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Submitted by: Justin Vreeland <j_vreeland apple.com> Github: closes #407 git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1915531 13f79535-47bb-0310-9956-ffa450edef68
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1101 lines
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head>
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<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" />
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<!--
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This file is generated from xml source: DO NOT EDIT
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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-->
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<title>mod_http2 - Apache HTTP Server Version 2.5</title>
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<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
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<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
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<script src="../style/scripts/prettify.min.js" type="text/javascript">
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</script>
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<link href="../images/favicon.ico" rel="shortcut icon" /></head>
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<body>
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<div id="page-header">
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
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<p class="apache">Apache HTTP Server Version 2.5</p>
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<img alt="" src="../images/feather.png" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<div id="path">
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.5</a> > <a href="./">Modules</a></div>
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<div id="page-content">
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<div id="preamble"><h1>Apache Module mod_http2</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_http2.html" title="English"> en </a> |
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<a href="../fr/mod/mod_http2.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p>
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</div>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Support for the HTTP/2 transport layer</td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>http2_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_http2.c</td></tr>
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<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.17 and later</td></tr></table>
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<h3>Summary</h3>
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<p>This module provides HTTP/2 (<a href="https://tools.ietf.org/html/rfc7540">RFC 7540</a>)
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support for the Apache HTTP Server.</p>
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<p>This module relies on <a href="http://nghttp2.org/">libnghttp2</a>
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to provide the core http/2 engine.</p>
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<p>You must enable HTTP/2 via <code class="directive"><a href="../mod/core.html#protocols">Protocols</a></code>
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in order to use the functionality described in this document. The
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HTTP/2 protocol <a href="https://http2.github.io/faq/#does-http2-require-encryption">does not require</a> the use of encryption so two schemes are available:
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<code>h2</code> (HTTP/2 over TLS) and <code>h2c</code> (HTTP/2 over TCP).</p>
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<p>Two useful configuration schemes are:</p>
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<div class="note"><h3>HTTP/2 in a VirtualHost context (TLS only)</h3>
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<pre class="prettyprint lang-config">Protocols h2 http/1.1</pre>
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<p>Allows HTTP/2 negotiation (h2) via TLS ALPN in a secure
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<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>.
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HTTP/2 preamble checking (Direct mode, see <code class="directive"><a href="#h2direct">H2Direct</a></code>) is disabled by default for <code>h2</code>.</p>
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</div>
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<div class="note"><h3>HTTP/2 in a Server context (TLS and cleartext)</h3>
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<pre class="prettyprint lang-config">Protocols h2 h2c http/1.1</pre>
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<p>Allows HTTP/2 negotiation (h2) via TLS ALPN for secure
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<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>. Allows
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HTTP/2 cleartext negotiation (h2c) upgrading from an initial HTTP/1.1
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connection or via HTTP/2 preamble checking (Direct mode, see
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<code class="directive"><a href="#h2direct">H2Direct</a></code>).</p>
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||
</div>
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<p>Refer to the official <a href="https://http2.github.io/faq">HTTP/2 FAQ</a>
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for any doubt about the protocol.</p>
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</div>
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<div id="quickview"><h3>Topics</h3>
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<ul id="topics">
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<li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it works</a></li>
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</ul><h3 class="directives">Directives</h3>
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<ul id="toc">
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<li><img alt="" src="../images/down.gif" /> <a href="#h2copyfiles">H2CopyFiles</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2direct">H2Direct</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2earlyhint">H2EarlyHint</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#h2earlyhints">H2EarlyHints</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#h2maxdataframelen">H2MaxDataFrameLen</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#h2maxsessionstreams">H2MaxSessionStreams</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2maxworkeridleseconds">H2MaxWorkerIdleSeconds</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#h2maxworkers">H2MaxWorkers</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2minworkers">H2MinWorkers</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2moderntlsonly">H2ModernTLSOnly</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2outputbuffering">H2OutputBuffering</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2padding">H2Padding</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2proxyrequests">H2ProxyRequests</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2push">H2Push</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2pushdiarysize">H2PushDiarySize</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2pushpriority">H2PushPriority</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2pushresource">H2PushResource</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#h2serializeheaders">H2SerializeHeaders</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2streammaxmemsize">H2StreamMaxMemSize</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2streamtimeout">H2StreamTimeout</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2tlscooldownsecs">H2TLSCoolDownSecs</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2tlswarmupsize">H2TLSWarmUpSize</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2upgrade">H2Upgrade</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2websockets">H2WebSockets</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#h2windowsize">H2WindowSize</a></li>
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</ul>
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<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_http2">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_http2">Report a bug</a></li></ul><h3>See also</h3>
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<ul class="seealso">
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<li><a href="#comments_section">Comments</a></li></ul></div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="how-it-works" id="how-it-works">How it works</a> <a title="Permanent link" href="#how-it-works" class="permalink">¶</a></h2>
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<h3><a name="dimensioning" id="dimensioning">HTTP/2 Dimensioning</a></h3>
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<p>
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Enabling HTTP/2 on your Apache Server has impact on the resource
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consumption and if you have a busy site, you may need to consider
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carefully the implications.
