Add simple size based log rotation

src/lager.app.src

@@ -16,8 +16,8 @@
             {handlers, [
                 {lager_console_backend, info},
                 {lager_file_backend, [
-                    {"log/error.log", error},
-                    {"log/console.log", info}
+                    {"log/error.log", error, 10485760, "", 5},
+                    {"log/console.log", info, 10485760, "", 5}
                 ]}
             ]},
             %% Whether to write a crash log, and where. Undefined means no crash logger.

src/lager_app.erl

@@ -34,7 +34,8 @@ start(_StartType, _StartArgs) ->
     Handlers = case application:get_env(lager, handlers) of
         undefined ->
             [{lager_console_backend, info},
-                {lager_file_backend, [{"log/error.log", error}, {"log/console.log", info}]}];
+                {lager_file_backend, [{"log/error.log", error, 10485760, "", 5},
+                        {"log/console.log", info, 10485760, "", 5}]}];
         {ok, Val} ->
             Val
     end,

src/lager_crash_log.erl

@@ -51,7 +51,7 @@ start(Filename, MaxBytes) ->
 %% @private
 init([Filename, MaxBytes]) ->
     case lager_util:open_logfile(Filename, false) of
-        {ok, {FD, Inode}} ->
+        {ok, {FD, Inode, _}} ->
             {ok, #state{name=Filename, fd=FD, inode=Inode, fmtmaxbytes=MaxBytes}};
         Error ->
             Error
@@ -78,7 +78,7 @@ handle_cast({log, Event}, #state{name=Name, fd=FD, inode=Inode, flap=Flap, fmtma
             {noreply, State};
         true ->
             case lager_util:ensure_logfile(Name, FD, Inode, false) of
-                {ok, {NewFD, NewInode}} ->
+                {ok, {NewFD, NewInode, _Size}} ->
                     {Date, TS} = lager_util:format_time(lager_stdlib:maybe_utc(erlang:localtime())),
                     Time = [Date, " ", TS," =", ReportStr, "====\n"],
                     NodeSuffix = other_node_suffix(Pid),

src/lager_file_backend.erl

@@ -42,7 +42,10 @@
         level :: integer(),
         fd :: file:io_device(),
         inode :: integer(),
-        flap=false :: boolean()
+        flap=false :: boolean(),
+        size = 0 :: integer(),
+        date,
+        count = 10
     }).
 
 %% @private
@@ -50,15 +53,17 @@
 init(LogFiles) ->
     Files = [begin
                 case lager_util:open_logfile(Name, true) of
-                    {ok, {FD, Inode}} ->
-                        #file{name=Name, level=lager_util:level_to_num(Level), fd=FD, inode=Inode};
+                    {ok, {FD, Inode, _}} ->
+                        #file{name=Name, level=lager_util:level_to_num(Level), fd=FD,
+                            inode=Inode, size=Size, date=Date, count=Count};
                     {error, Reason} ->
                         ?INT_LOG(error, "Failed to open log file ~s with error ~s",
                             [Name, file:format_error(Reason)]),
-                        #file{name=Name, level=lager_util:level_to_num(Level), flap=true}
+                        #file{name=Name, level=lager_util:level_to_num(Level),
+                            flap=true, size=Size, date=Date, count=Count}
                 end
         end ||
-        {Name, Level} <- LogFiles],
+        {Name, Level, Size, Date, Count} <- validate_logfiles(LogFiles)],
     {ok, #state{files=Files}}.
 
 %% @private
@@ -114,9 +119,13 @@ terminate(_Reason, State) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
-write(#file{name=Name, fd=FD, inode=Inode, flap=Flap} = File, Level, Msg) ->
+write(#file{name=Name, fd=FD, inode=Inode, flap=Flap, size=RotSize,
+        count=Count} = File, Level, Msg) ->
     case lager_util:ensure_logfile(Name, FD, Inode, true) of
-        {ok, {NewFD, NewInode}} ->
+        {ok, {_, _, Size}} when RotSize /= 0, Size > RotSize ->
+            lager_util:rotate_logfile(Name, Count),
+            write(File, Level, Msg);
+        {ok, {NewFD, NewInode, _}} ->
             file:write(NewFD, Msg),
             case Level of
                 _ when Level =< ?ERROR ->
@@ -144,6 +153,36 @@ write(#file{name=Name, fd=FD, inode=Inode, flap=Flap} = File, Level, Msg) ->
             end
     end.
 
