Ensure HTTP/1.1 Websocket resets the trap_exit flag

While we are identified as a supervisor in the tree,
we no longer manage children processes at that point,
so do not need to trap exit signals. Users can still
enable trap_exit if they prefer to.

doc/src/manual/cowboy_websocket.asciidoc

@@ -285,6 +285,7 @@ normal circumstances if necessary.
 
 == Changelog
 
+* *2.11*: HTTP/1.1 Websocket no longer traps exits by default.
 * *2.8*: The `active_n` option was added.
 * *2.7*: The commands based interface has been documented.
          The old interface is now deprecated.

src/cowboy_http.erl

@@ -1212,11 +1212,13 @@ commands(State0=#state{ref=Ref, parent=Parent, socket=Socket, transport=Transpor
 		_ -> State
 	end,
 	#stream{state=StreamState} = lists:keyfind(StreamID, #stream.id, Streams),
-	%% @todo We need to shutdown processes here first.
 	stream_call_terminate(StreamID, switch_protocol, StreamState, State),
 	%% Terminate children processes and flush any remaining messages from the mailbox.
 	cowboy_children:terminate(Children),
 	flush(Parent),
+	%% Turn off the trap_exit process flag
+	%% since this process will no longer be a supervisor.
+	process_flag(trap_exit, false),
 	Protocol:takeover(Parent, Ref, Socket, Transport, Opts, Buffer, InitialState);
 %% Set options dynamically.
 commands(State0=#state{overriden_opts=Opts},

test/handlers/ws_init_h.erl

@@ -36,7 +36,10 @@ do_websocket_init(State=reply_many_hibernate) ->
 do_websocket_init(State=reply_many_close) ->
 	{[{text, "Hello"}, close], State};
 do_websocket_init(State=reply_many_close_hibernate) ->
-	{[{text, "Hello"}, close], State, hibernate}.
+	{[{text, "Hello"}, close], State, hibernate};
+do_websocket_init(State=reply_trap_exit) ->
+	Text = "trap_exit: " ++ atom_to_list(element(2, process_info(self(), trap_exit))),
+	{[{text, Text}, close], State, hibernate}.
 
 websocket_handle(_, State) ->
 	{[], State}.

test/ws_SUITE.erl

@@ -341,6 +341,7 @@ ws_first_frame_with_handshake(Config) ->
 	{ok, <<1:1, 0:3, 1:4, 0:1, 5:7, "Hello">>} = gen_tcp:recv(Socket, 0, 6000),
 	ok.
 
+%% @todo Move these tests to ws_handler_SUITE.
 ws_init_return_ok(Config) ->
 	doc("Handler does nothing."),
 	{ok, Socket, _} = do_handshake("/ws_init?ok", Config),

test/ws_handler_SUITE.erl

@@ -50,6 +50,7 @@ init_dispatch(Name) ->
 		{"/init", ws_init_commands_h, RunOrHibernate},
 		{"/handle", ws_handle_commands_h, RunOrHibernate},
 		{"/info", ws_info_commands_h, RunOrHibernate},
+		{"/trap_exit", ws_init_h, RunOrHibernate},
 		{"/active", ws_active_commands_h, RunOrHibernate},
 		{"/deflate", ws_deflate_commands_h, RunOrHibernate},
 		{"/set_options", ws_set_options_commands_h, RunOrHibernate},
@@ -211,6 +212,13 @@ do_many_frames_then_close_frame(Config, Path) ->
 	{ok, close} = receive_ws(ConnPid, StreamRef),
 	gun_down(ConnPid).
 
+websocket_init_trap_exit_false(Config) ->
+	doc("The trap_exit process flag must be set back to false before "
+		"the connection is taken over by Websocket."),
+	{ok, ConnPid, StreamRef} = gun_open_ws(Config, "/trap_exit?reply_trap_exit", []),
+	{ok, {text, <<"trap_exit: false">>}} = receive_ws(ConnPid, StreamRef),
+	ok.
+
 websocket_active_false(Config) ->
 	doc("The {active, false} command stops receiving data from the socket. "
 		"The {active, true} command reenables it."),