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</p>
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<p>
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The first noticeable thing after enabling HTTP/2 is that your server
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processes will start additional threads. The reason for this is that
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HTTP/2 gives all requests that it receives to its own <em>Worker</em>
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threads for processing, collects the results and streams them out
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to the client.
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</p>
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<p>
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In the current implementation, these workers use a separate thread
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pool from the MPM workers that you might be familiar with. This is
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just how things are right now and not intended to be like this forever.
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(It might be forever for the 2.4.x release line, though.) So, HTTP/2
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workers, or shorter H2Workers, will not show up in <code class="module"><a href="../mod/mod_status.html">mod_status</a></code>. They
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are also not counted against directives such as <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code>. However
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they take <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code>
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as default if you have not configured something
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else via <code class="directive"><a href="#h2minworkers">H2MinWorkers</a></code> and
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<code class="directive"><a href="#h2maxworkers">H2MaxWorkers</a></code>.
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</p>
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<p>
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Another thing to watch out for is is memory consumption. Since HTTP/2
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keeps more state on the server to manage all the open request, priorities
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for and dependencies between them, it will always need more memory
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than HTTP/1.1 processing. There are three directives which steer the
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memory footprint of a HTTP/2 connection:
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<code class="directive"><a href="#h2maxsessionstreams">H2MaxSessionStreams</a></code>,
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<code class="directive"><a href="#h2windowsize">H2WindowSize</a></code> and
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<code class="directive"><a href="#h2streammaxmemsize">H2StreamMaxMemSize</a></code>.
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</p>
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<p>
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<code class="directive"><a href="#h2maxsessionstreams">H2MaxSessionStreams</a></code> limits the
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number of parallel requests that a client can make on a HTTP/2 connection.
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It depends on your site how many you should allow. The default is 100 which
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is plenty and unless you run into memory problems, I would keep it this
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way. Most requests that browsers send are GETs without a body, so they
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use up only a little bit of memory until the actual processing starts.
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</p>
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<p>
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<code class="directive"><a href="#h2windowsize">H2WindowSize</a></code> controls how much
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the client is allowed to send as body of a request, before it waits
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for the server to encourage more. Or, the other way around, it is the
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amount of request body data the server needs to be able to buffer. This
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is per request.
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</p>
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<p>
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And last, but not least, <code class="directive"><a href="#h2streammaxmemsize">H2StreamMaxMemSize</a></code>
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controls how much response data shall be buffered. The request sits in
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a H2Worker thread and is producing data, the HTTP/2 connection tries
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||
to send this to the client. If the client does not read fast enough,
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the connection will buffer this amount of data and then suspend the
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H2Worker.
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</p>
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<h3><a name="misdirected" id="misdirected">Multiple Hosts and Misdirected Requests</a></h3>
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<p>
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Many sites use the same TLS certificate for multiple virtual hosts. The
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certificate either has a wildcard name, such as '*.example.org' or carries
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several alternate names. Browsers using HTTP/2 will recognize that and reuse
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an already opened connection for such hosts.
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</p>
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<p>
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||
While this is great for performance, it comes at a price: such vhosts
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need more care in their configuration. The problem is that you will have
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multiple requests for multiple hosts on the same TLS connection. And that
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makes renegotiation impossible, in face the HTTP/2 standard forbids it.
