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
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="">
<meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara">
<meta name="generator" content="Hugo 0.16" />
<title>Nine Nines: cowboy_handler(3)</title>
<link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'>
<link href="/css/bootstrap.min.css" rel="stylesheet">
<link href="/css/99s.css" rel="stylesheet">
<link rel="shortcut icon" href="/img/ico/favicon.ico">
<link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png">
<link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png">
<link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png">
</head>
<body class="">
<header id="page-head">
<div id="topbar" class="container">
<div class="row">
<div class="span2">
<h1 id="logo"><a href="/" title="99s">99s</a></h1>
</div>
<div class="span10">
<div id="side-header">
<nav>
<ul>
<li><a title="Hear my thoughts" href="/articles">Articles</a></li>
<li><a title="Watch my talks" href="/talks">Talks</a></li>
<li class="active"><a title="Read the docs" href="/docs">Documentation</a></li>
<li><a title="Request my services" href="/services">Consulting & Training</a></li>
</ul>
</nav>
<ul id="social">
<li>
<a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a>
</li>
<li>
<a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a>
</li>
<li>
<a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a>
</li>
</ul>
</div>
</div>
</div>
</div>
</header>
<div id="contents" class="two_col">
<div class="container">
<div class="row">
<div id="docs" class="span9 maincol">
<h1 class="lined-header"><span>cowboy_handler(3)</span></h1>
<div class="sect1">
<h2 id="_name">Name</h2>
<div class="sectionbody">
<div class="paragraph"><p>cowboy_handler - handler middleware and behaviour</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">Description</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <code>cowboy_handler</code> middleware executes the handler passed
through the environment values <code>handler</code> and <code>handler_opts</code>,
and adds the result of this execution to the environment as
the value <code>result</code>, indicating that the request has been
handled and received a response.</p></div>
<div class="paragraph"><p>Environment input:</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
handler = module()
</dt>
<dd>
<p>
Handler to be executed.
</p>
</dd>
<dt class="hdlist1">
handler_opts = any()
</dt>
<dd>
<p>
Options to be passed to the handler.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>Environment output:</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
result = ok
</dt>
<dd>
<p>
Result of the request.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>This module also defines the <code>cowboy_handler</code> behaviour that
defines the basic interface for handlers. All Cowboy handlers
implement at least the <code>init/2</code> callback, and may implement
the <code>terminate/3</code> callback optionally.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_terminate_reasons">Terminate reasons</h2>
<div class="sectionbody">
<div class="paragraph"><p>The following values may be received as the terminate reason
in the optional <code>terminate/3</code> callback. Different handler types
may define additional terminate reasons.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
normal
</dt>
<dd>
<p>
The connection was closed normally.
</p>
</dd>
<dt class="hdlist1">
{crash, Class, Reason}
</dt>
<dd>
<p>
A crash occurred in the handler. <code>Class</code> and <code>Reason</code> can be
used to obtain more information about the crash. The function
<code>erlang:get_stacktrace/0</code> can also be called to obtain the
stacktrace of the process when the crash occurred.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_callbacks">Callbacks</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_init_req_opts_8594_ok_req_state_module_req_state_module_req_state_hibernate_timeout_module_req_state_timeout_hibernate">init(Req, Opts) → {ok, Req, State} | {Module, Req, State} | {Module, Req, State, hibernate | Timeout} | {Module, Req, State, Timeout, hibernate}</h3>
<div class="dlist"><dl>
<dt class="hdlist1">
Req = cowboy_req:req()
</dt>
<dd>
<p>
The Req object.
</p>
</dd>
<dt class="hdlist1">
Opts = any()
</dt>
<dd>
<p>
Handler options.
</p>
</dd>
<dt class="hdlist1">
State = any()
</dt>
<dd>
<p>
Handler state.
</p>
</dd>
<dt class="hdlist1">
Module = module()
</dt>
<dd>
<p>
Module of the sub-protocol to use.
</p>
</dd>
<dt class="hdlist1">
Timeout = timeout()
</dt>
<dd>
<p>
Timeout passed to the sub-protocol, when applicable.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>Process the request.</p></div>
<div class="paragraph"><p>This function can be used to switch to an alternate handler
type by returning the name of the module to be used, along
with a few options.</p></div>
<div class="paragraph"><p>For basic handlers this is the function where the response
should be sent. If no response is sent, Cowboy will ensure
that a <code>204 No Content</code> response is sent.</p></div>
<div class="paragraph"><p>A crash in this callback will result in <code>terminate/3</code> being
called if it is defined, with the <code>State</code> argument set to
the value of <code>Opts</code> originally given to the <code>init/2</code> callback.</p></div>
</div>
<div class="sect2">
<h3 id="_terminate_reason_req_state_8594_ok">terminate(Reason, Req, State) → ok</h3>
<div class="dlist"><dl>
<dt class="hdlist1">
Reason = any()
</dt>
<dd>
<p>
Reason for termination.
</p>
</dd>
<dt class="hdlist1">
Req = cowboy_req:req()
</dt>
<dd>
<p>
The Req object.
</p>
</dd>
<dt class="hdlist1">
State = any()
</dt>
<dd>
<p>
Handler state.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>Perform any necessary cleanup of the state.</p></div>
<div class="paragraph"><p>This callback should release any resource currently in use,
clear any active timer and reset the process to its original
state, as it might be reused for future requests sent on the
same connection. Typical plain HTTP handlers rarely need to
use it.</p></div>
<div class="paragraph"><p>A crash in this callback or an invalid return value will
result in the closing of the connection and the termination
of the process.</p></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_exports">Exports</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_terminate_reason_req_state_handler_8594_ok">terminate(Reason, Req, State, Handler) → ok</h3>
<div class="dlist"><dl>
<dt class="hdlist1">
Reason = any()
</dt>
<dd>
<p>
Reason for termination.
</p>
</dd>
<dt class="hdlist1">
Req = cowboy_req:req()
</dt>
<dd>
<p>
The Req object.
</p>
</dd>
<dt class="hdlist1">
State = any()
</dt>
<dd>
<p>
Handler state.
</p>
</dd>
<dt class="hdlist1">
Handler = module()
</dt>
<dd>
<p>
Handler module.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>Call the optional <code>terminate/3</code> callback if it exists.</p></div>
<div class="paragraph"><p>This function should always be called at the end of the execution
of a handler, to give it a chance to clean up or perform
miscellaneous operations.</p></div>
</div>
</div>
</div>
</div>
<div class="span3 sidecol">
<h3>
Cowboy
2.0
Function Reference
</h3>
<ul>
<li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li>
</ul>
<h4 id="docs-nav">Navigation</h4>
<h4>Version select</h4>
<ul>
<li><a href="/docs/en/cowboy/1.0/manual">1.0</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">2.0</a></li>
</ul>
</div>
</div>
</div>
</div>
<footer>
<div class="container">
<div class="row">
<div class="span6">
<p id="scroll-top"><a href="#">↑ Scroll to top</a></p>
<nav>
<ul>
<li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li>
</ul>
</nav>
</div>
<div class="span6 credits">
<p><img src="/img/footer_logo.png"></p>
<p>Copyright © Loïc Hoguin 2012-2016</p>
</div>
</div>
</div>
</footer>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script src="/js/bootstrap-carousel.js"></script>
<script src="/js/bootstrap-dropdown.js"></script>
<script src="/js/custom.js"></script>
</body>
</html>
|
