%% 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.
%% @doc Handler middleware.
%%
%% Execute the handler given by the <em>handler</em> and <em>handler_opts</em>
%% environment values. The result of this execution is added to the
%% environment under the <em>result</em> value.
%%
%% 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/3</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.
%%
%% @see cowboy_http_handler
-module(cowboy_handler).
-behaviour(cowboy_middleware).
-export([execute/2]).
-export([handler_loop/4]).
-record(state, {
env :: cowboy_middleware:env(),
hibernate = false :: boolean(),
loop_buffer_size = 0 :: non_neg_integer(),
loop_max_buffer = 5000 :: non_neg_integer() | infinity,
loop_timeout = infinity :: timeout(),
loop_timeout_ref = undefined :: undefined | reference(),
resp_sent = false :: boolean()
}).
%% @private
-spec execute(Req, Env)
-> {ok, Req, Env} | {error, 500, Req}
| {suspend, ?MODULE, handler_loop, [any()]}
when Req::cowboy_req:req(), Env::cowboy_middleware:env().
execute(Req, Env) ->
{_, Handler} = lists:keyfind(handler, 1, Env),
{_, HandlerOpts} = lists:keyfind(handler_opts, 1, Env),
MaxBuffer = case lists:keyfind(loop_max_buffer, 1, Env) of
false -> 5000;
{_, MaxBuffer0} -> MaxBuffer0
end,
handler_init(Req, #state{env=Env, loop_max_buffer=MaxBuffer},
Handler, HandlerOpts).
-spec handler_init(Req, #state{}, module(), any())
-> {ok, Req, cowboy_middleware:env()}
| {error, 500, Req} | {suspend, module(), atom(), [any()]}
when Req::cowboy_req:req().
handler_init(Req, State, Handler, HandlerOpts) ->
Transport = cowboy_req:get(transport, Req),
try Handler:init({Transport:name(), http}, Req, HandlerOpts) of
{ok, Req2, HandlerState} ->
handler_handle(Req2, State, Handler, HandlerState);
{loop, Req2, HandlerState} ->
handler_after_callback(Req2, State, Handler, HandlerState);
{loop, Req2, HandlerState, hibernate} ->
handler_after_callback(Req2, State#state{hibernate=true},
Handler, HandlerState);
{loop, Req2, HandlerState, Timeout} ->
State2 = handler_loop_timeout(State#state{loop_timeout=Timeout}),
handler_after_callback(Req2, State2, Handler, HandlerState);
{loop, Req2, HandlerState, Timeout, hibernate} ->
State2 = handler_loop_timeout(State#state{
hibernate=true, loop_timeout=Timeout}),
handler_after_callback(Req2, State2, Handler, HandlerState);
{shutdown, Req2, HandlerState} ->
terminate_request(Req2, State, Handler, HandlerState,
{normal, shutdown});
%% @todo {upgrade, transport, Module}
{upgrade, protocol, Module} ->
upgrade_protocol(Req, State, Handler, HandlerOpts, Module);
{upgrade, protocol, Module, Req2, HandlerOpts2} ->
upgrade_protocol(Req2, State, Handler, HandlerOpts2, Module)
catch Class:Reason ->
cowboy_req:maybe_reply(500, Req),
erlang:Class([
{reason, Reason},
{mfa, {Handler, init, 3}},
{stacktrace, erlang:get_stacktrace()},
{req, cowboy_req:to_list(Req)},
{opts, HandlerOpts}
])
end.
-spec upgrade_protocol(Req, #state{}, module(), any(), module())
-> {ok, Req, Env}
| {suspend, module(), atom(), any()}
| {halt, Req}
| {error, cowboy:http_status(), Req}
when Req::cowboy_req:req(), Env::cowboy_middleware:env().
upgrade_protocol(Req, #state{env=Env},
Handler, HandlerOpts, Module) ->
Module:upgrade(Req, Env, Handler, HandlerOpts).
