Make the size of messages in the crash log configurable

src/lager.app.src

@@ -18,6 +18,8 @@
                 {"log/console.log", info}]}]},
             %% Whether to write a crash log, and where. Undefined means no crash logger.
             {crash_log, "log/crash.log"},
+            %% Maximum size in bytes of events in the crash log - defaults to 4096
+            {crash_log_size, 4096},
             %% Whether to redirect error_logger messages into lager - defaults to true
             {error_logger_redirect, true}
         ]}

src/lager_crash_log.erl

@@ -30,28 +30,29 @@
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
         code_change/3]).
 
--export([start_link/1, start/1]).
+-export([start_link/2, start/2]).
 
 -record(state, {
         name,
         fd,
         inode,
+        fmtmaxbytes,
         flap=false
     }).
 
 %% @private
-start_link(Filename) ->
-    gen_server:start_link({local, ?MODULE}, ?MODULE, [Filename], []).
+start_link(Filename, MaxBytes) ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [Filename, MaxBytes], []).
 
 %% @private
-start(Filename) ->
-    gen_server:start({local, ?MODULE}, ?MODULE, [Filename], []).
+start(Filename, MaxBytes) ->
+    gen_server:start({local, ?MODULE}, ?MODULE, [Filename, MaxBytes], []).
 
 %% @private
-init([Filename]) ->
+init([Filename, MaxBytes]) ->
     case lager_util:open_logfile(Filename, false) of
         {ok, {FD, Inode}} ->
-            {ok, #state{name=Filename, fd=FD, inode=Inode}};
+            {ok, #state{name=Filename, fd=FD, inode=Inode, fmtmaxbytes=MaxBytes}};
         Error ->
             Error
     end.
@@ -61,9 +62,7 @@ handle_call(_Call, _From, State) ->
     {reply, ok, State}.
 
 %% @private
-handle_cast({log, Event}, #state{name=Name, fd=FD, inode=Inode, flap=Flap} = State) ->
-    %% TODO these should probably be configurable and have saner defaults
-    FmtMaxBytes = 1024,
+handle_cast({log, Event}, #state{name=Name, fd=FD, inode=Inode, flap=Flap, fmtmaxbytes=FmtMaxBytes} = State) ->
     TermMaxSize = 500,
     %% borrowed from riak_err
     {ReportStr, Pid, MsgStr, _ErrorP} = case Event of

src/lager_sup.erl

@@ -41,7 +41,11 @@ init([]) ->
     %% check if the crash log is enabled
     Crash = case application:get_env(lager, crash_log) of
         {ok, File} ->
-            [{lager_crash_log, {lager_crash_log, start_link, [File]},
+            MaxBytes = case application:get_env(lager, crash_log_size) of
+                {ok, Val} -> Val;
+                _ -> 4096
+            end,
+            [{lager_crash_log, {lager_crash_log, start_link, [File, MaxBytes]},
                     permanent, 5000, worker, [lager_crash_log]}];
         _ ->
             []