+#include "Logger.h"
 #include "LogFactory.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-UTMetadataRequestTracker::UTMetadataRequestTracker():
-  logger_(LogFactory::getInstance()) {}
+UTMetadataRequestTracker::UTMetadataRequestTracker() {}
 
 void UTMetadataRequestTracker::add(size_t index)
 {
@@ -71,10 +72,8 @@ std::vector<size_t> UTMetadataRequestTracker::removeTimeoutEntry()
   for(std::vector<RequestEntry>::iterator i = trackedRequests_.begin(),
         eoi = trackedRequests_.end(); i != eoi;) {
     if((*i).elapsed(TIMEOUT)) {
-      if(logger_->debug()) {
-        logger_->debug("ut_metadata request timeout. index=%lu",
-                       static_cast<unsigned long>((*i).index_));
-      }
+      A2_LOG_DEBUG(fmt("ut_metadata request timeout. index=%lu",
+                       static_cast<unsigned long>((*i).index_)));
       indexes.push_back((*i).index_);
       i = trackedRequests_.erase(i);
       eoi = trackedRequests_.end();
diff --git a/src/UTMetadataRequestTracker.h b/src/UTMetadataRequestTracker.h
index fbd93770..5ba719b5 100644
--- a/src/UTMetadataRequestTracker.h
+++ b/src/UTMetadataRequestTracker.h
@@ -44,8 +44,6 @@
 
 namespace aria2 {
 
-class Logger;
-
 class UTMetadataRequestTracker {
 private:
   struct RequestEntry {
@@ -66,8 +64,6 @@ private:
   };
 
   std::vector<RequestEntry> trackedRequests_;
-
-  Logger* logger_;
 public:
   UTMetadataRequestTracker();
 
diff --git a/src/XmlRpcMethod.cc b/src/XmlRpcMethod.cc
index 152aef70..be243d05 100644
--- a/src/XmlRpcMethod.cc
+++ b/src/XmlRpcMethod.cc
@@ -46,15 +46,16 @@
 #include "XmlRpcResponse.h"
 #include "prefs.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "DlAbortEx.h"
 
 namespace aria2 {
 
 namespace xmlrpc {
 
-XmlRpcMethod::XmlRpcMethod():
-  optionParser_(OptionParser::getInstance()),
-  logger_(LogFactory::getInstance()) {}
+XmlRpcMethod::XmlRpcMethod()
+  : optionParser_(OptionParser::getInstance())
+{}
 
 XmlRpcMethod::~XmlRpcMethod() {}
 
@@ -73,9 +74,7 @@ XmlRpcResponse XmlRpcMethod::execute
   try {
     return XmlRpcResponse(0, process(req, e));
   } catch(RecoverableException& e) {
-    if(logger_->debug()) {
-      logger_->debug(EX_EXCEPTION_CAUGHT, e);
-    }
+    A2_LOG_DEBUG_EX(EX_EXCEPTION_CAUGHT, e);
     return XmlRpcResponse(1, createErrorResponse(e));
   }
 }
diff --git a/src/XmlRpcMethod.h b/src/XmlRpcMethod.h
index 3a875ed6..cbdf65c1 100644
--- a/src/XmlRpcMethod.h
+++ b/src/XmlRpcMethod.h
@@ -46,7 +46,6 @@ namespace aria2 {
 
 class DownloadEngine;
 class OptionParser;
-class Logger;
 class Option;
 class Exception;
 