-spec handler_handle(Req, #state{}, module(), any())
-> {ok, Req, cowboy_middleware:env()}
| {error, 500, Req}
when Req::cowboy_req:req().
handler_handle(Req, State, Handler, HandlerState) ->
try Handler:handle(Req, HandlerState) of
{ok, Req2, HandlerState2} ->
terminate_request(Req2, State, Handler, HandlerState2,
{normal, shutdown})
catch Class:Reason ->
cowboy_req:maybe_reply(500, Req),
handler_terminate(Req, Handler, HandlerState, Reason),
erlang:Class([
{reason, Reason},
{mfa, {Handler, handle, 2}},
{stacktrace, erlang:get_stacktrace()},
{req, cowboy_req:to_list(Req)},
{state, HandlerState}
])
end.
%% Update the state if the response was sent in the callback.
-spec handler_after_callback(Req, #state{}, module(), any())
-> {ok, Req, cowboy_middleware:env()}
| {error, 500, Req} | {suspend, module(), atom(), [any()]}
when Req::cowboy_req:req().
handler_after_callback(Req, State=#state{resp_sent=false}, Handler,
HandlerState) ->
receive
{cowboy_req, resp_sent} ->
handler_before_loop(Req, State#state{resp_sent=true}, Handler,
HandlerState)
after 0 ->
handler_before_loop(Req, State, Handler, HandlerState)
end;
handler_after_callback(Req, State, Handler, HandlerState) ->
handler_before_loop(Req, State, Handler, HandlerState).
%% We don't listen for Transport closes because that would force us
%% to receive data and buffer it indefinitely.
-spec handler_before_loop(Req, #state{}, module(), any())
-> {ok, Req, cowboy_middleware:env()}
| {error, 500, Req} | {suspend, module(), atom(), [any()]}
when Req::cowboy_req:req().
handler_before_loop(Req, State=#state{hibernate=true}, Handler, HandlerState) ->
[Socket, Transport] = cowboy_req:get([socket, transport], Req),
Transport:setopts(Socket, [{active, once}]),
{suspend, ?MODULE, handler_loop,
[Req, State#state{hibernate=false}, Handler, HandlerState]};
handler_before_loop(Req, State, Handler, HandlerState) ->
[Socket, Transport] = cowboy_req:get([socket, transport], Req),
Transport:setopts(Socket, [{active, once}]),
handler_loop(Req, State, Handler, HandlerState).
%% Almost the same code can be found in cowboy_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 = erlang:start_timer(Timeout, self(), ?MODULE),
State#state{loop_timeout_ref=TRef}.
%% @private
-spec handler_loop(Req, #state{}, module(), any())
-> {ok, Req, cowboy_middleware:env()}
| {error, 500, Req} | {suspend, module(), atom(), [any()]}
when Req::cowboy_req:req().
handler_loop(Req, State=#state{loop_buffer_size=NbBytes,
loop_max_buffer=Threshold, loop_timeout_ref=TRef},
Handler, HandlerState) ->
[Socket, Transport] = cowboy_req:get([socket, transport], Req),
{OK, Closed, Error} = Transport:messages(),
receive
{OK, Socket, Data} ->
NbBytes2 = NbBytes + byte_size(Data),
if NbBytes2 > Threshold ->
_ = handler_terminate(Req, Handler, HandlerState,
{error, overflow}),
cowboy_req:maybe_reply(500, Req),
exit(normal);
true ->
Req2 = cowboy_req:append_buffer(Data, Req),
State2 = handler_loop_timeout(State#state{
loop_buffer_size=NbBytes2}),
handler_before_loop(Req2, State2, Handler, HandlerState)
end;
{Closed, Socket} ->
terminate_request(Req, State, Handler, HandlerState,
{error, closed});
{Error, Socket, Reason} ->
terminate_request(Req, State, Handler, HandlerState,
{error, Reason});
{timeout, TRef, ?MODULE} ->
handler_after_loop(Req, State, Handler, HandlerState,
{normal, timeout});
{timeout, OlderTRef, ?MODULE} when is_reference(OlderTRef) ->
handler_loop(Req, State, Handler, HandlerState);
Message ->
%% We set the socket back to {active, false} mode in case
%% the handler is going to call recv. We also flush any
%% data received after that and put it into the buffer.