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||
</p>
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||
<p>
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So, if you have several virtual hosts using the same certificate and
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want to use HTTP/2 for them, you need to make sure that all vhosts have
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exactly the same SSL configuration. You need the same protocol,
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ciphers and settings for client verification.
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</p>
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<p>
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If you mix things, Apache httpd will detect it and return a special
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response code, 421 Misdirected Request, to the client.
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</p>
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<h3><a name="envvars" id="envvars">Environment Variables</a></h3>
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<p>
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This module can be configured to provide HTTP/2 related information
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as additional environment variables to the SSI and CGI namespace, as well
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as in custom log configurations (see <code>%{VAR_NAME}e</code>).
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||
</p>
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<table class="bordered">
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<tr>
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<th><a name="table3">Variable Name:</a></th>
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<th>Value Type:</th>
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<th>Description:</th>
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</tr>
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<tr><td><code>HTTP2</code></td><td>flag</td><td>HTTP/2 is being used.</td></tr>
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<tr><td><code>H2PUSH</code></td><td>flag</td><td>HTTP/2 Server Push is enabled for this connection and also supported by the client.</td></tr>
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<tr><td><code>H2_PUSH</code></td><td>flag</td><td>alternate name for <code>H2PUSH</code></td></tr>
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<tr><td><code>H2_PUSHED</code></td><td>string</td><td>empty or <code>PUSHED</code> for a request being pushed by the server.</td></tr>
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<tr><td><code>H2_PUSHED_ON</code></td><td>number</td><td>HTTP/2 stream number that triggered the push of this request.</td></tr>
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<tr><td><code>H2_STREAM_ID</code></td><td>number</td><td>HTTP/2 stream number of this request.</td></tr>
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<tr><td><code>H2_STREAM_TAG</code></td><td>string</td><td>HTTP/2 process unique stream identifier, consisting of connection id and stream id separated by <code>-</code>.</td></tr>
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||
</table>
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||
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||
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||
</div>
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||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="H2CopyFiles" id="H2CopyFiles">H2CopyFiles</a> <a name="h2copyfiles" id="h2copyfiles">Directive</a> <a title="Permanent link" href="#h2copyfiles" class="permalink">¶</a></h2>
|
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<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine file handling in responses</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2CopyFiles on|off</code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2CopyFiles off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
|
||
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.24 and later.</td></tr>
|
||
</table>
|
||
<p>
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||
This directive influences how file content is handled in
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responses. When <code>off</code>, which is the default, file handles
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||
are passed from the requestion processing down to the main
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||
connection, using the usual Apache setaside handling for
|
||
managing the lifetime of the file.
|
||
</p>
|
||
<p>
|
||
When set to <code>on</code>, file content is copied while the
|
||
request is still being processed and the buffered data is passed
|
||
on to the main connection. This is better if a third party
|
||
module is injecting files with different lifetimes into the response.
|
||
</p>
|
||
<p>
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||
An example for such a module is <code>mod_wsgi</code> that may place
|
||
Python file handles into the response. Those files get close down when
|
||
Python thinks processing has finished. That may be well before
|
||
<code class="module"><a href="../mod/mod_http2.html">mod_http2</a></code> is done with them.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2Direct" id="H2Direct">H2Direct</a> <a name="h2direct" id="h2direct">Directive</a> <a title="Permanent link" href="#h2direct" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>H2 Direct Protocol Switch</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2Direct on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2Direct on for h2c, off for h2 protocol</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive toggles the usage of the HTTP/2 Direct Mode. This
|
||
should be used inside a
|
||
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>
|
||
section to enable direct HTTP/2 communication for that virtual host.
|
||
</p>
|
||
<p>
|
||
Direct communication means that if the first bytes received by the
|
||
server on a connection match the HTTP/2 preamble, the HTTP/2
|
||
protocol is switched to immediately without further negotiation.
|
||
This mode is defined in RFC 7540 for the cleartext (h2c) case. Its
|
||
use on TLS connections not mandated by the standard.
