--- Revision None
+++ Revision 353336333637
@@ -0,0 +1,116 @@
+diff --git a/src/couchdb/couch_log.erl b/src/couchdb/couch_log.erl
+index 2676689..03e2fa7 100644
+--- a/src/couchdb/couch_log.erl
++++ b/src/couchdb/couch_log.erl
+@@ -27,10 +27,12 @@
+ -define(LEVEL_INFO, 2).
+ -define(LEVEL_DEBUG, 1).
+ 
++-define(MAX_BUFFER_LEN, 64 * 1024).
++
+ -record(state, {
+-    fd,
+     level,
+-    sasl
++    sasl,
++    writer
+ }).
+ 
+ debug(Format, Args) ->
+@@ -81,17 +83,21 @@ init([]) ->
+     Sasl = couch_config:get("log", "include_sasl", "true") =:= "true",
+ 
+     case ets:info(?MODULE) of
+-    undefined -> ets:new(?MODULE, [named_table]);
++    undefined -> ets:new(?MODULE, [named_table, {read_concurrency, true}]);
+     _ -> ok
+     end,
+     ets:insert(?MODULE, {level, Level}),
+ 
+-    case file:open(Filename, [append]) of
+-    {ok, Fd} ->
+-        {ok, #state{fd = Fd, level = Level, sasl = Sasl}};
+-    {error, eacces} ->
++    process_flag(trap_exit, true),
++    Parent = self(),
++    Writer = spawn_link(fun() -> writer(Parent, Filename) end),
++
++    receive
++    {Writer, ok} ->
++        {ok, #state{writer = Writer, level = Level, sasl = Sasl}};
++    {Writer, {error, eacces}} ->
+         {stop, {file_permission_error, Filename}};
+-    Error ->
++    {Writer, Error} ->
+         {stop, Error}
+     end.
+ 
+@@ -143,18 +149,21 @@ handle_call({set_level_integer, NewLevel}, State) ->
+     ets:insert(?MODULE, {level, NewLevel}),
+     {ok, ok, State#state{level = NewLevel}}.
+ 
++handle_info({'EXIT', Pid, Reason}, #state{writer = Pid}) ->
++    io:format("[error] log writer died: ~p~n", [Reason]),
++    exit({log_writer_died, Reason});
+ handle_info(_Info, State) ->
+     {ok, State}.
+ 
+ code_change(_OldVsn, State, _Extra) ->
+     {ok, State}.
+ 
+-terminate(_Arg, #state{fd = Fd}) ->
+-    file:close(Fd).
++terminate(_Arg, #state{writer = Writer}) ->
++    Writer ! stop,
++    receive {'EXIT', Writer, _} -> ok end.
+ 
+-log(#state{fd = Fd}, ConsoleMsg, FileMsg) ->
+-    ok = io:put_chars(ConsoleMsg),
+-    ok = io:put_chars(Fd, FileMsg).
++log(#state{writer = Writer}, ConsoleMsg, FileMsg) ->
++    Writer ! {log, FileMsg, ConsoleMsg}.
+ 
+ get_log_messages(Pid, Level, Format, Args) ->
+     ConsoleMsg = unicode:characters_to_binary(io_lib:format(
+@@ -175,3 +184,41 @@ read(Bytes, Offset) ->
+     {ok, Chunk} = file:pread(Fd, Start, LogFileSize),
+     ok = file:close(Fd),
+     Chunk.
++
++
++writer(Parent, Filename) ->
++    case file:open(Filename, [append, raw, binary]) of
++    {ok, Fd} ->
++        Parent ! {self(), ok},
++        writer_loop(Fd);
++    Error ->
++        Parent ! {self(), Error}
++    end.
++
++writer_loop(Fd) ->
++    receive
++    {log, FileMsg, ConsoleMsg} ->
++        ok = io:put_chars(ConsoleMsg),
++        ok = file:write(Fd, FileMsg),
++        writer_loop(Fd);
++        % writer_loop_batch(Fd, [FileMsg], [ConsoleMsg], byte_size(FileMsg));
++    stop ->
++        ok = file:close(Fd)
++    end.
++
++writer_loop_batch(Fd, AccFile, AccConsole, Len) when Len >= ?MAX_BUFFER_LEN ->
++    ok = io:put_chars(lists:reverse(AccConsole)),
++    ok = file:write(Fd, lists:reverse(AccFile)),
++    writer_loop(Fd);
++
++writer_loop_batch(Fd, AccFile, AccConsole, Len) ->
++    receive
++    {log, FileMsg, ConsoleMsg} ->
++        writer_loop_batch(
++            Fd, [FileMsg | AccFile], [ConsoleMsg | AccConsole],
++            Len + byte_size(FileMsg))
++    after 0 ->
++        ok = io:put_chars(lists:reverse(AccConsole)),
++        ok = file:write(Fd, lists:reverse(AccFile)),
++        writer_loop(Fd)
++    end.