couch_log: make sure that the the log file can be set in the ini

For some reason noone noticed until now, but changing the log file was
only possible in the app.config until now. This change fix this by doing
the following:

- when couch_log starts it check if the log file handler has already
  been started using the app.config. If not it start a new handler
- when the filename change after a config update using the API, the old
  file handler is shutdown and a new one is started with the new config.

2 files changed, 77 insertions, 11 deletions

diff --git a/apps/couch/src/couch_log.erl b/apps/couch/src/couch_log.erl
index 82158f6ed..787f25a11 100644
--- a/apps/couch/src/couch_log.erl
+++ b/apps/couch/src/couch_log.erl
@@ -144,6 +144,9 @@ init([]) ->
     Sasl = couch_config:get("log", "include_sasl", "true") =:= "true",
     LevelByModule = couch_config:get("log_level_by_module"),
 
+    %% maybe start the log file backend
+    maybe_start_logfile_backend(Filename, ALevel),
+
     %% initialise the ets table if needed
     case ets:info(?MODULE) of
         undefined -> ets:new(?MODULE, [named_table]);
@@ -172,7 +175,7 @@ handle_call({set_level_integer, Module, NewLevel}, _From, State) ->
     ets:insert(?MODULE, {Module, NewLevel}),
     {ok, ok, State#state{level = NewLevel}}.
 
-handle_cast(config_update, State) ->
+handle_cast(config_update, #state{log_file=OldFilename}=State) ->
     Filename = log_file(),
     ALevel = list_to_atom(couch_config:get("log", "level", "info")),
     Level = level_integer(ALevel),
@@ -180,6 +183,12 @@ handle_cast(config_update, State) ->
     %% set default module
     ets:insert(?MODULE, {level, Level}),
 
+    %% should we restart the file backend with a new config?
+    if OldFilename =/= Filename ->
+            restart_logfile_backend(OldFilename, Filename, ALevel);
+        true -> ok
+    end,
+
     %% set log level
     set_loglevel(Filename, ALevel),
 
@@ -246,6 +255,50 @@ read(Bytes, Offset) ->
     ok = file:close(Fd),
     Chunk.
 
+
+maybe_start_logfile_backend(Filename, Level) ->
+    Started = case application:get_env(lager, handlers) of
+        undefined -> false;
+        {ok, Handlers} ->
+            LogFiles = lists:foldl(fun
+                    ({lager_file_backend, Config}, Acc) ->
+                        [hfile(Config) | Acc];
+                    (_, Acc) ->
+                        Acc
+                end, [], Handlers),
+            lists:member(Filename, LogFiles)
+    end,
+
+    case Started of
+        true -> ok;
+        false ->
+            Config = [{file, Filename},
+                      {level, Level},
+                      {formatter, lager_default_formatter},
+                      {formatter_config,
+                       ["[", time, "] [", pid, "] [", severity, "] ",
+                        message, "\n"]}],
+            HandlerId = {lager_file_backend, Filename},
+            {ok, _} = supervisor:start_child(lager_handler_watcher_sup,
+                                             [lager_event, HandlerId, Config])
+    end.
+
+
+restart_logfile_backend(OldFilename, Filename, Level) ->
+    ok = gen_event:delete_handler(lager_event, {lager_file_backend,
+                                                OldFilename}, []),
+
+    %% restart a new handler
+    Config = [{file, Filename},
+              {level, Level},
+              {formatter, lager_default_formatter},
+              {formatter_config,
+               ["[", time, "] [", pid, "] [", severity, "] ", message, "\n"]}],
+    HandlerId = {lager_file_backend, Filename},
+    {ok, _} = supervisor:start_child(lager_handler_watcher_sup,
+                                     [lager_event, HandlerId, Config]),
+    ok.
+
 set_loglevel(Filename, ALevel) ->
     %% set default log level
     lager:set_loglevel(lager_console_backend, ALevel),
@@ -260,10 +313,30 @@ set_loglevel(Filename, ALevel) ->
                 end, Handlers)
     end.
 
-
 log_file() ->
     DefaultLogFile = case application:get_env(couch, log_file) of
         undefined -> "couchdb.log";
         FName -> FName
     end,
     couch_config:get("log", "file", DefaultLogFile).
+
+hfile({FileName, LogLevel}) when is_list(FileName), is_atom(LogLevel) ->
+    %% backwards compatability hack
+    FileName;
+hfile({FileName, LogLevel, _Size, _Date, _Count})
+        when is_list(FileName), is_atom(LogLevel) ->
+    %% backwards compatability hack
+    FileName;
+hfile([{FileName, LogLevel, _Size, _Date, _Count}, {Formatter, _FormatterConfig}])
+    when is_list(FileName), is_atom(LogLevel), is_atom(Formatter) ->
+    %% backwards compatability hack
+    FileName;
+hfile([LogFile,{Formatter}]) ->
+    %% backwards compatability hack
+    hfile([LogFile,{Formatter,[]}]);
+hfile([{FileName, LogLevel}, {Formatter, _FormatterConfig}])
+    when is_list(FileName), is_atom(LogLevel), is_atom(Formatter) ->
+    %% backwards compatability hack
+   FileName;
+hfile(LogFileConfig) when is_list(LogFileConfig) ->
+    proplists:get_value(file, LogFileConfig).
diff --git a/etc/couchdb/app.config b/etc/couchdb/app.config
index b6d247c7a..1db33ecad 100644
--- a/etc/couchdb/app.config
+++ b/etc/couchdb/app.config
@@ -8,7 +8,7 @@
                 "{{platform_etc_dir}}/couch.ini",
                 "{{platform_etc_dir}}/local.ini"
                 ]},
-        {log_file, "{{platform_log_dir}}/couchdb.log"}
+        {log_file, "{{platform_log_dir}}/couch.log"}
     ]},
 
 
@@ -16,14 +16,7 @@
           {lager_console_backend, [info,
                                    {lager_default_formatter,
                                           ["[", pid, "] [", severity, "] ",
-                                           message, "\n"]}]},
-
-          {lager_file_backend, [{file, "{{platform_log_dir}}/couchdb.log"},
-                                 {level, info},
-                                 {formatter, lager_default_formatter},
-                                 {formatter_config,
-                                  ["[", time, "] [", pid, "] [", severity, "] ",
-                                   message, "\n"]}]}
+                                           message, "\n"]}]}
                     ]}]},
 
  %% os_mon config