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<h1 class="lined-header"><span>cowboy_http2(3)</span></h1>
<h2 id="_name">Name</h2>
<p>cowboy_http2 - HTTP/2</p>
<h2 id="_description">Description</h2>
<p>The module <code>cowboy_http2</code> implements HTTP/2 as a Ranch protocol.</p>
<h2 id="_options">Options</h2>
<!-- @todo Might be worth moving cowboy_clear/tls/stream_h options-->
<!-- to their respective manual, when they are added.-->
<div class="listingblock"><div class="content"><!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><b><font color="#000000">opts</font></b>() <font color="#990000">::</font> #{
<font color="#0000FF">active_n</font> <font color="#990000">=></font> <b><font color="#000000">pos_integer</font></b>(),
<font color="#0000FF">connection_type</font> <font color="#990000">=></font> <font color="#FF6600">worker</font> | <font color="#FF6600">supervisor</font>,
<font color="#0000FF">connection_window_margin_size</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">connection_window_update_threshold</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">enable_connect_protocol</font> <font color="#990000">=></font> <b><font color="#000000">boolean</font></b>(),
<font color="#0000FF">goaway_initial_timeout</font> <font color="#990000">=></font> <b><font color="#000000">timeout</font></b>(),
<font color="#0000FF">goaway_complete_timeout</font> <font color="#990000">=></font> <b><font color="#000000">timeout</font></b>(),
<font color="#0000FF">idle_timeout</font> <font color="#990000">=></font> <b><font color="#000000">timeout</font></b>(),
<font color="#0000FF">inactivity_timeout</font> <font color="#990000">=></font> <b><font color="#000000">timeout</font></b>(),
<font color="#0000FF">initial_connection_window_size</font> <font color="#990000">=></font> <font color="#993399">65535</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">initial_stream_window_size</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">linger_timeout</font> <font color="#990000">=></font> <b><font color="#000000">timeout</font></b>(),
<font color="#0000FF">logger</font> <font color="#990000">=></font> <b><font color="#000000">module</font></b>(),
<font color="#0000FF">max_concurrent_streams</font> <font color="#990000">=></font> <b><font color="#000000">non_neg_integer</font></b>() | <font color="#FF6600">infinity</font>,
<font color="#0000FF">max_connection_buffer_size</font> <font color="#990000">=></font> <b><font color="#000000">non_neg_integer</font></b>(),
<font color="#0000FF">max_connection_window_size</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">max_decode_table_size</font> <font color="#990000">=></font> <b><font color="#000000">non_neg_integer</font></b>(),
<font color="#0000FF">max_encode_table_size</font> <font color="#990000">=></font> <b><font color="#000000">non_neg_integer</font></b>(),
<font color="#0000FF">max_frame_size_received</font> <font color="#990000">=></font> <font color="#993399">16384</font><font color="#990000">..</font><font color="#993399">16777215</font>,
<font color="#0000FF">max_frame_size_sent</font> <font color="#990000">=></font> <font color="#993399">16384</font><font color="#990000">..</font><font color="#993399">16777215</font> | <font color="#FF6600">infinity</font>,
<font color="#0000FF">max_received_frame_rate</font> <font color="#990000">=></font> {<b><font color="#000000">pos_integer</font></b>(), <b><font color="#000000">timeout</font></b>()},
<font color="#0000FF">max_reset_stream_rate</font> <font color="#990000">=></font> {<b><font color="#000000">pos_integer</font></b>(), <b><font color="#000000">timeout</font></b>()},
<font color="#0000FF">max_stream_buffer_size</font> <font color="#990000">=></font> <b><font color="#000000">non_neg_integer</font></b>(),
<font color="#0000FF">max_stream_window_size</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">preface_timeout</font> <font color="#990000">=></font> <b><font color="#000000">timeout</font></b>(),
<font color="#0000FF">proxy_header</font> <font color="#990000">=></font> <b><font color="#000000">boolean</font></b>(),
<font color="#0000FF">sendfile</font> <font color="#990000">=></font> <b><font color="#000000">boolean</font></b>(),
<font color="#0000FF">settings_timeout</font> <font color="#990000">=></font> <b><font color="#000000">timeout</font></b>(),
<font color="#0000FF">stream_handlers</font> <font color="#990000">=></font> [<b><font color="#000000">module</font></b>()],
<font color="#0000FF">stream_window_data_threshold</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">stream_window_margin_size</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>,
<font color="#0000FF">stream_window_update_threshold</font> <font color="#990000">=></font> <font color="#993399">0</font><font color="#990000">..</font><font color="#993399">16#7fffffff</font>
}</tt></pre>
</div></div>