|
||
</p>
|
||
<p>
|
||
When a server/vhost does not have h2 or h2c enabled via
|
||
<code class="directive"><a href="../mod/core.html#protocols">Protocols</a></code>,
|
||
the connection is never inspected for a HTTP/2 preamble.
|
||
<code class="directive">H2Direct</code>
|
||
does not matter then. This is important for connections that
|
||
use protocols where an initial read might hang indefinitely, such
|
||
as NNTP.
|
||
</p>
|
||
<p>
|
||
For clients that have out-of-band knowledge about a server
|
||
supporting h2c, direct HTTP/2 saves the client from having to
|
||
perform an HTTP/1.1 upgrade, resulting in better performance
|
||
and avoiding the Upgrade restrictions on request bodies.
|
||
</p>
|
||
<p>
|
||
This makes direct h2c attractive for server to server communication
|
||
as well, when the connection can be trusted or is secured by other means.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2Direct on</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2EarlyHint" id="H2EarlyHint">H2EarlyHint</a> <a name="h2earlyhint" id="h2earlyhint">Directive</a> <a title="Permanent link" href="#h2earlyhint" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Add a response header to be picked up in 103 Early Hints</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2EarlyHint <em>name</em> <em>value</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.5.1 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
<code class="directive">H2EarlyHint</code> allows adding a response
|
||
header before the real request processing is started. Such headers
|
||
are picked up for "103 Early Hints" intermediate responses. The main
|
||
purpose is to send "preload" information to client browsers.
|
||
</p><p>
|
||
<em>name</em> and <em>value</em> must be valid HTTP header fields
|
||
or will lead to failed responses. <code class="directive">H2EarlyHints</code>
|
||
must still be enabled to allow 103 intermediate responses to be sent.
|
||
This directive can be repeated several times and header fields of the
|
||
same names add.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2EarlyHint Link "</my.css>;rel=preload;as=style"</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2EarlyHints" id="H2EarlyHints">H2EarlyHints</a> <a name="h2earlyhints" id="h2earlyhints">Directive</a> <a title="Permanent link" href="#h2earlyhints" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine sending of 103 status codes</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2EarlyHints on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2EarlyHints off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.24 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
This setting controls if HTTP status 103 interim responses are
|
||
forwarded to the client or not. By default, this is currently
|
||
not the case since a range of clients still have trouble with
|
||
unexpected interim responses.
|
||
</p>
|
||
<p>
|
||
When set to <code>on</code>, PUSH resources announced with
|
||
<code class="directive"><a href="#h2pushresource">H2PushResource</a></code> will
|
||
trigger an interim 103 response
|
||
before the final response. The 103 response will carry <code>Link</code>
|
||
headers that advise the <code>preload</code> of such resources.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2MaxDataFrameLen" id="H2MaxDataFrameLen">H2MaxDataFrameLen</a> <a name="h2maxdataframelen" id="h2maxdataframelen">Directive</a> <a title="Permanent link" href="#h2maxdataframelen" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum bytes inside a single HTTP/2 DATA frame</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2MaxDataFrameLen <em>n</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2MaxDataFrameLen 0</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.5.1 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
<code class="directive">H2MaxDataFrameLen</code> limits the maximum
|
||
amount of response body bytes placed into a single HTTP/2 DATA
|
||
frame. Setting this to 0 places no limit (but the max size
|
||
allowed by the protocol is observed).
