Introduce undocumented option logger

This commit reworks the logging that Cowboy does via
error_logger to make the module that will do the actual
logging configurable.

The logger module interface must be the same as logger
and lager: a separate function per log level with the
same log levels they support.

The default behavior remains to call error_logger,
although some messages were downgraded to warnings
instead of errors. Since error_logger only supports
three different log levels, some messages may get
downgraded/upgraded depending on what the original
log level was to make them compatible with error_logger.

The {log, Level, Format, Args} command was also
added to stream handlers. Stream handlers should
use this command to log messages because it allows
writing a stream handler to intercept some of those
messages and extract information or block them as
necessary.

The logger option only applies to Cowboy itself,
not to the messages Ranch logs, so more work remains
to be done in that area.

1 files changed, 39 insertions, 32 deletions

diff --git a/src/cowboy_http2.erl b/src/cowboy_http2.erl
index 70a5e46..c2686aa 100644
--- a/src/cowboy_http2.erl
+++ b/src/cowboy_http2.erl
@@ -311,7 +311,7 @@ loop(State=#state{parent=Parent, socket=Socket, transport=Transport,
 			cowboy_children:handle_supervisor_call(Call, From, Children, ?MODULE),
 			loop(State, Buffer);
 		Msg ->
-			error_logger:error_msg("Received stray message ~p.", [Msg]),
+			cowboy:log(warning, "Received stray message ~p.", [Msg], Opts),
 			loop(State, Buffer)
 	after InactivityTimeout ->
 		terminate(State, {internal_error, timeout, 'No message or data received before timeout.'})
@@ -567,14 +567,15 @@ data_frame(State, Stream0=#stream{id=StreamID, remote_window=StreamWindow,
 %% We ignore DATA frames for streams that are flushing out data.
 data_frame(State, Stream=#stream{state=flush}, _, _) ->
 	after_commands(State, Stream);
-data_frame(State, Stream=#stream{id=StreamID, state=StreamState0}, IsFin, Data) ->
+data_frame(State=#state{opts=Opts}, Stream=#stream{id=StreamID, state=StreamState0},
+		IsFin, Data) ->
 	try cowboy_stream:data(StreamID, IsFin, Data, StreamState0) of
 		{Commands, StreamState} ->
 			commands(State, Stream#stream{state=StreamState}, Commands)
 	catch Class:Exception ->
-		cowboy_stream:report_error(data,
+		cowboy:log(cowboy_stream:make_error_log(data,
 			[StreamID, IsFin, Data, StreamState0],
-			Class, Exception, erlang:get_stacktrace()),
+			Class, Exception, erlang:get_stacktrace()), Opts),
 		stream_reset(State, StreamID, {internal_error, {Class, Exception},
 			'Unhandled exception in cowboy_stream:data/4.'})
 	end.
@@ -614,7 +615,7 @@ continuation_frame(State, _) ->
 	terminate(State, {connection_error, protocol_error,
 		'An invalid frame was received in the middle of a header block. (RFC7540 6.2)'}).
 
-down(State=#state{children=Children0}, Pid, Msg) ->
+down(State=#state{opts=Opts, children=Children0}, Pid, Msg) ->
 	case cowboy_children:down(Children0, Pid) of
 		%% The stream was terminated already.
 		{ok, undefined, Children} ->
@@ -624,23 +625,25 @@ down(State=#state{children=Children0}, Pid, Msg) ->
 			info(State#state{children=Children}, StreamID, Msg);
 		%% The process was unknown.
 		error ->
-			error_logger:error_msg("Received EXIT signal ~p for unknown process ~p.~n", [Msg, Pid]),
+			cowboy:log(warning, "Received EXIT signal ~p for unknown process ~p.~n",
+				[Msg, Pid], Opts),
 			State
 	end.
 