<p>Configuration for the HTTP/2 protocol.</p>
<p>This configuration is passed to Cowboy when starting listeners using <code>cowboy:start_clear/3</code> or <code>cowboy:start_tls/3</code> functions.</p>
<p>It can be updated without restarting listeners using the Ranch functions <code>ranch:get_protocol_options/1</code> and <code>ranch:set_protocol_options/2</code>.</p>
<p>The default value is given next to the option name:</p>
<dl><dt>active_n (100)</dt>
<dd><p>The number of packets Cowboy will request from the socket at once. This can be used to tweak the performance of the server. Higher values reduce the number of times Cowboy need to request more packets from the port driver at the expense of potentially higher memory being used.</p>
</dd>
<dt>connection_type (supervisor)</dt>
<dd><p>Whether the connection process also acts as a supervisor.</p>
</dd>
<dt>connection_window_margin_size (65535)</dt>
<dd><p>Extra amount in bytes to be added to the window size when updating the connection window. This is used to ensure that there is always some space available in the window.</p>
</dd>
<dt>connection_window_update_threshold (163840)</dt>
<dd><p>The connection window will only get updated when its size becomes lower than this threshold, in bytes. This is to avoid sending too many <code>WINDOW_UPDATE</code> frames.</p>
</dd>
<dt>enable_connect_protocol (false)</dt>
<dd><p>Whether to enable the extended CONNECT method to allow protocols like Websocket to be used over an HTTP/2 stream. This option is experimental and disabled by default.</p>
</dd>
<dt>goaway_initial_timeout (1000)</dt>
<dd><p>Time in ms to wait for any in-flight stream creations before stopping to accept new streams on an existing connection during a graceful shutdown.</p>
</dd>
<dt>goaway_complete_timeout (3000)</dt>
<dd><p>Time in ms to wait for ongoing streams to complete before closing the connection during a graceful shutdown.</p>
</dd>
<dt>idle_timeout (60000)</dt>
<dd><p>Time in ms with no data received before Cowboy closes the connection.</p>
</dd>
<dt>inactivity_timeout (300000)</dt>
<dd><p>Time in ms with nothing received at all before Cowboy closes the connection.</p>
</dd>
<dt>initial_connection_window_size (65535)</dt>
<dd><p>Initial window size in bytes for the connection. This is the total amount of data (from request bodies for example) that may be buffered by the connection across all streams before the user code explicitly requests it.</p>
<p>Note that this value cannot be lower than the default.</p>
</dd>
<dt>initial_stream_window_size (65535)</dt>
<dd><p>Initial window size in bytes for new streams. This is the total amount of data (from request bodies for example) that may be buffered by a single stream before the user code explicitly requests it.</p>
</dd>
<dt>linger_timeout (1000)</dt>
<dd><p>Time in ms that Cowboy will wait when closing the connection. This is necessary to avoid the TCP reset problem as described in the <a href="https://tools.ietf.org/html/rfc7230#section-6.6">section 6.6 of RFC7230</a>. In HTTP/2's case the GOAWAY message might also be lost when closing the connection immediately.</p>
</dd>
<dt>logger (error_logger)</dt>
<dd><p>The module that will be used to write log messages.</p>
</dd>
<dt>max_concurrent_streams (infinity)</dt>
<dd><p>Maximum number of concurrent streams allowed on the connection.</p>
</dd>
<dt>max_connection_buffer_size (16000000)</dt>
<dd><p>Maximum size of all stream buffers for this connection, in bytes. This is a soft limit used to apply backpressure to handlers that send data faster than the HTTP/2 connection allows.</p>
</dd>
<dt>max_connection_window_size (16#7fffffff)</dt>
<dd><p>Maximum connection window size in bytes. This is used as an upper bound when calculating the window size, either when reading the request body or receiving said body.</p>
</dd>
<dt>max_decode_table_size (4096)</dt>
<dd><p>Maximum header table size in bytes used by the decoder. This is the value advertised to the client. The client can then choose a header table size equal or lower to the advertised value.</p>
</dd>
<dt>max_encode_table_size (4096)</dt>
<dd><p>Maximum header table size in bytes used by the encoder. The server will compare this value to what the client advertises and choose the smallest one as the encoder's header table size.</p>
</dd>
<dt>max_frame_size_received (16384)</dt>
<dd><p>Maximum size in bytes of the frames received by the server. This value is advertised to the remote endpoint which can then decide to use any value lower or equal for its frame sizes.</p>
</dd>
<dt>max_frame_size_sent (infinity)</dt>
<dd><p>Maximum size in bytes of the frames sent by the server. This option allows setting an upper limit to the frame sizes instead of blindly following the client's advertised maximum.</p>
<p>Note that actual frame sizes may be lower than the limit when there is not enough space left in the flow control window.</p>