@@ -65,8 +64,6 @@ struct XmlRpcResponse;
 class XmlRpcMethod {
 private:
   SharedHandle<OptionParser> optionParser_;
-
-  Logger* logger_;
 protected:
   // Subclass must implement this function to fulfil XmlRpcRequest
   // req.  The return value of this method is used as a return value
diff --git a/src/XmlRpcMethodImpl.cc b/src/XmlRpcMethodImpl.cc
index efad911c..70a6e839 100644
--- a/src/XmlRpcMethodImpl.cc
+++ b/src/XmlRpcMethodImpl.cc
@@ -49,6 +49,7 @@
 #include "util.h"
 #include "RequestGroupMan.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "XmlRpcRequest.h"
 #include "PieceStorage.h"
 #include "DownloadContext.h"
@@ -1273,7 +1274,7 @@ SharedHandle<ValueBase> goingShutdown
   // Schedule shutdown after 3seconds to give time to client to
   // receive XML-RPC response.
   e->addRoutineCommand(new TimedHaltCommand(e->newCUID(), e, 3, forceHalt));
-  LogFactory::getInstance()->info("Scheduled shutdown in 3 seconds.");
+  A2_LOG_INFO("Scheduled shutdown in 3 seconds.");
   return VLB_OK;
 }
 } // namespace
diff --git a/src/download_helper.cc b/src/download_helper.cc
index 1f2a11e6..4d313085 100644
--- a/src/download_helper.cc
+++ b/src/download_helper.cc
@@ -52,6 +52,7 @@
 #include "DlAbortEx.h"
 #include "message.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "FileEntry.h"
 #include "LogFactory.h"
 #include "File.h"
@@ -401,7 +402,7 @@ public:
       } catch(RecoverableException& e) {
         // error occurred while parsing torrent file.
         // We simply ignore it. 
-        LogFactory::getInstance()->error(EX_EXCEPTION_CAUGHT, e);
+        A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
       }
     } else if(!ignoreLocalPath_ && detector_.guessTorrentFile(uri)) {
       try {
@@ -410,7 +411,7 @@ public:
       } catch(RecoverableException& e) {
         // error occurred while parsing torrent file.
         // We simply ignore it. 
-        LogFactory::getInstance()->error(EX_EXCEPTION_CAUGHT, e);
+        A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
       }
     } 
 #endif // ENABLE_BITTORRENT
@@ -421,12 +422,12 @@ public:
       } catch(RecoverableException& e) {
         // error occurred while parsing metalink file.
         // We simply ignore it.
-        LogFactory::getInstance()->error(EX_EXCEPTION_CAUGHT, e);
+        A2_LOG_ERROR_EX(EX_EXCEPTION_CAUGHT, e);
       }
     }
 #endif // ENABLE_METALINK
     else {
-      LogFactory::getInstance()->error(MSG_UNRECOGNIZED_URI, (uri).c_str());
+      A2_LOG_ERROR(fmt(MSG_UNRECOGNIZED_URI, (uri).c_str()));
     }
   }
 };
diff --git a/src/SimpleLogFormatter.h b/src/fmt.cc
index 5819a500..a4e97330 100644
--- a/src/SimpleLogFormatter.h
+++ b/src/fmt.cc
@@ -32,28 +32,24 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef D_SIMPLE_LOG_FORMATTER_H
-#define D_SIMPLE_LOG_FORMATTER_H
+#include "fmt.h"
 
-#include "LogFormatter.h"
+#include <cstring>
+#include <cstdio>
+#include <cstdlib>
 
 namespace aria2 {
 
-class SimpleLogFormatter:public LogFormatter {
-public:
-  SimpleLogFormatter();
-
-  virtual ~SimpleLogFormatter();
-
-  virtual void writeLog
-  (std::ostream& o, Logger::LEVEL logLevel, const std::string& logLevelLabel,
-   const char* msg, va_list ap);
-
-  virtual void writeStackTrace
-  (std::ostream& o, Logger::LEVEL logLevel, const std::string& logLevelLabel,
-   const Exception& e);
-};
+std::string fmt(const char* fmtTemplate, ...)
+{
+  va_list ap;
+  va_start(ap, fmtTemplate);
+  char buf[1024];
+  if(vsnprintf(buf, sizeof(buf), fmtTemplate, ap) <= 0) {
+    buf[0] = '\0';
+  }
+  va_end(ap);
+  return buf;
+}
 
 } // namespace aria2
-
-#endif // D_SIMPLE_LOG_FORMATTER_H
diff --git a/src/LogFormatter.h b/src/fmt.h
index 7f872298..e94ecb26 100644
--- a/src/LogFormatter.h
+++ b/src/fmt.h
@@ -32,34 +32,18 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef D_LOG_FORMATTER_H
-#define D_LOG_FORMATTER_H
+#ifndef D_FMT_H
+#define D_FMT_H
 
 #include "common.h"
 