-info(State=#state{client_streamid=LastStreamID, streams=Streams}, StreamID, Msg) ->
+info(State=#state{opts=Opts, client_streamid=LastStreamID, streams=Streams}, StreamID, Msg) ->
 	case lists:keyfind(StreamID, #stream.id, Streams) of
 		#stream{state=flush} ->
-			error_logger:error_msg("Received message ~p for terminated stream ~p.", [Msg, StreamID]),
+			cowboy:log(warning, "Received message ~p for terminated stream ~p.",
+				[Msg, StreamID], Opts),
 			State;
 		Stream = #stream{state=StreamState0} ->
 			try cowboy_stream:info(StreamID, Msg, StreamState0) of
 				{Commands, StreamState} ->
 					commands(State, Stream#stream{state=StreamState}, Commands)
 			catch Class:Exception ->
-				cowboy_stream:report_error(info,
+				cowboy:log(cowboy_stream:make_error_log(info,
 					[StreamID, Msg, StreamState0],
-					Class, Exception, erlang:get_stacktrace()),
+					Class, Exception, erlang:get_stacktrace()), Opts),
 				stream_reset(State, StreamID, {internal_error, {Class, Exception},
 					'Unhandled exception in cowboy_stream:info/3.'})
 			end;
@@ -650,8 +653,8 @@ info(State=#state{client_streamid=LastStreamID, streams=Streams}, StreamID, Msg)
 			%% around. In these cases we do not want to log anything.
 			State;
 		false ->
-			error_logger:error_msg("Received message ~p for unknown stream ~p.",
-				[Msg, StreamID]),
+			cowboy:log(warning, "Received message ~p for unknown stream ~p.",
+				[Msg, StreamID], Opts),
 			State
 	end.
 
@@ -782,7 +785,11 @@ commands(State0, #stream{id=StreamID}, [{switch_protocol, Headers, _Mod, _ModSta
 commands(State, Stream=#stream{id=StreamID}, [stop|_Tail]) ->
 	%% @todo Do we want to run the commands after a stop?
 	%% @todo Do we even allow commands after?
-	stream_terminate(after_commands(State, Stream), StreamID, normal).
+	stream_terminate(after_commands(State, Stream), StreamID, normal);
+%% Log event.
+commands(State=#state{opts=Opts}, StreamID, [Log={log, _, _, _}|Tail]) ->
+	cowboy:log(Log, Opts),
+	commands(State, StreamID, Tail).
 
 after_commands(State=#state{streams=Streams0}, Stream=#stream{id=StreamID}) ->
 	Streams = lists:keystore(StreamID, #stream.id, Streams0, Stream),
@@ -952,12 +959,12 @@ terminate(undefined, Reason) ->
 terminate(#state{socket=Socket, transport=Transport, parse_state={preface, _, _}}, Reason) ->
 	Transport:close(Socket),
 	exit({shutdown, Reason});
-terminate(#state{socket=Socket, transport=Transport, client_streamid=LastStreamID,
+terminate(State=#state{socket=Socket, transport=Transport, client_streamid=LastStreamID,
 		streams=Streams, children=Children}, Reason) ->
 	%% @todo We might want to optionally send the Reason value
 	%% as debug data in the GOAWAY frame here. Perhaps more.
 	Transport:send(Socket, cow_http2:goaway(LastStreamID, terminate_reason(Reason), <<>>)),
-	terminate_all_streams(Streams, Reason),
+	terminate_all_streams(State, Streams, Reason),
 	cowboy_children:terminate(Children),
 	Transport:close(Socket),
 	exit({shutdown, Reason}).
@@ -967,14 +974,14 @@ terminate_reason({stop, _, _}) -> no_error;
 terminate_reason({socket_error, _, _}) -> internal_error;
 terminate_reason({internal_error, _, _}) -> internal_error.
 
-terminate_all_streams([], _) ->
+terminate_all_streams(_, [], _) ->
 	ok;
 %% This stream was already terminated and is now just flushing the data out. Skip it.
-terminate_all_streams([#stream{state=flush}|Tail], Reason) ->
-	terminate_all_streams(Tail, Reason);
-terminate_all_streams([#stream{id=StreamID, state=StreamState}|Tail], Reason) ->
-	stream_call_terminate(StreamID, Reason, StreamState),
-	terminate_all_streams(Tail, Reason).
+terminate_all_streams(State, [#stream{state=flush}|Tail], Reason) ->
+	terminate_all_streams(State, Tail, Reason);
+terminate_all_streams(State, [#stream{id=StreamID, state=StreamState}|Tail], Reason) ->
+	stream_call_terminate(StreamID, Reason, StreamState, State),
+	terminate_all_streams(State, Tail, Reason).
 
 %% Stream functions.
 
