Rework using safe_format() from one of Andrew's branches

src/lager.erl

@@ -55,7 +55,7 @@ log(Level, Module, Function, Line, Pid, Time, Message) ->
     Timestamp = lager_util:format_time(Time),
     Msg = [["[", atom_to_list(Level), "] "],
            io_lib:format("~p@~p:~p:~p ", [Pid, Module, Function, Line]),
-           string_reduce(Message)],
+           format_string_chop("~s", [Message], 4096)],
     safe_notify(lager_util:level_to_num(Level), Timestamp, Msg).
 
 %% @private
@@ -64,8 +64,8 @@ log(Level, Module, Function, Line, Pid, Time, Message) ->
 log(Level, Module, Function, Line, Pid, Time, Format, Args) ->
     Timestamp = lager_util:format_time(Time),
     Msg = [["[", atom_to_list(Level), "] "],
-        io_lib:format("~p@~p:~p:~p ", [Pid, Module, Function, Line]),
-        string_reduce(lager_trunc_io:format(Format, Args, 4096))],
+           io_lib:format("~p@~p:~p:~p ", [Pid, Module, Function, Line]),
+           format_string_chop(Format, Args, 4096)],
     safe_notify(lager_util:level_to_num(Level), Timestamp, Msg).
 
 %% @doc Manually log a message into lager without using the parse transform.
@@ -73,7 +73,7 @@ log(Level, Module, Function, Line, Pid, Time, Format, Args) ->
 log(Level, Pid, Message) ->
     Timestamp = lager_util:format_time(),
     Msg = [["[", atom_to_list(Level), "] "], io_lib:format("~p ", [Pid]),
-        string_reduce(Message)],
+           format_string_chop("~s", [Message], 4096)],
     safe_notify(lager_util:level_to_num(Level), Timestamp, Msg).
 
 %% @doc Manually log a message into lager without using the parse transform.
@@ -81,7 +81,7 @@ log(Level, Pid, Message) ->
 log(Level, Pid, Format, Args) ->
     Timestamp = lager_util:format_time(),
     Msg = [["[", atom_to_list(Level), "] "], io_lib:format("~p ", [Pid]),
-        string_reduce(lager_trunc_io:format(Format, Args, 4096))],
+           format_string_chop(Format, Args, 4096)],
     safe_notify(lager_util:level_to_num(Level), Timestamp, Msg).
 
 %% @doc Set the loglevel for a particular backend.
@@ -118,7 +118,7 @@ posix_error(Error) when is_atom(Error) ->
         Message -> Message
     end;
 posix_error(Error) ->
-    lists:flatten(lager_trunc_io:format("~p", [Error], 4096)).
+    format_string_chop("~p", [Error], 4096).
 
 %% @private
 get_loglevels() ->
@@ -140,6 +140,18 @@ safe_notify(Level, Timestamp, Msg) ->
             gen_event:sync_notify(Pid, {log, Level, Timestamp, Msg})
     end.
 
+%% @doc Print the format string `Fmt' with `Args' safely with a size
+%% limit of `Limit'. If the format string is invalid, or not enough
+%% arguments are supplied 'FORMAT ERROR' is printed with the offending
+%% arguments. The caller is NOT crashed.
+
+safe_format(Fmt, Args, Limit) ->
+    try lager_trunc_io:format(Fmt, Args, Limit) of
+        Result -> Result
+    catch
+        _:_ -> lager_trunc_io:format("FORMAT ERROR: ~p ~p", [Fmt, Args], Limit)
+    end.
+
 %% @private
-string_reduce(IOdata) ->
-    re:replace(IOdata, "\n$", "", [{return, list}]).
+format_string_chop(Fmt, Args, Limit) ->
+    re:replace(safe_format(Fmt, Args, Limit), "\n$", "", [{return, list}]).