Add timeout to cowboy_loop

LH: I have added a test that does both hibernate and timeout
    and fixed a related issue. I also tweaked the docs and tests.

doc/src/guide/loop_handlers.asciidoc

@@ -31,7 +31,10 @@ for plain HTTP handlers.
 The `init/2` function must return a `cowboy_loop` tuple to enable
 loop handler behavior. This tuple may optionally contain
 the atom `hibernate` to make the process enter hibernation
-until a message is received.
+until a message is received. Alternatively, the tuple may
+optionally contain a positive integer to create a `timeout`
+message when the process has not received messages for too
+long.
 
 This snippet enables the loop handler:
 
@@ -49,6 +52,14 @@ init(Req, State) ->
     {cowboy_loop, Req, State, hibernate}.
 ----
 
+This makes the process time out after 1000ms of idle time.
+
+[source,erlang]
+----
+init(Req, State) ->
+    {cowboy_loop, Req, State, 1000}.
+----
+
 === Receive loop
 
 Once initialized, Cowboy will wait for messages to arrive
@@ -123,3 +134,17 @@ messages received. This is done by returning the atom
 `hibernate` as part of the `loop` tuple callbacks normally
 return. Just add the atom at the end and Cowboy will hibernate
 accordingly.
+
+=== Idle timeout
+
+You may activate timeout events by returning a positive integer
+`N` as part of the `loop` tuple callbacks return. The default
+value is `infinity`. The `info` callback will be called with the
+atom `timeout` unless a message is received within `N` milliseconds:
+
+[source,erlang]
+----
+info(timeout, Req, State) ->
+    %% Do something...
+    {ok, Req, State, 1000}.
+----

doc/src/manual/cowboy_loop.asciidoc

@@ -28,11 +28,11 @@ Loop handlers implement the following interface:
 ----
 init(Req, State)
     -> {cowboy_loop, Req, State}
-     | {cowboy_loop, Req, State, hibernate}
+     | {cowboy_loop, Req, State, hibernate | timeout()}
 
 info(Info, Req, State)
     -> {ok, Req, State}
-     | {ok, Req, State, hibernate}
+     | {ok, Req, State, hibernate | timeout()}
      | {stop, Req, State}
 
 terminate(Reason, Req, State) -> ok  %% optional
@@ -69,7 +69,9 @@ stop::
 
 == Changelog
 
-* *2.0*: Loop handlers no longer need to handle overflow/timeouts.
+* *2.11*: A timeout may be returned instead of `hibernate`.
+          It functions the same way as the `gen_server` timeout.
+* *2.0*: Loop handlers no longer need to handle socket events.
 * *1.0*: Behavior introduced.
 
 == See also

src/cowboy_loop.erl

@@ -17,12 +17,15 @@
 
 -export([upgrade/4]).
 -export([upgrade/5]).
--export([loop/4]).
+-export([loop/5]).
 
 -export([system_continue/3]).
 -export([system_terminate/4]).
 -export([system_code_change/4]).
 
+%% From gen_server.
+-define(is_timeout(X), ((X) =:= infinity orelse (is_integer(X) andalso (X) >= 0))).
+
 -callback init(Req, any())
 	-> {ok | module(), Req, any()}
 	| {module(), Req, any(), any()}
@@ -41,40 +44,46 @@
 	-> {ok, Req, Env} | {suspend, ?MODULE, loop, [any()]}
 	when Req::cowboy_req:req(), Env::cowboy_middleware:env().
 upgrade(Req, Env, Handler, HandlerState) ->
-	loop(Req, Env, Handler, HandlerState).
+	loop(Req, Env, Handler, HandlerState, infinity).
 
--spec upgrade(Req, Env, module(), any(), hibernate)
+-spec upgrade(Req, Env, module(), any(), hibernate | timeout())
 	-> {suspend, ?MODULE, loop, [any()]}
 	when Req::cowboy_req:req(), Env::cowboy_middleware:env().
 upgrade(Req, Env, Handler, HandlerState, hibernate) ->
-	suspend(Req, Env, Handler, HandlerState).
+	suspend(Req, Env, Handler, HandlerState);
+upgrade(Req, Env, Handler, HandlerState, Timeout) when ?is_timeout(Timeout) ->
+	loop(Req, Env, Handler, HandlerState, Timeout).
 
--spec loop(Req, Env, module(), any())
+-spec loop(Req, Env, module(), any(), timeout())
 	-> {ok, Req, Env} | {suspend, ?MODULE, loop, [any()]}
 	when Req::cowboy_req:req(), Env::cowboy_middleware:env().
 %% @todo Handle system messages.
-loop(Req=#{pid := Parent}, Env, Handler, HandlerState) ->
+loop(Req=#{pid := Parent}, Env, Handler, HandlerState, Timeout) ->
 	receive
 		%% System messages.
 		{'EXIT', Parent, Reason} ->
 			terminate(Req, Env, Handler, HandlerState, Reason);
 		{system, From, Request} ->
 			sys:handle_system_msg(Request, From, Parent, ?MODULE, [],
-				{Req, Env, Handler, HandlerState});
+				{Req, Env, Handler, HandlerState, Timeout});
 		%% Calls from supervisor module.
 		{'$gen_call', From, Call} ->
 			cowboy_children:handle_supervisor_call(Call, From, [], ?MODULE),
-			loop(Req, Env, Handler, HandlerState);
+			loop(Req, Env, Handler, HandlerState, Timeout);
 		Message ->
-			call(Req, Env, Handler, HandlerState, Message)
+			call(Req, Env, Handler, HandlerState, Timeout, Message)
+	after Timeout ->
+		call(Req, Env, Handler, HandlerState, Timeout, timeout)
 	end.
 