|
||
</p><p>
|
||
The module, by default, tries to use the maximum size possible,
|
||
which is somewhat around 16KB. This sets the maximum. When less
|
||
response data is available, smaller frames will be sent.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2MaxSessionStreams" id="H2MaxSessionStreams">H2MaxSessionStreams</a> <a name="h2maxsessionstreams" id="h2maxsessionstreams">Directive</a> <a title="Permanent link" href="#h2maxsessionstreams" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of active streams per HTTP/2 session.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2MaxSessionStreams <em>n</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2MaxSessionStreams 100</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the maximum number of active streams per HTTP/2 session (e.g. connection)
|
||
that the server allows. A stream is active if it is not <code>idle</code> or
|
||
<code>closed</code> according to RFC 7540.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2MaxSessionStreams 20</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2MaxWorkerIdleSeconds" id="H2MaxWorkerIdleSeconds">H2MaxWorkerIdleSeconds</a> <a name="h2maxworkeridleseconds" id="h2maxworkeridleseconds">Directive</a> <a title="Permanent link" href="#h2maxworkeridleseconds" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of seconds h2 workers remain idle until shut down.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2MaxWorkerIdleSeconds <em>n</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2MaxWorkerIdleSeconds 600</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the maximum number of seconds a h2 worker may
|
||
idle until it shuts itself down. This only happens while the number of
|
||
h2 workers exceeds <code class="directive"><a href="#h2minworkers">H2MinWorkers</a></code>.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2MaxWorkerIdleSeconds 20</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2MaxWorkers" id="H2MaxWorkers">H2MaxWorkers</a> <a name="h2maxworkers" id="h2maxworkers">Directive</a> <a title="Permanent link" href="#h2maxworkers" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of worker threads to use per child process.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2MaxWorkers <em>n</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the maximum number of worker threads to spawn
|
||
per child process for HTTP/2 processing. If this directive is not used,
|
||
<code class="module"><a href="../mod/mod_http2.html">mod_http2</a></code> will chose a value suitable for the <code>mpm</code>
|
||
module loaded.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2MaxWorkers 20</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2MinWorkers" id="H2MinWorkers">H2MinWorkers</a> <a name="h2minworkers" id="h2minworkers">Directive</a> <a title="Permanent link" href="#h2minworkers" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimal number of worker threads to use per child process.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2MinWorkers <em>n</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the minimum number of worker threads to spawn
|
||
per child process for HTTP/2 processing. If this directive is not used,
|
||
<code class="module"><a href="../mod/mod_http2.html">mod_http2</a></code> will chose a value suitable for the <code>mpm</code>
|
||
module loaded.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2MinWorkers 10</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2ModernTLSOnly" id="H2ModernTLSOnly">H2ModernTLSOnly</a> <a name="h2moderntlsonly" id="h2moderntlsonly">Directive</a> <a title="Permanent link" href="#h2moderntlsonly" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Require HTTP/2 connections to be "modern TLS" only</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2ModernTLSOnly on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2ModernTLSOnly on</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.18 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive toggles the security checks on HTTP/2 connections
|
||
in TLS mode (https:). This can be used server wide or for specific
|
||
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>s.
|
||
</p>
|
||
<p>
|
||
The security checks require that the TSL protocol is at least
|
||
TLSv1.2 and that none of the ciphers listed in RFC 7540, Appendix A
|
||
is used. These checks will be extended once new security requirements
|
||
come into place.
|
||
</p>
|
||
<p>
|
||
The name stems from the
|
||
<a href="https://wiki.mozilla.org/Security/Server_Side_TLS">Security/Server Side TLS</a>
|
||
definitions at mozilla where "modern compatibility" is defined. Mozilla Firefox and
|
||
other browsers require modern compatibility for HTTP/2 connections. As everything
|
||
in OpSec, this is a moving target and can be expected to evolve in the future.
|
||
</p>
|
||
<p>
|
||
One purpose of having these checks in <code class="module"><a href="../mod/mod_http2.html">mod_http2</a></code> is to enforce this
|
||
security level for all connections, not only those from browsers. The other
|
||
purpose is to prevent the negotiation of HTTP/2 as a protocol should
|
||
the requirements not be met.
|
||
</p>
|
||
<p>
|
||
Ultimately, the security of the TLS connection is determined by the
|
||
server configuration directives for <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code>.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2ModernTLSOnly off</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2OutputBuffering" id="H2OutputBuffering">H2OutputBuffering</a> <a name="h2outputbuffering" id="h2outputbuffering">Directive</a> <a title="Permanent link" href="#h2outputbuffering" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine buffering behaviour of output</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2OutputBuffering on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2OutputBuffering on</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.48 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
The directive <code class="directive">H2OutputBuffering</code> controls the buffering of stream output.
