From 5e006be01fb9af2cbb6b62bec695a2c160733cf4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Mon, 10 Oct 2011 17:27:52 +0200 Subject: Add support for loops in standard HTTP handlers Now init/3 can return one of the following values to enable loops: - {loop, Req, State} - {loop, Req, State, hibernate} - {loop, Req, State, Timeout} - {loop, Req, State, Timeout, hibernate} Returning one of these tuples will activate looping in the HTTP handler. When looping, handle/2 is never called. Instead, Cowboy will listen for Erlang messages and forward them to the info/3 function of the handler. If a timeout is defined, Cowboy will also close the connection when no message has been received for Timeout milliseconds. The info/3 function is defined as info(Msg, Req, State). It can return either of the following tuples: - {ok, Req, State} - {loop, Req, State} - {loop, Req, State, hibernate} The first one ends the connection, calling terminate/2 before closing. The others continue the loop. Loops are useful when writing long-polling handlers that need to wait and don't expect to receive anything. Therefore it is recommended to set a timeout to close the connection if nothing arrives after a while and to enable hibernate everywhere. Normal HTTP handlers shouldn't need to use this and as such info/3 was made optional. --- src/cowboy_http_protocol.erl | 83 +++++++++++++++++++++++++++++++++++++++----- 1 file changed, 75 insertions(+), 8 deletions(-) (limited to 'src/cowboy_http_protocol.erl') diff --git a/src/cowboy_http_protocol.erl b/src/cowboy_http_protocol.erl index 50860d7..290007b 100644 --- a/src/cowboy_http_protocol.erl +++ b/src/cowboy_http_protocol.erl @@ -33,7 +33,7 @@ -behaviour(cowboy_protocol). -export([start_link/4]). %% API. --export([init/4, parse_request/1]). %% FSM. +-export([init/4, parse_request/1, handler_loop/3]). %% FSM. -include("include/http.hrl"). -include_lib("eunit/include/eunit.hrl"). @@ -47,7 +47,10 @@ req_empty_lines = 0 :: integer(), max_empty_lines :: integer(), timeout :: timeout(), - buffer = <<>> :: binary() + buffer = <<>> :: binary(), + hibernate = false :: boolean(), + loop_timeout = infinity :: timeout(), + loop_timeout_ref :: undefined | reference() }). %% API. @@ -204,7 +207,18 @@ handler_init(Req, State=#state{listener=ListenerPid, transport=Transport, handler={Handler, Opts}}) -> try Handler:init({Transport:name(), http}, Req, Opts) of {ok, Req2, HandlerState} -> - handler_loop(HandlerState, Req2, State); + handler_handle(HandlerState, Req2, State); + {loop, Req, HandlerState} -> + handler_before_loop(HandlerState, Req, State); + {loop, Req, HandlerState, hibernate} -> + handler_before_loop(HandlerState, Req, + State#state{hibernate=true}); + {loop, Req, HandlerState, Timeout} -> + handler_before_loop(HandlerState, Req, + State#state{loop_timeout=Timeout}); + {loop, Req, HandlerState, Timeout, hibernate} -> + handler_before_loop(HandlerState, Req, + State#state{hibernate=true, loop_timeout=Timeout}); {shutdown, Req2, HandlerState} -> handler_terminate(HandlerState, Req2, State); %% @todo {upgrade, transport, Module} @@ -220,8 +234,8 @@ handler_init(Req, State=#state{listener=ListenerPid, [Handler, Class, Reason, Opts, Req, erlang:get_stacktrace()]) end. --spec handler_loop(any(), #http_req{}, #state{}) -> ok. -handler_loop(HandlerState, Req, State=#state{handler={Handler, Opts}}) -> +-spec handler_handle(any(), #http_req{}, #state{}) -> ok. +handler_handle(HandlerState, Req, State=#state{handler={Handler, Opts}}) -> try Handler:handle(Req, HandlerState) of {ok, Req2, HandlerState2} -> next_request(HandlerState2, Req2, State) @@ -237,7 +251,61 @@ handler_loop(HandlerState, Req, State=#state{handler={Handler, Opts}}) -> terminate(State) end. --spec handler_terminate(any(), #http_req{}, #state{}) -> ok | error. +%% We don't listen for Transport closes because that would force us +%% to receive data and buffer it indefinitely. +-spec handler_before_loop(any(), #http_req{}, #state{}) -> ok. +handler_before_loop(HandlerState, Req, State=#state{hibernate=true}) -> + State2 = handler_loop_timeout(State), + erlang:hibernate(?MODULE, handler_loop, [HandlerState, Req, State2]); +handler_before_loop(HandlerState, Req, State) -> + State2 = handler_loop_timeout(State), + handler_loop(HandlerState, Req, State2). + +%% Almost the same code can be found in cowboy_http_websocket. +-spec handler_loop_timeout(#state{}) -> #state{}. +handler_loop_timeout(State=#state{loop_timeout=infinity}) -> + State#state{loop_timeout_ref=undefined}; +handler_loop_timeout(State=#state{loop_timeout=Timeout, + loop_timeout_ref=PrevRef}) -> + _ = case PrevRef of undefined -> ignore; PrevRef -> + erlang:cancel_timer(PrevRef) end, + TRef = make_ref(), + erlang:send_after(Timeout, self(), {?MODULE, timeout, TRef}), + State#state{loop_timeout_ref=TRef}. + +-spec handler_loop(any(), #http_req{}, #state{}) -> ok. +handler_loop(HandlerState, Req, State=#state{loop_timeout_ref=TRef}) -> + receive + {?MODULE, timeout, TRef} -> + next_request(HandlerState, Req, State); + {?MODULE, timeout, OlderTRef} when is_reference(OlderTRef) -> + handler_loop(HandlerState, Req, State); + Message -> + handler_call(HandlerState, Req, State, Message) + end. + +-spec handler_call(any(), #http_req{}, #state{}, any()) -> ok. +handler_call(HandlerState, Req, State=#state{handler={Handler, Opts}}, + Message) -> + try Handler:info(Message, Req, HandlerState) of + {ok, Req2, HandlerState2} -> + next_request(HandlerState2, Req2, State); + {loop, Req2, HandlerState2} -> + handler_before_loop(HandlerState2, Req2, State); + {loop, Req2, HandlerState2, hibernate} -> + handler_before_loop(HandlerState2, Req2, + State#state{hibernate=true}) + catch Class:Reason -> + error_logger:error_msg( + "** Handler ~p terminating in info/3~n" + " for the reason ~p:~p~n" + "** Options were ~p~n** Handler state was ~p~n" + "** Request was ~p~n** Stacktrace: ~p~n~n", + [Handler, Class, Reason, Opts, + HandlerState, Req, erlang:get_stacktrace()]) + end. + +-spec handler_terminate(any(), #http_req{}, #state{}) -> ok. handler_terminate(HandlerState, Req, #state{handler={Handler, Opts}}) -> try Handler:terminate(Req#http_req{resp_state=locked}, HandlerState) @@ -248,8 +316,7 @@ handler_terminate(HandlerState, Req, #state{handler={Handler, Opts}}) -> "** Options were ~p~n** Handler state was ~p~n" "** Request was ~p~n** Stacktrace: ~p~n~n", [Handler, Class, Reason, Opts, - HandlerState, Req, erlang:get_stacktrace()]), - error + HandlerState, Req, erlang:get_stacktrace()]) end. -spec next_request(any(), #http_req{}, #state{}) -> ok. -- cgit v1.2.3