%% Copyright (c) 2011-2014, Loïc Hoguin <[email protected]>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
%% When using loop handlers, we are receiving data from the socket because we
%% want to know when the socket gets closed. This is generally not an issue
%% because these kinds of requests are generally not pipelined, and don't have
%% a body. If they do have a body, this body is often read in the
%% <em>init/2</em> callback and this is no problem. Otherwise, this data
%% accumulates in a buffer until we reach a certain threshold of 5000 bytes
%% by default. This can be configured through the <em>loop_max_buffer</em>
%% environment value. The request will be terminated with an
%% <em>{error, overflow}</em> reason if this threshold is reached.
-module(cowboy_loop).
-behaviour(cowboy_sub_protocol).
-export([upgrade/6]).
-export([loop/4]).
-callback init(Req, any())
-> {ok | module(), Req, any()}
| {module(), Req, any(), hibernate}
| {module(), Req, any(), timeout()}
| {module(), Req, any(), timeout(), hibernate}
when Req::cowboy_req:req().
-callback info(any(), Req, State)
-> {ok, Req, State}
| {ok, Req, State, hibernate}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-callback terminate(any(), cowboy_req:req(), any()) -> ok.
-optional_callbacks([terminate/3]).
-record(state, {
env :: cowboy_middleware:env(),
hibernate = false :: boolean(),
buffer_size = 0 :: non_neg_integer(),
max_buffer = 5000 :: non_neg_integer() | infinity,
timeout = infinity :: timeout(),
timeout_ref = undefined :: undefined | reference(),
resp_sent = false :: boolean()
}).
-spec upgrade(Req, Env, module(), any(), timeout(), run | hibernate)
-> {ok, Req, Env} | {suspend, module(), atom(), [any()]}
when Req::cowboy_req:req(), Env::cowboy_middleware:env().
upgrade(Req, Env, Handler, HandlerState, Timeout, run) ->
State = #state{env=Env, max_buffer=get_max_buffer(Env), timeout=Timeout},
State2 = timeout(State),
after_call(Req, State2, Handler, HandlerState);
upgrade(Req, Env, Handler, HandlerState, Timeout, hibernate) ->
% dbg:start(),
% dbg:tracer(),
% dbg:tpl(?MODULE, []),
% dbg:tpl(long_polling_h, []),
% dbg:tpl(loop_handler_body_h, []),
% dbg:tpl(cowboy_req, []),
% dbg:p(all, c),
State = #state{env=Env, max_buffer=get_max_buffer(Env), hibernate=true, timeout=Timeout},
State2 = timeout(State),
after_call(Req, State2, Handler, HandlerState).
get_max_buffer(#{loop_max_buffer := MaxBuffer}) -> MaxBuffer;
get_max_buffer(_) -> 5000.
%% Update the state if the response was sent in the callback.
after_call(Req, State=#state{resp_sent=false}, Handler,
HandlerState) ->
receive
{cowboy_req, resp_sent} ->
before_loop(Req, State#state{resp_sent=true}, Handler, HandlerState)
after 0 ->
before_loop(Req, State, Handler, HandlerState)
end;
after_call(Req, State, Handler, HandlerState) ->
before_loop(Req, State, Handler, HandlerState).
before_loop(Req, State=#state{hibernate=true}, Handler, HandlerState) ->
%% @todo Yeah we can't get the socket anymore.
%% Everything changes since we are a separate process now.
%% Proper flow control at the connection level should be implemented
%% instead of what we have here.
% [Socket, Transport] = cowboy_req:get([socket, transport], Req),
% Transport:setopts(Socket, [{active, once}]),
{suspend, ?MODULE, loop, [Req, State#state{hibernate=false}, Handler, HandlerState]};
before_loop(Req, State, Handler, HandlerState) ->
%% Same here.
% [Socket, Transport] = cowboy_req:get([socket, transport], Req),
% Transport:setopts(Socket, [{active, once}]),
loop(Req, State, Handler, HandlerState).
%% Almost the same code can be found in cowboy_websocket.
timeout(State=#state{timeout=infinity}) ->
State#state{timeout_ref=undefined};
timeout(State=#state{timeout=Timeout,
timeout_ref=PrevRef}) ->
_ = case PrevRef of
undefined -> ignore;
PrevRef -> erlang:cancel_timer(PrevRef)
end,
TRef = erlang:start_timer(Timeout, self(), ?MODULE),
State#state{timeout_ref=TRef}.
-spec loop(Req, #state{}, module(), any())
-> {ok, Req, cowboy_middleware:env()} | {suspend, module(), atom(), [any()]}
when Req::cowboy_req:req().
loop(Req, State=#state{timeout_ref=TRef}, Handler, HandlerState) ->
receive
{timeout, TRef, ?MODULE} ->
terminate(Req, State, Handler, HandlerState, timeout);
{timeout, OlderTRef, ?MODULE} when is_reference(OlderTRef) ->
loop(Req, State, Handler, HandlerState);
Message ->
call(Req, State, Handler, HandlerState, Message)
end.
call(Req, State=#state{resp_sent=RespSent},
Handler, HandlerState, Message) ->
try Handler:info(Message, Req, HandlerState) of
{ok, Req2, HandlerState2} ->
after_call(Req2, State, Handler, HandlerState2);
{ok, Req2, HandlerState2, hibernate} ->
after_call(Req2, State#state{hibernate=true}, Handler, HandlerState2);
{stop, Req2, HandlerState2} ->
terminate(Req2, State, Handler, HandlerState2, stop)
catch Class:Reason ->
Stacktrace = erlang:get_stacktrace(),
if RespSent -> ok; true ->
cowboy_req:maybe_reply(Stacktrace, Req)
end,
cowboy_handler:terminate({crash, Class, Reason}, Req, HandlerState, Handler),
exit({cowboy_handler, [
{class, Class},
{reason, Reason},
{mfa, {Handler, info, 3}},
{stacktrace, Stacktrace},
{req, Req},
{state, HandlerState}
]})
end.
terminate(Req, #state{env=Env, timeout_ref=TRef},
Handler, HandlerState, Reason) ->
_ = case TRef of
undefined -> ignore;
TRef -> erlang:cancel_timer(TRef)
end,
flush_timeouts(),
Result = cowboy_handler:terminate(Reason, Req, HandlerState, Handler),
{ok, Req, [{result, Result}|Env]}.
flush_timeouts() ->
receive
{timeout, TRef, ?MODULE} when is_reference(TRef) ->
flush_timeouts()
after 0 ->
ok
end.