@@ -1214,9 +1221,9 @@ stream_early_error(State0=#state{ref=Ref, opts=Opts, peer=Peer,
 					State#state{streams=[Stream|Streams]}
 			end
 	catch Class:Exception ->
-		cowboy_stream:report_error(early_error,
+		cowboy:log(cowboy_stream:make_error_log(early_error,
 			[StreamID, Reason, PartialReq, Resp, Opts],
-			Class, Exception, erlang:get_stacktrace()),
+			Class, Exception, erlang:get_stacktrace()), Opts),
 		%% We still need to send an error response, so send what we initially
 		%% wanted to send. It's better than nothing.
 		send_headers(State0, Stream0, StatusCode0, RespHeaders0, fin)
@@ -1237,9 +1244,9 @@ stream_handler_init(State=#state{opts=Opts,
 					te=maps:get(<<"te">>, Headers, undefined)},
 				Commands)
 	catch Class:Exception ->
-		cowboy_stream:report_error(init,
+		cowboy:log(cowboy_stream:make_error_log(init,
 			[StreamID, Req, Opts],
-			Class, Exception, erlang:get_stacktrace()),
+			Class, Exception, erlang:get_stacktrace()), Opts),
 		stream_reset(State, StreamID, {internal_error, {Class, Exception},
 			'Unhandled exception in cowboy_stream:init/3.'})
 	end.
@@ -1308,7 +1315,7 @@ stream_terminate(State0=#state{streams=Streams0, children=Children0}, StreamID,
 			State1 = #state{streams=Streams1} = info(State0, StreamID, {response, 204, #{}, <<>>}),
 			State = maybe_skip_body(State1, Stream, Reason),
 			#stream{state=StreamState} = lists:keyfind(StreamID, #stream.id, Streams1),
-			stream_call_terminate(StreamID, Reason, StreamState),
+			stream_call_terminate(StreamID, Reason, StreamState, State),
 			Children = cowboy_children:shutdown(Children0, StreamID),
 			State#state{streams=Streams, children=Children};
 		%% When a response was sent but not terminated, we need to close the stream.
@@ -1317,7 +1324,7 @@ stream_terminate(State0=#state{streams=Streams0, children=Children0}, StreamID,
 			State1 = #state{streams=Streams1} = info(State0, StreamID, {data, fin, <<>>}),
 			State = maybe_skip_body(State1, Stream, Reason),
 			#stream{state=StreamState} = lists:keyfind(StreamID, #stream.id, Streams1),
-			stream_call_terminate(StreamID, Reason, StreamState),
+			stream_call_terminate(StreamID, Reason, StreamState, State),
 			Children = cowboy_children:shutdown(Children0, StreamID),
 			State#state{streams=Streams, children=Children};
 		%% Unless there is still data in the buffer. We can however reset
@@ -1327,14 +1334,14 @@ stream_terminate(State0=#state{streams=Streams0, children=Children0}, StreamID,
 		%% because we are still sending data via the buffer. We will
 		%% reset the stream if necessary once the buffer is empty.
 		{value, Stream=#stream{state=StreamState, local=nofin}, Streams} ->
-			stream_call_terminate(StreamID, Reason, StreamState),
+			stream_call_terminate(StreamID, Reason, StreamState, State0),
 			Children = cowboy_children:shutdown(Children0, StreamID),
 			State0#state{streams=[Stream#stream{state=flush, local=flush}|Streams],
 				children=Children};
 		%% Otherwise we sent or received an RST_STREAM and/or the stream is already closed.
 		{value, Stream=#stream{state=StreamState}, Streams} ->
 			State = maybe_skip_body(State0, Stream, Reason),
-			stream_call_terminate(StreamID, Reason, StreamState),
+			stream_call_terminate(StreamID, Reason, StreamState, State),
 			Children = cowboy_children:shutdown(Children0, StreamID),
 			State#state{streams=Streams, children=Children};
 		%% The stream doesn't exist. This can occur for various reasons.
@@ -1355,13 +1362,13 @@ maybe_skip_body(State=#state{socket=Socket, transport=Transport},
 maybe_skip_body(State, _, _) ->
 	State.
 
-stream_call_terminate(StreamID, Reason, StreamState) ->
+stream_call_terminate(StreamID, Reason, StreamState, #state{opts=Opts}) ->
 	try
 		cowboy_stream:terminate(StreamID, Reason, StreamState)
 	catch Class:Exception ->
-		cowboy_stream:report_error(terminate,
+		cowboy:log(cowboy_stream:make_error_log(terminate,
 			[StreamID, Reason, StreamState],
-			Class, Exception, erlang:get_stacktrace())
+			Class, Exception, erlang:get_stacktrace()), Opts)
 	end.
 
 %% System callbacks.