-call(Req0, Env, Handler, HandlerState0, Message) ->
+call(Req0, Env, Handler, HandlerState0, Timeout, Message) ->
 	try Handler:info(Message, Req0, HandlerState0) of
 		{ok, Req, HandlerState} ->
-			loop(Req, Env, Handler, HandlerState);
+			loop(Req, Env, Handler, HandlerState, Timeout);
 		{ok, Req, HandlerState, hibernate} ->
 			suspend(Req, Env, Handler, HandlerState);
+		{ok, Req, HandlerState, NewTimeout} when ?is_timeout(NewTimeout) ->
+			loop(Req, Env, Handler, HandlerState, NewTimeout);
 		{stop, Req, HandlerState} ->
 			terminate(Req, Env, Handler, HandlerState, stop)
 	catch Class:Reason:Stacktrace ->
@@ -83,23 +92,23 @@ call(Req0, Env, Handler, HandlerState0, Message) ->
 	end.
 
 suspend(Req, Env, Handler, HandlerState) ->
-	{suspend, ?MODULE, loop, [Req, Env, Handler, HandlerState]}.
+	{suspend, ?MODULE, loop, [Req, Env, Handler, HandlerState, infinity]}.
 
 terminate(Req, Env, Handler, HandlerState, Reason) ->
 	Result = cowboy_handler:terminate(Reason, Req, HandlerState, Handler),
 	{ok, Req, Env#{result => Result}}.
 
 %% System callbacks.
 
--spec system_continue(_, _, {Req, Env, module(), any()})
+-spec system_continue(_, _, {Req, Env, module(), any(), timeout()})
 	-> {ok, Req, Env} | {suspend, ?MODULE, loop, [any()]}
 	when Req::cowboy_req:req(), Env::cowboy_middleware:env().
-system_continue(_, _, {Req, Env, Handler, HandlerState}) ->
-	loop(Req, Env, Handler, HandlerState).
+system_continue(_, _, {Req, Env, Handler, HandlerState, Timeout}) ->
+	loop(Req, Env, Handler, HandlerState, Timeout).
 
--spec system_terminate(any(), _, _, {Req, Env, module(), any()})
+-spec system_terminate(any(), _, _, {Req, Env, module(), any(), timeout()})
 	-> {ok, Req, Env} when Req::cowboy_req:req(), Env::cowboy_middleware:env().
-system_terminate(Reason, _, _, {Req, Env, Handler, HandlerState}) ->
+system_terminate(Reason, _, _, {Req, Env, Handler, HandlerState, _}) ->
 	terminate(Req, Env, Handler, HandlerState, Reason).
 
 -spec system_code_change(Misc, _, _, _) -> {ok, Misc}

test/handlers/loop_handler_timeout_hibernate_h.erl

@@ -0,0 +1,30 @@
+%% This module implements a loop handler that first
+%% sets a timeout, then hibernates, then ensures
+%% that the timeout initially set no longer triggers.
+%% If everything goes fine a 200 is returned. If the
+%% timeout triggers again a 299 is.
+
+-module(loop_handler_timeout_hibernate_h).
+
+-export([init/2]).
+-export([info/3]).
+-export([terminate/3]).
+
+init(Req, _) ->
+	self() ! message1,
+	{cowboy_loop, Req, undefined, 100}.
+
+info(message1, Req, State) ->
+	erlang:send_after(200, self(), message2),
+	{ok, Req, State, hibernate};
+info(message2, Req, State) ->
+	erlang:send_after(200, self(), message3),
+	%% Don't set a timeout now.
+	{ok, Req, State};
+info(message3, Req, State) ->
+	{stop, cowboy_req:reply(200, Req), State};
+info(timeout, Req, State) ->
+	{stop, cowboy_req:reply(<<"299 OK!">>, Req), State}.
+
+terminate(stop, _, _) ->
+	ok.

test/handlers/loop_handler_timeout_info_h.erl

@@ -0,0 +1,23 @@
+%% This module implements a loop handler that changes
+%% the timeout value to 500ms after the first message
+%% then sends itself another message after 1000ms.
+%% It is expected to timeout, that is, reply a 299.
+
+-module(loop_handler_timeout_info_h).
+
+-export([init/2]).
+-export([info/3]).
+-export([terminate/3]).
+
+init(Req, _) ->
+	self() ! message,
+	{cowboy_loop, Req, undefined}.
+
+info(message, Req, State) ->
+	erlang:send_after(200, self(), message),
+	{ok, Req, State, 100};
+info(timeout, Req, State) ->
+	{stop, cowboy_req:reply(<<"299 OK!">>, Req), State}.
+
+terminate(stop, _, _) ->
+	ok.