</dd>
<dt>max_received_frame_rate ({10000, 10000})</dt>
<dd><p>Maximum frame rate allowed per connection. The rate is expressed as a tuple <code>{NumFrames, TimeMs}</code> indicating how many frames are allowed over the given time period. This is similar to a supervisor restart intensity/period.</p>
</dd>
<dt>max_reset_stream_rate ({10, 10000})</dt>
<dd><p>Maximum reset stream rate per connection. This can be used to protect against misbehaving or malicious peers that do not follow the protocol, leading to the server resetting streams, by limiting the number of streams that can be reset over a certain time period. The rate is expressed as a tuple <code>{NumResets, TimeMs}</code>. This is similar to a supervisor restart intensity/period.</p>
</dd>
<dt>max_stream_buffer_size (8000000)</dt>
<dd><p>Maximum stream buffer size in bytes. This is a soft limit used to apply backpressure to handlers that send data faster than the HTTP/2 connection allows.</p>
</dd>
<dt>max_stream_window_size (16#7fffffff)</dt>
<dd><p>Maximum stream window size in bytes. This is used as an upper bound when calculating the window size, either when reading the request body or receiving said body.</p>
</dd>
<dt>preface_timeout (5000)</dt>
<dd><p>Time in ms Cowboy is willing to wait for the connection preface.</p>
</dd>
<dt>proxy_header (false)</dt>
<dd><p>Whether incoming connections have a PROXY protocol header. The proxy information will be passed forward via the <code>proxy_header</code> key of the Req object.</p>
</dd>
<dt>sendfile (true)</dt>
<dd><p>Whether the sendfile syscall may be used. It can be useful to disable it on systems where the syscall has a buggy implementation, for example under VirtualBox when using shared folders.</p>
</dd>
<dt>settings_timeout (5000)</dt>
<dd><p>Time in ms Cowboy is willing to wait for a SETTINGS ack.</p>
</dd>
<dt>stream_handlers ([cowboy_stream_h])</dt>
<dd><p>Ordered list of stream handlers that will handle all stream events.</p>
</dd>
<dt>stream_window_data_threshold (16384)</dt>
<dd><p>Window threshold in bytes below which Cowboy will not attempt to send data, with one exception. When Cowboy has data to send and the window is high enough, Cowboy will always send the data, regardless of this option.</p>
</dd>
<dt>stream_window_margin_size (65535)</dt>
<dd><p>Extra amount in bytes to be added to the window size when updating a stream's window. This is used to ensure that there is always some space available in the window.</p>
</dd>
<dt>stream_window_update_threshold (163840)</dt>
<dd><p>A stream's window will only get updated when its size becomes lower than this threshold, in bytes. This is to avoid sending too many <code>WINDOW_UPDATE</code> frames.</p>
</dd>
</dl>
<h2 id="_changelog">Changelog</h2>
<ul><li><strong>2.9</strong>: The <code>goaway_initial_timeout</code> and <code>goaway_complete_timeout</code> options were added.
</li>
<li><strong>2.8</strong>: The <code>active_n</code> option was added.
</li>
<li><strong>2.8</strong>: The <code>linger_timeout</code> option was added.
</li>
<li><strong>2.8</strong>: The <code>max_received_frame_rate</code> default value has been multiplied by 10 as the default was too low.
</li>
<li><strong>2.7</strong>: Add the options <code>connection_window_margin_size</code>, <code>connection_window_update_threshold</code>, <code>max_connection_window_size</code>, <code>max_stream_window_size</code>, <code>stream_window_margin_size</code> and <code>stream_window_update_threshold</code> to configure behavior on sending WINDOW_UPDATE frames; <code>max_connection_buffer_size</code> and <code>max_stream_buffer_size</code> to apply backpressure when sending data too fast; <code>max_received_frame_rate</code> and <code>max_reset_stream_rate</code> to protect against various flood scenarios; and <code>stream_window_data_threshold</code> to control how small the DATA frames that Cowboy sends can get.
</li>
<li><strong>2.7</strong>: The <code>logger</code> option was added.
</li>
<li><strong>2.6</strong>: The <code>proxy_header</code> and <code>sendfile</code> options were added.
</li>
<li><strong>2.4</strong>: Add the options <code>initial_connection_window_size</code>, <code>initial_stream_window_size</code>, <code>max_concurrent_streams</code>, <code>max_decode_table_size</code>, <code>max_encode_table_size</code>, <code>max_frame_size_received</code>, <code>max_frame_size_sent</code> and <code>settings_timeout</code> to configure HTTP/2 SETTINGS and related behavior.
</li>
<li><strong>2.4</strong>: Add the experimental option <code>enable_connect_protocol</code>.
</li>
<li><strong>2.0</strong>: Protocol introduced.
</li>
</ul>
<h2 id="_see_also">See also</h2>
<p><a href="..">cowboy(7)</a>, <a href="../cowboy_http">cowboy_http(3)</a>, <a href="../cowboy_websocket">cowboy_websocket(3)</a></p>
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