logger: Rework configuration of logger

Most logger configuration that was possible through
kernel application variables have been moved into a
common 'logger' application environment in kernel.

Now all the configuration possible through the logger
API can be done as sys config.

The handler started by kernel has been renamed to 'default'
instead of logger_std_h.

There is a new logger:setup_handlers/1 function that given an
application name can be used to setup handlers in other applications.

1 files changed, 16 insertions, 8 deletions

diff --git a/lib/kernel/src/logger_server.erl b/lib/kernel/src/logger_server.erl
index a7f302ac8f..268fd4f2f3 100644
--- a/lib/kernel/src/logger_server.erl
+++ b/lib/kernel/src/logger_server.erl
@@ -122,8 +122,7 @@ init([]) ->
     logger_config:create(Tid,logger,LoggerConfig),
     SimpleConfig0 = maps:merge(default_config(logger_simple),
                                #{filter_default=>stop,
-                                 filters=>?DEFAULT_HANDLER_FILTERS,
-                                 logger_simple=>#{buffer=>true}}),
+                                 filters=>?DEFAULT_HANDLER_FILTERS}),
     %% If this fails, then the node should crash
     {ok,SimpleConfig} =
         logger_simple:adding_handler(logger_simple,SimpleConfig0),
@@ -139,12 +138,21 @@ handle_call({add_handler,Id,Module,HConfig}, _From, #state{tid=Tid}=State) ->
                 %% inform the handler
                 case call_h(Module,adding_handler,[Id,HConfig],{ok,HConfig}) of
                     {ok,HConfig1} ->
-                        logger_config:create(Tid,Id,Module,HConfig1),
-                        {ok,Config} = do_get_config(Tid,logger),
-                        Handlers = maps:get(handlers,Config,[]),
-                        do_set_config(Tid,logger,
-                                      Config#{handlers=>[Id|Handlers]}),
-                        ok;
+                        %% We know that the call_h would have loaded the module
+                        %% if it existed, so it is safe here to call function_exported
+                        %% to find out if this is a valid handler
+                        case erlang:function_exported(Module, log, 2) of
+                            true ->
+                                logger_config:create(Tid,Id,Module,HConfig1),
+                                {ok,Config} = do_get_config(Tid,logger),
+                                Handlers = maps:get(handlers,Config,[]),
+                                do_set_config(Tid,logger,
+                                              Config#{handlers=>[Id|Handlers]});
+                            false ->
+                                {error,{invalid_handler,
+                                        {function_not_exported,
+                                         {Module,log,2}}}}
+                        end;
                     {error,HReason} ->
                         {error,{handler_not_added,HReason}}
                 end