aboutsummaryrefslogtreecommitdiffstats
path: root/src/cowboy_loop.erl
blob: e162417bb574c2121adf0638a57bf1089aedfa2d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
%% 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{buffer_size=NbBytes,
		max_buffer=Threshold, timeout_ref=TRef,
		resp_sent=RespSent}, 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 ->
%					_ = if RespSent -> ok; true ->
%						cowboy_req:reply(500, Req)
%					end,
%					cowboy_handler:terminate({error, overflow}, Req, HandlerState, Handler),
%					exit(normal);
%				true ->
%					Req2 = cowboy_req:append_buffer(Data, Req),
%					State2 = timeout(State#state{buffer_size=NbBytes2}),
%					before_loop(Req2, State2, Handler, HandlerState)
%			end;
%		{Closed, Socket} ->
%			terminate(Req, State, Handler, HandlerState, {error, closed});
%		{Error, Socket, Reason} ->
%			terminate(Req, State, Handler, HandlerState, {error, Reason});
		{timeout, TRef, ?MODULE} ->
			after_loop(Req, State, Handler, HandlerState, timeout);
		{timeout, OlderTRef, ?MODULE} when is_reference(OlderTRef) ->
			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,
			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} ->
			after_loop(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.

%% 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.
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(Req2, State, Handler, HandlerState, Reason).

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.