Misunderstood the inbound Module term. Should probably have specs and/or a different name. Actually represents the unique ID we want, e.g. {lager_file_handler, "foo.log"}

src/lager_app.erl

@@ -87,8 +87,7 @@ start_handlers(Sink, {ok, Handlers}) ->
 start_handler(Sink, Module, Config) ->
     {ok, Watcher} = supervisor:start_child(lager_handler_watcher_sup,
                                            [Sink, Module, Config]),
-    {BackendId, _Config} = maybe_make_handler_id(Module, Config),
-    {BackendId, Watcher, Sink}.
+    {Module, Watcher, Sink}.
 
 interpret_hwm(undefined) ->
     undefined;