Cowboy handlers proably exit, not being logged or reported anywhere

josevalim · April 20, 2021, 5:25pm

I have investigated this a bit, the issue is here:

ninenines/cowboy/blob/master/src/cowboy_stream_h.erl#L127-L141


info(StreamID, Info={'EXIT', Pid, normal}, State=#state{pid=Pid}) ->
	do_info(StreamID, Info, [stop], State);
info(StreamID, Info={'EXIT', Pid, {{request_error, Reason, _HumanReadable}, _}},
		State=#state{pid=Pid}) ->
	Status = case Reason of
		timeout -> 408;
		payload_too_large -> 413;
		_ -> 400
	end,
	%% @todo Headers? Details in body? Log the crash? More stuff in debug only?
	do_info(StreamID, Info, [
		{error_response, Status, #{<<"content-length">> => <<"0">>}, <<>>},
		stop
	], State);
info(StreamID, Exit={'EXIT', Pid, {Reason, Stacktrace}}, State=#state{ref=Ref, pid=Pid}) ->

Cowboy is not handling a {'EXIT', Pid, Whatever}, which is the format of exit reasons from linked processes. I would open up an issue on Cowboy and ask if they would consider adding a catch clause.