+validate_logfiles([]) ->
+    [];
+validate_logfiles([{Name, Level, Size, Date, Count}|T]) ->
+    case lists:member(Level, ?LEVELS) of
+        true ->
+            case (is_integer(Size) andalso Size >= 0) of
+                true ->
+                    case (is_integer(Count) andalso Count >= 0) of
+                        true ->
+                            [{Name, Level, Size, Date,
+                                    Count}|validate_logfiles(T)];
+                        _ ->
+                            ?INT_LOG(error, "Invalid rotation count of ~p for ~s.",
+                                [Name, Count]),
+                            validate_logfiles(T)
+                    end;
+                _ ->
+                    ?INT_LOG(error, "Invalid rotation size of ~p for ~s.",
+                        [Name, Size]),
+                    validate_logfiles(T)
+            end;
+        _ ->
+            ?INT_LOG(error, "Invalid log level of ~p for ~s.",
+                [Name, Level]),
+            validate_logfiles(T)
+    end;
+validate_logfiles([H|T]) ->
+    ?INT_LOG(error, "Invalid logfile config ~p.", [H]),
+    validate_logfiles(T).
+
 -ifdef(TEST).
 
 get_loglevel_test() ->
@@ -160,7 +199,7 @@ get_loglevel_test() ->
     ?assertEqual(Level2, lager_util:level_to_num(warning)).
 
 rotation_test() ->
-    {ok, {FD, Inode}} = lager_util:open_logfile("test.log", true),
+    {ok, {FD, Inode, _}} = lager_util:open_logfile("test.log", true),
     ?assertMatch(#file{name="test.log", level=?DEBUG, fd=FD, inode=Inode},
         write(#file{name="test.log", level=?DEBUG, fd=FD, inode=Inode}, 0, "hello world")),
     file:delete("test.log"),

src/lager_handler_watcher.erl

@@ -80,9 +80,10 @@ install_handler(Event, Module, Config) ->
         ok ->
             lager:log(debug, self(), "Lager installed handler ~p into ~p", [Module, Event]),
             ok;
-        _ ->
+        Error ->
             %% try to reinstall it later
-            lager:log(error, self(), "Lager failed to install handler ~p into ~p, retrying later", [Module, Event]),
+            lager:log(error, self(), "Lager failed to install handler ~p into"
+               " ~p, retrying later : ~p", [Module, Event, Error]),
             erlang:send_after(5000, self(), reinstall_handler)
     end.
 

src/lager_util.erl

@@ -19,7 +19,7 @@
 -include_lib("kernel/include/file.hrl").
 
 -export([levels/0, level_to_num/1, num_to_level/1, open_logfile/2,
-        ensure_logfile/4, format_time/0, format_time/1, localtime_ms/0, maybe_utc/1]).
+        ensure_logfile/4, rotate_logfile/2, format_time/0, format_time/1, localtime_ms/0, maybe_utc/1]).
 
 levels() ->
     [debug, info, notice, warning, error, critical, alert, emergency].
@@ -54,7 +54,7 @@ open_logfile(Name, Buffer) ->
                     case file:read_file_info(Name) of
                         {ok, FInfo} ->
                             Inode = FInfo#file_info.inode,
-                            {ok, {FD, Inode}};
+                            {ok, {FD, Inode, FInfo#file_info.size}};
                         X -> X
                     end;
                 Y -> Y
@@ -68,16 +68,16 @@ ensure_logfile(Name, FD, Inode, Buffer) ->
             Inode2 = FInfo#file_info.inode,
             case Inode == Inode2 of
                 true ->
-                    {ok, {FD, Inode}};
+                    {ok, {FD, Inode, FInfo#file_info.size}};
                 false ->
                     %% delayed write can cause file:close not to do a close
                     file:close(FD),
                     file:close(FD),
                     case open_logfile(Name, Buffer) of
-                        {ok, {FD2, Inode3}} ->
+                        {ok, {FD2, Inode3, Size}} ->
                             %% inode changed, file was probably moved and
                             %% recreated
-                            {ok, {FD2, Inode3}};
+                            {ok, {FD2, Inode3, Size}};
                         Error ->
                             Error
                     end
@@ -87,9 +87,9 @@ ensure_logfile(Name, FD, Inode, Buffer) ->
             file:close(FD),
             file:close(FD),
             case open_logfile(Name, Buffer) of
-                {ok, {FD2, Inode3}} ->
+                {ok, {FD2, Inode3, Size}} ->
                     %% file was removed
-                    {ok, {FD2, Inode3}};
+                    {ok, {FD2, Inode3, Size}};
                 Error ->
                     Error
             end
@@ -109,6 +109,16 @@ maybe_utc({Date, {H, M, S, Ms}}) ->
             {Date1, {H1, M1, S1, Ms}}
     end.
 
+rotate_logfile(File, 0) ->
+    file:delete(File);
+rotate_logfile(File, 1) ->
+    file:rename(File, File++".0"),
+    rotate_logfile(File, 0);
+rotate_logfile(File, Count) ->
+    file:rename(File ++ "." ++ integer_to_list(Count - 2), File ++ "." ++
+        integer_to_list(Count - 1)),
+    rotate_logfile(File, Count - 1).
+
 format_time() ->
     format_time(maybe_utc(localtime_ms())).