%% We do not check the size here, if data keeps coming
%% we'll error out on the next packet received.
Transport:setopts(Socket, [{active, false}]),
Req2 = receive {OK, Socket, Data} ->
cowboy_req:append_buffer(Data, Req)
after 0 ->
Req
end,
handler_call(Req2, State, Handler, HandlerState, Message)
end.
-spec handler_call(Req, #state{}, module(), any(), any())
-> {ok, Req, cowboy_middleware:env()}
| {error, 500, Req} | {suspend, module(), atom(), [any()]}
when Req::cowboy_req:req().
handler_call(Req, State=#state{resp_sent=RespSent},
Handler, HandlerState, Message) ->
try Handler:info(Message, Req, HandlerState) of
{ok, Req2, HandlerState2} ->
handler_after_loop(Req2, State, Handler, HandlerState2,
{normal, shutdown});
{loop, Req2, HandlerState2} ->
handler_after_callback(Req2, State, Handler, HandlerState2);
{loop, Req2, HandlerState2, hibernate} ->
handler_after_callback(Req2, State#state{hibernate=true},
Handler, HandlerState2)
catch Class:Reason ->
if RespSent ->
ok;
true ->
cowboy_req:maybe_reply(500, Req)
end,
handler_terminate(Req, Handler, HandlerState, Reason),
erlang:Class([
{reason, Reason},
{mfa, {Handler, info, 3}},
{stacktrace, erlang:get_stacktrace()},
{req, cowboy_req:to_list(Req)},
{state, HandlerState}
])
end.
%% It is sometimes important to make a socket passive as it was initially
%% and as it is expected to be by cowboy_protocol, right after we're done
%% with loop handling. The browser may freely pipeline a bunch of requests
%% if previous one was, say, a JSONP long-polling request.
-spec handler_after_loop(Req, #state{}, module(), any(),
{normal, timeout | shutdown} | {error, atom()}) ->
{ok, Req, cowboy_middleware:env()} when Req::cowboy_req:req().
handler_after_loop(Req, State, Handler, HandlerState, Reason) ->
[Socket, Transport] = cowboy_req:get([socket, transport], Req),
Transport:setopts(Socket, [{active, false}]),
{OK, _Closed, _Error} = Transport:messages(),
Req2 = receive
{OK, Socket, Data} ->
cowboy_req:append_buffer(Data, Req)
after 0 ->
Req
end,
terminate_request(Req2, State, Handler, HandlerState, Reason).
-spec terminate_request(Req, #state{}, module(), any(),
{normal, timeout | shutdown} | {error, atom()}) ->
{ok, Req, cowboy_middleware:env()} when Req::cowboy_req:req().
terminate_request(Req, #state{env=Env, loop_timeout_ref=TRef},
Handler, HandlerState, Reason) ->
HandlerRes = handler_terminate(Req, Handler, HandlerState, Reason),
_ = case TRef of
undefined -> ignore;
TRef -> erlang:cancel_timer(TRef)
end,
flush_timeouts(),
{ok, Req, [{result, HandlerRes}|Env]}.
-spec handler_terminate(cowboy_req:req(), module(), any(),
{normal, timeout | shutdown} | {error, atom()}) -> ok.
handler_terminate(Req, Handler, HandlerState, Reason) ->
try
Handler:terminate(Reason, cowboy_req:lock(Req), HandlerState)
catch Class:Reason2 ->
erlang:Class([
{reason, Reason2},
{mfa, {Handler, terminate, 3}},
{stacktrace, erlang:get_stacktrace()},
{req, cowboy_req:to_list(Req)},
{state, HandlerState},
{terminate_reason, Reason}
])
end.
-spec flush_timeouts() -> ok.
flush_timeouts() ->
receive
{timeout, TRef, ?MODULE} when is_reference(TRef) ->
flush_timeouts()
after 0 ->
ok
end.
