Add our own error log handler

This handler is logrotate friendly as it does not add any datetime into
the filename and the log file is recreated if moved.

2 files changed, 161 insertions, 1 deletions

diff --git a/src/ldapsp_app.erl b/src/ldapsp_app.erl
index cdc6a22..60cde79 100644
--- a/src/ldapsp_app.erl
+++ b/src/ldapsp_app.erl
@@ -26,7 +26,7 @@
 
 start(_Type, _StartArgs) ->
     LogHandlers = [{webmachine_access_log_handler, ["priv/log"]},
-                   {webmachine_error_log_handler, ["priv/log"]}],
+                   {ldapsp_error_log_handler, ["priv/log"]}],
     application:set_env(webmachine, log_handlers, LogHandlers), 
     % Evil hack so we reprocess the app config
     webmachine:stop(),
diff --git a/src/ldapsp_error_log_handler.erl b/src/ldapsp_error_log_handler.erl
new file mode 100644
index 0000000..f7825ea
--- /dev/null
+++ b/src/ldapsp_error_log_handler.erl
@@ -0,0 +1,160 @@
+%%-----------------------------------------------------------------------
+%% Copyright (c) 2017 Guido Günther
+%%
+%% This file is provided to you under the Apache License,
+%% Version 2.0 (the "License"); you may not use this file
+%% except in compliance with the License.  You may obtain
+%% a copy of the License at
+%%
+%%   http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing,
+%% software distributed under the License is distributed on an
+%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+%% KIND, either express or implied.  See the License for the
+%% specific language governing permissions and limitations
+%% under the License.
+%%
+%% based on error_log_handler.erl
+%% Copyright (c) 2011-2014 Basho Technologies, Inc.  All Rights Reserved.
+%%-----------------------------------------------------------------------
+
+%% @doc Log handler for ldapsp
+
+-module(ldapsp_error_log_handler).
+
+-behaviour(gen_event).
+
+%% gen_event callbacks
+-export([init/1,
+         handle_call/2,
+         handle_event/2,
+         handle_info/2,
+         terminate/2,
+         code_change/3]).
+
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+-endif.
+
+-record(state, {filename, handle}).
+
+-define(FILENAME, "ldapsp_error.log").
+
+%% ===================================================================
+%% gen_event callbacks
+%% ===================================================================
+
+%% @private
+init([BaseDir]) ->
+    {ok,_} = webmachine_log:defer_refresh(?MODULE),
+    FileName = filename:join(BaseDir, ?FILENAME),
+    Handle = log_open(FileName),
+    {ok, #state{filename=FileName, handle=Handle}}.
+
+%% @private
+handle_call({_Label, MRef, get_modules}, State) ->
+    {ok, {MRef, [?MODULE]}, State};
+handle_call({refresh, _Time}, State) ->
+    NewHandle = maybe_reopen(?MODULE,
+			     State#state.filename,
+			     State#state.handle),
+    {ok, ok, State#state{handle=NewHandle}};
+handle_call(_Request, State) ->
+    {ok, ok, State}.
+
+%% @private
+handle_event({log_error, Msg}, State) ->
+    NewHandle = maybe_reopen(?MODULE,
+			     State#state.filename,
+			     State#state.handle),
+    NewState = State#state{handle=NewHandle},
+    FormattedMsg = format_req(error, undefined, undefined, Msg),
+    _ = webmachine_log:log_write(State#state.handle, FormattedMsg),
+    {ok, NewState};
+handle_event({log_error, Code, _Req, _Reason}, State) when Code < 500 ->
+    {ok, State};
+handle_event({log_error, Code, Req, Reason}, State) ->
+    NewHandle = maybe_reopen(?MODULE,
+			     State#state.filename,
+			     State#state.handle),
+    NewState = State#state{handle=NewHandle},
+    Msg = format_req(error, Code, Req, Reason),
+    _ = webmachine_log:log_write(State#state.handle, Msg),
+    {ok, NewState};
+handle_event({log_info, Msg}, State) ->
+    NewHandle = maybe_reopen(?MODULE,
+			     State#state.filename,
+			     State#state.handle),
+    NewState = State#state{handle=NewHandle},
+    FormattedMsg = format_req(info, undefined, undefined, Msg),
+    _ = webmachine_log:log_write(State#state.handle, FormattedMsg),
+    {ok, NewState};
+handle_event(_Event, State) ->
+    {ok, State}.
+
+%% @private
+handle_info(_Info, State) ->
+    {ok, State}.
+
+%% @private
+terminate(_Reason, _State) ->
+    ok.
+
+%% @private
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+
+format_req(Level, Code, Req, Msg) ->
+    Time = webmachine_log:fmtnow(),
+    format_req(Level, Time, Code, Req, Msg).
+
+format_req(info, Time, undefined, _, Msg) ->
+    [Time, " [info] ", Msg];
+format_req(error, Time, undefined, _, Msg) ->
+    [Time, " [error] ", Msg];
+format_req(error, Time, 501, Req, _) ->
+    {Path, _} = Req:path(),
+    {Method, _} = Req:method(),
+    Reason = "Webmachine does not support method ",
+    [Time, " [error] ", Reason, Method, ": path=", Path, $\n];
+format_req(error, Time, 503, Req, _) ->
+    {Path, _} = Req:path(),
+    Reason = "Webmachine cannot fulfill the request at this time",
+    [Time, " [error] ", Reason, ": path=", Path, $\n];
+format_req(error, Time, _Code, Req, Reason) ->
+    {Path, _} = Req:path(),
+    Str = io_lib:format("~p", [Reason]),
+    [Time, " [error] ", "path=", Path, $\x20, Str, $\n].
+
+%% @doc Open a new log file for writing
+-spec log_open(string()) -> file:io_device().
+log_open(LogName) ->
+    error_logger:info_msg("opening log file: ~p~n", [LogName]),
+    ok = filelib:ensure_dir(LogName),
+    {ok, FD} = file:open(LogName, [read, write, raw]),
+    {ok, Location} = file:position(FD, eof),
+    webmachine_log:fix_log(FD, Location),
+    ok = file:truncate(FD),
+    FD.
+
+%% @doc Rotate a log file if the hour it represents
+%% has passed.
+-spec maybe_reopen(atom(), string(), file:io_device()) -> file:io_device().
+maybe_reopen(Mod, FileName, Handle) ->
+    Reopen = not filelib:is_regular(FileName),
+    maybe_reopen(Mod, FileName, Handle, Reopen).
+
+-spec maybe_reopen(atom(), string(), file:io_device(), boolean()) ->
+			  file:io_device().
+maybe_reopen(_Mod, _FileName, Handle, false) ->
+    Handle;
+maybe_reopen(Mod, FileName, Handle, true) ->
+    ok = webmachine_log:log_close(Mod, FileName, Handle),
+    NewHandle = log_open(FileName),
+    NewHandle.