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   <title>Configuring HTTP/2</title><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><meta name="keywords" content="jetty, servlet, servlet-api, cometd, http, websocket, eclipse, maven, java, server, software"><link rel="home" href="index.html" title="Jetty"><link rel="up" href="http2.html" title="Chapter&nbsp;16.&nbsp;HTTP/2"><link rel="prev" href="http2-enabling.html" title="Enabling HTTP/2"><link rel="next" href="http2-configuring-push.html" title="Configuring HTTP/2 Push"><link xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" rel="shortcut icon" href="images/favicon.ico"><link rel="stylesheet" href="css/highlighter/foundation.css"><script src="js/highlight.pack.js"></script><script>
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      </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="http2-configuring"></a>Configuring HTTP/2</h2></div></div></div><p>Enabling the HTTP/2 module in the Jetty server does not create a HTTP/2 specific connector, but rather it adds a HTTP/2 Connection factory to an
existing connector.
Thus configuring HTTP/2 is a combination of configuring common properties on the connector and HTTP/2 specific properties on the connection factory.
The modules and XML files involved can be seen with the following commands:</p><div class="screenexample"><pre class="screen">$ java -jar $JETTY_HOME/start.jar --list-modules
    ...
    1) alpn-impl  &lt;transitive&gt;
    ...
    2) http            ${jetty.base}/start.d/http.ini
    2) ssl             ${jetty.base}/start.d/ssl.ini
    3) alpn            ${jetty.base}/start.d/alpn.ini
    3) http2c          ${jetty.base}/start.d/http2c.ini
    ...
    4) http2           ${jetty.base}/start.d/http2.ini
    5) https           ${jetty.base}/start.d/https.ini

$ java -jar $JETTY_HOME/start.jar --list-config
 ...
 ${jetty.home}/etc/jetty-ssl.xml
 ${jetty.home}/etc/jetty-ssl-context.xml
 ${jetty.home}/etc/jetty-alpn.xml
 ${jetty.home}/etc/jetty-http2c.xml
 ${jetty.home}/etc/jetty-http.xml
 ...
 ${jetty.home}/etc/jetty-http2.xml
 ${jetty.home}/etc/jetty-https.xml</pre></div><p>The common properties associated with connectors (host,port, timeouts, etc.) can be set in the module ini files (or <code class="literal">start.ini</code> if <code class="literal">--add-to-start</code> was used): <code class="literal">${jetty.base}/start.d/http.ini</code> and <code class="literal">${jetty.base}/start.d/ssl.ini</code>.
These properties are instantiated in the associated XML files: <code class="literal">${jetty.home}/etc/jetty-http.xml</code>; <code class="literal">${jetty.home}/etc/jetty-ssl.xml</code>, plus the SSL keystore is instantiated in <code class="literal">${jetty.home}/etc/jetty-ssl-context.xml</code>.</p><div class="blockquote"><blockquote class="blockquote"><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title"><i class="fa fa-asterisk" aria-hidden="true"></i> Note</h3><p>If you are planning to edit XML files, make sure to copy them to your <code class="literal">{$jetty.base}/etc/</code> directory before doing so.
The XML files that come with the Jetty distribution should <span class="strong"><strong>not</strong></span> be modified directly.</p></div></blockquote></div><p>HTTP/2 specific properties can be set in the module ini files: <code class="literal">${jetty.base}/start.d/http2.ini</code> and <code class="literal">${jetty.base}/start.d/http2c.ini</code>, which are instantiated in the associated XML files: <code class="literal">${jetty.home}/etc/jetty-http2.xml</code>; <code class="literal">${jetty.home}/etc/jetty-http2c.xml</code>, respectively.
Currently there are very few HTTP/2 configuration properties and the default values are reasonable:</p><div class="table"><a name="d0e18372"></a><p class="title"><b>Table&nbsp;16.1.&nbsp;HTTP/2 Configuration Properties</b></p><div class="table-contents"><table class="table" summary="HTTP/2 Configuration Properties" border="1"><colgroup><col class="col_1"><col class="col_2"></colgroup><thead><tr><th align="left" valign="top">Property</th><th align="left" valign="top">Description</th></tr></thead><tbody><tr><td align="left" valign="top"><p>jetty.http2.maxConcurrentStreams</p></td><td align="left" valign="top"><p>The maximum number of concurrently open streams allowed on a single HTTP/2 connection (default 128). Larger values increase parallelism but cost a memory commitment.</p></td></tr><tr><td align="left" valign="top"><p>jetty.http2.initialSessionRecvWindow</p></td><td align="left" valign="top"><p>The initial receive flow control window size for a new session (default 1048576). Larger values may allow greater throughput but also risk head of line blocking if TCP/IP flow control is triggered.</p></td></tr><tr><td align="left" valign="top"><p>jetty.http2.initialStreamRecvWindow</p></td><td align="left" valign="top"><p>The initial receive flow control window size for a new stream (default 524288). Larger values may allow greater throughput but also risk head of line blocking if TCP/IP flow control is triggered.</p></td></tr></tbody></table></div></div><br class="table-break"></div><script type="text/javascript">
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