test/handlers/loop_handler_timeout_init_h.erl

@@ -0,0 +1,23 @@
+%% This module implements a loop handler that reads
+%% the request query for a timeout value, then sends
+%% itself a message after 1000ms. It replies a 200 when
+%% the message does not timeout and a 299 otherwise.
+
+-module(loop_handler_timeout_init_h).
+
+-export([init/2]).
+-export([info/3]).
+-export([terminate/3]).
+
+init(Req, _) ->
+	#{timeout := Timeout} = cowboy_req:match_qs([{timeout, int}], Req),
+	erlang:send_after(200, self(), message),
+	{cowboy_loop, Req, undefined, Timeout}.
+
+info(message, Req, State) ->
+	{stop, cowboy_req:reply(200, Req), State};
+info(timeout, Req, State) ->
+	{stop, cowboy_req:reply(<<"299 OK!">>, Req), State}.
+
+terminate(stop, _, _) ->
+	ok.

test/loop_handler_SUITE.erl

@@ -40,7 +40,10 @@ init_dispatch(_) ->
 	cowboy_router:compile([{'_', [
 		{"/long_polling", long_polling_h, []},
 		{"/loop_body", loop_handler_body_h, []},
-		{"/loop_timeout", loop_handler_timeout_h, []}
+		{"/loop_request_timeout", loop_handler_timeout_h, []},
+		{"/loop_timeout_init", loop_handler_timeout_init_h, []},
+		{"/loop_timeout_info", loop_handler_timeout_info_h, []},
+		{"/loop_timeout_hibernate", loop_handler_timeout_hibernate_h, []}
 	]}]).
 
 %% Tests.
@@ -79,6 +82,31 @@ long_polling_pipeline(Config) ->
 request_timeout(Config) ->
 	doc("Ensure that the request_timeout isn't applied when a request is ongoing."),
 	ConnPid = gun_open(Config),
-	Ref = gun:get(ConnPid, "/loop_timeout", [{<<"accept-encoding">>, <<"gzip">>}]),
+	Ref = gun:get(ConnPid, "/loop_request_timeout", [{<<"accept-encoding">>, <<"gzip">>}]),
 	{response, nofin, 200, _} = gun:await(ConnPid, Ref, 10000),
 	ok.
+
+timeout_hibernate(Config) ->
+	doc("Ensure that loop handler idle timeouts don't trigger after hibernate is returned."),
+	ConnPid = gun_open(Config),
+	Ref = gun:get(ConnPid, "/loop_timeout_hibernate", [{<<"accept-encoding">>, <<"gzip">>}]),
+	{response, fin, 200, _} = gun:await(ConnPid, Ref),
+	ok.
+
+timeout_info(Config) ->
+	doc("Ensure that loop handler idle timeouts trigger on time when set in info/3."),
+	ConnPid = gun_open(Config),
+	Ref = gun:get(ConnPid, "/loop_timeout_info", [{<<"accept-encoding">>, <<"gzip">>}]),
+	{response, fin, 299, _} = gun:await(ConnPid, Ref),
+	ok.
+
+timeout_init(Config) ->
+	doc("Ensure that loop handler idle timeouts trigger on time when set in init/2."),
+	ConnPid = gun_open(Config),
+	Ref = gun:get(ConnPid, "/loop_timeout_init?timeout=300",
+		[{<<"accept-encoding">>, <<"gzip">>}]),
+	{response, fin, 200, _} = gun:await(ConnPid, Ref),
+	Ref2 = gun:get(ConnPid, "/loop_timeout_init?timeout=100",
+		[{<<"accept-encoding">>, <<"gzip">>}]),
+	{response, fin, 299, _} = gun:await(ConnPid, Ref2),
+	ok.

test/sys_SUITE.erl

@@ -659,7 +659,7 @@ sys_get_state_loop(Config) ->
 	timer:sleep(100),
 	SupPid = get_remote_pid_tcp(Socket),
 	[{_, Pid, _, _}] = supervisor:which_children(SupPid),
-	{Req, Env, long_polling_sys_h, undefined} = sys:get_state(Pid),
+	{Req, Env, long_polling_sys_h, undefined, infinity} = sys:get_state(Pid),
 	#{pid := _, streamid := _} = Req,
 	#{dispatch := _} = Env,
 	ok.
@@ -784,7 +784,7 @@ sys_replace_state_loop(Config) ->
 	timer:sleep(100),
 	SupPid = get_remote_pid_tcp(Socket),
 	[{_, Pid, _, _}] = supervisor:which_children(SupPid),
-	{Req, Env, long_polling_sys_h, undefined} = sys:replace_state(Pid, fun(S) -> S end),
+	{Req, Env, long_polling_sys_h, undefined, infinity} = sys:replace_state(Pid, fun(S) -> S end),
 	#{pid := _, streamid := _} = Req,
 	#{dispatch := _} = Env,
 	ok.