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
|
<!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">
<title>Nine Nines: Streams</title>
<link href='https://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'>
<link href="/css/99s.css?r=7" 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="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>Streams</span></h1>
<p>A stream is the set of messages that form an HTTP request/response pair.</p>
<p>The term stream comes from HTTP/2. In Cowboy, it is also used when talking about HTTP/1.1 or HTTP/1.0. It should not be confused with streaming the request or response body.</p>
<p>All versions of HTTP allow clients to initiate streams. HTTP/2 is the only one also allowing servers, through its server push feature. Both client and server-initiated streams go through the same process in Cowboy.</p>
<h2 id="_stream_handlers">Stream handlers</h2>
<p>Stream handlers must implement five different callbacks. Four of them are directly related; one is special.</p>
<p>All callbacks receives the stream ID as first argument.</p>
<p>Most of them can return a list of commands to be executed by Cowboy. When callbacks are chained, it is possible to intercept and modify these commands. This can be useful for modifying responses for example.</p>
<p>The <code>init/3</code> callback is invoked when a new request comes in. It receives the Req object and the protocol options for this listener.</p>
<p>The <code>data/4</code> callback is invoked when data from the request body is received. It receives both this data and a flag indicating whether more is to be expected.</p>
<p>The <code>info/3</code> callback is invoked when an Erlang message is received for this stream. They will typically be messages sent by the request process.</p>
<p>Finally the <code>terminate/3</code> callback is invoked with the terminate reason for the stream. The return value is ignored. Note that as with all terminate callbacks in Erlang, there is no strong guarantee that it will be called.</p>
<p>The special callback <code>early_error/5</code> is called when an error occurs before the request headers were fully received and Cowboy is sending a response. It receives the partial Req object, the error reason, the protocol options and the response Cowboy will send. This response must be returned, possibly modified.</p>
<h2 id="_built_in_handlers">Built-in handlers</h2>
<p>Cowboy comes with two handlers.</p>
<p><code>cowboy_stream_h</code> is the default stream handler. It is the core of much of the functionality of Cowboy. All chains of stream handlers should call it last.</p>
<p><code>cowboy_compress_h</code> will automatically compress responses when possible. It is not enabled by default. It is a good example for writing your own handlers that will modify responses.</p>
<nav style="margin:1em 0">
<a style="float:left" href="https://ninenines.eu/docs/en/cowboy/2.3/guide/ws_handlers/">
Websocket handlers
</a>
<a style="float:right" href="https://ninenines.eu/docs/en/cowboy/2.3/guide/middlewares/">
Middlewares
</a>
</nav>
</div>
<div class="span3 sidecol">
<h3>
Cowboy
2.3
User Guide
</h3>
<ul>
<li><a href="/docs/en/cowboy/2.3/guide">User Guide</a></li>
<li><a href="/docs/en/cowboy/2.3/manual">Function Reference</a></li>
</ul>
<h4 id="docs-nav">Navigation</h4>
<h4>Version select</h4>
<ul>
<li><a href="/docs/en/cowboy/2.8/guide">2.8</a></li>
<li><a href="/docs/en/cowboy/2.7/guide">2.7</a></li>
<li><a href="/docs/en/cowboy/2.6/guide">2.6</a></li>
<li><a href="/docs/en/cowboy/2.5/guide">2.5</a></li>
<li><a href="/docs/en/cowboy/2.4/guide">2.4</a></li>
<li><a href="/docs/en/cowboy/2.3/guide">2.3</a></li>
</ul>
<h3 id="_like_my_work__donate">Like my work? Donate!</h3>
<p>Donate to Loïc Hoguin because his work on Cowboy, Ranch, Gun and Erlang.mk is fantastic:</p>
<form action="https://www.paypal.com/cgi-bin/webscr" method="post" style="display:inline">
<input type="hidden" name="cmd" value="_donations">
<input type="hidden" name="business" value="[email protected]">
<input type="hidden" name="lc" value="FR">
<input type="hidden" name="item_name" value="Loic Hoguin">
<input type="hidden" name="item_number" value="99s">
<input type="hidden" name="currency_code" value="EUR">
<input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHosted">
<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.paypalobjects.com/fr_FR/i/scr/pixel.gif" width="1" height="1">
</form><p>Recurring payment options are also available via <a href="https://github.com/sponsors/essen">GitHub Sponsors</a>. These funds are used to cover the recurring expenses like food, dedicated servers or domain names.</p>
</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 2012-2018</p>
</div>
</div>
</div>
</footer>
<script src="/js/custom.js"></script>
</body>
</html>
|