-#include <cstdarg>
-#include <iosfwd>
 #include <string>
-
-#include "Logger.h"
+#include <cstdarg>
 
 namespace aria2 {
 
-class Exception;
-
-class LogFormatter {
-public:
-  virtual ~LogFormatter() {}
-
-  virtual void writeLog
-  (std::ostream& o, Logger::LEVEL logLevel, const std::string& logLevelLabel,
-   const char* msg, va_list ap) = 0;
-
-  virtual void writeStackTrace
-  (std::ostream& o, Logger::LEVEL logLevel, const std::string& logLevelLabel,
-   const Exception& ex) = 0;
-};
+std::string fmt(const char* fmt, ...) __attribute__ ((format (printf, 1, 2)));
 
 } // namespace aria2
 
-#endif // D_LOG_FORMATTER_H
+#endif // D_FMT_H
diff --git a/src/main.cc b/src/main.cc
index a5091e03..dfc57b4d 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -68,6 +68,7 @@
 #include "RecoverableException.h"
 #include "SocketCore.h"
 #include "DownloadContext.h"
+#include "fmt.h"
 #ifdef ENABLE_BITTORRENT
 # include "bittorrent_helper.h"
 #endif // ENABLE_BITTORRENT
@@ -187,12 +188,11 @@ downloadresultcode::RESULT main(int argc, char* argv[])
     LogFactory::setConsoleOutput(false);
   }
   downloadresultcode::RESULT exitStatus = downloadresultcode::FINISHED;
-  Logger* logger = LogFactory::getInstance();
-  logger->info("<<--- --- --- ---");
-  logger->info("  --- --- --- ---");
-  logger->info("  --- --- --- --->>");
-  logger->info("%s %s %s", PACKAGE, PACKAGE_VERSION, TARGET);
-  logger->info(MSG_LOGGING_STARTED);
+  A2_LOG_INFO("<<--- --- --- ---");
+  A2_LOG_INFO("  --- --- --- ---");
+  A2_LOG_INFO("  --- --- --- --->>");
+  A2_LOG_INFO(fmt("%s %s %s", PACKAGE, PACKAGE_VERSION, TARGET));
+  A2_LOG_INFO(MSG_LOGGING_STARTED);
 
 #ifdef ENABLE_MESSAGE_DIGEST
   MessageDigestHelper::staticSHA1DigestInit();
diff --git a/src/util.cc b/src/util.cc
index 281bda4f..b42ac20b 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -72,12 +72,14 @@
 #include "FatalException.h"
 #include "FileEntry.h"
 #include "StringFormat.h"
+#include "fmt.h"
 #include "A2STR.h"
 #include "array_fun.h"
 #include "bitfield.h"
 #include "DownloadHandlerConstants.h"
 #include "RequestGroup.h"
 #include "LogFactory.h"
+#include "Logger.h"
 #include "Option.h"
 #ifdef ENABLE_MESSAGE_DIGEST
 # include "MessageDigest.h"
@@ -1451,13 +1453,13 @@ void removeMetalinkContentTypes(const SharedHandle<RequestGroup>& group)
 
 void executeHook(const std::string& command, const std::string& arg)
 {
-  LogFactory::getInstance()->info("Executing user command: %s %s",
-                                  command.c_str(), arg.c_str());
+  A2_LOG_INFO(fmt("Executing user command: %s %s",
+                  command.c_str(),
+                  arg.c_str()));
 #ifndef __MINGW32__
   pid_t cpid = fork();
   if(cpid == -1) {
-    LogFactory::getInstance()->error("fork() failed."
-                                     " Cannot execute user command.");
+    A2_LOG_ERROR("fork() failed. Cannot execute user command.");
   } else if(cpid == 0) {
     execl(command.c_str(), command.c_str(), arg.c_str(),
           reinterpret_cast<char*>(0));
@@ -1488,9 +1490,9 @@ void executeHook(const std::string& command, const std::string& arg)
                            &si,
                            &pi);
 
-  if(!rc)
-    LogFactory::getInstance()->error("CreateProcess() failed."
-                                     " Cannot execute user command.");
+  if(!rc) {
+    A2_LOG_ERROR("CreateProcess() failed. Cannot execute user command.");
+  }
 #endif 
 }