aboutsummaryrefslogtreecommitdiffstats
path: root/src/cowboy_handler.erl
blob: ac95de5b2c015d0dee2a8be2bfe88ddea4866fea (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
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
%% 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.