|
||
The default is on, which is the behaviour of previous versions. When off, all
|
||
bytes are made available immediately to the main connection for sending them
|
||
out to the client. This fixes interop issues with certain flavours of gRPC.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2Padding" id="H2Padding">H2Padding</a> <a name="h2padding" id="h2padding">Directive</a> <a title="Permanent link" href="#h2padding" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine the range of padding bytes added to payload frames</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2Padding <em>numbits</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2Padding 0</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.39 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
With the default 0, no padding bytes are added to any payload
|
||
frames, e.g. HEADERS, DATA and PUSH_PROMISE. This is the behaviour
|
||
of previous versions. It means that under certain conditions, an
|
||
observer of network traffic can see the length of those frames
|
||
in the TLS stream.
|
||
</p>
|
||
<p>
|
||
When configuring numbits of 1-8, a random number in range
|
||
[0, 2^numbits[ are added to each frame. The random value is chosen
|
||
independently for each frame that the module sends back to the client.
|
||
</p>
|
||
<p>
|
||
While more padding bytes give better message length obfuscation, they
|
||
are also additional traffic. The optimal number therefore depends on
|
||
the kind of web traffic the server carries.
|
||
</p>
|
||
<p>
|
||
The default of 0, e.g. no padding, was chosen for maximum backward
|
||
compatibility. There might be deployments where padding bytes are
|
||
unwanted or do harm. The most likely cause would be a client that
|
||
has a faults implementation.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2ProxyRequests" id="H2ProxyRequests">H2ProxyRequests</a> <a name="h2proxyrequests" id="h2proxyrequests">Directive</a> <a title="Permanent link" href="#h2proxyrequests" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>En-/Disable forward proxy requests via HTTP/2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2ProxyRequests on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2ProxyRequests off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.5.1 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
Use <code class="directive">H2ProxyRequests</code> to enable or disable
|
||
handling of HTTP/2 requests in a forward proxy configuration.
|
||
</p><p>
|
||
Similar to <code class="directive"><a href="../mod/proxy.html#proxyrequests">ProxyRequests</a></code>, this
|
||
triggers the needed treatment of requests when HTTP/2 is enabled
|
||
in a forward proxy configuration. Both directive should be enabled.
|
||
</p><p>
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2Push" id="H2Push">H2Push</a> <a name="h2push" id="h2push">Directive</a> <a title="Permanent link" href="#h2push" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>H2 Server Push Switch</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2Push on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2Push on</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.18 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive toggles the usage of the HTTP/2 server push
|
||
protocol feature.
|
||
</p>
|
||
<p>
|
||
The HTTP/2 protocol allows the server to push other resources to
|
||
a client when it asked for a particular one. This is helpful
|
||
if those resources are connected in some way and the client can
|
||
be expected to ask for it anyway. The pushing then saves the
|
||
time it takes the client to ask for the resources itself. On the
|
||
other hand, pushing resources the client never needs or already
|
||
has is a waste of bandwidth.
|
||
</p>
|
||
<p>
|
||
Server pushes are detected by inspecting the <code>Link</code> headers of
|
||
responses (see https://tools.ietf.org/html/rfc5988 for the
|
||
specification). When a link thus specified has the <code>rel=preload</code>
|
||
attribute, it is treated as a resource to be pushed.
|
||
</p>
|
||
<p>
|
||
Link headers in responses are either set by the application or
|
||
can be configured via <code class="directive"><a href="#h2pushresource">H2PushResource</a></code> or
|
||
using <code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code> as:
|
||
</p>
|
||
<div class="example"><h3>mod_headers example</h3><pre class="prettyprint lang-config"><Location /index.html>
|
||
Header add Link "</css/site.css>;rel=preload"
|
||
Header add Link "</images/logo.jpg>;rel=preload"
|
||
</Location></pre>
|
||
</div>
|
||
<p>
|
||
As the example shows, there can be several link headers added
|
||
to a response, resulting in several pushes being triggered. There
|
||
are no checks in the module to avoid pushing the same resource
|
||
twice or more to one client. Use with care.
|
||
</p>
|
||
<p>
|
||
HTTP/2 server pushes are enabled by default. On a server or virtual host,
|
||
you may enable/disable this feature for any connection to the host. In addition,
|
||
you may disable PUSH for a set of resources in a Directory/Location. This controls
|
||
which resources may cause a PUSH, not which resources may be sent via PUSH.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2Push off</pre>
|
||
</div>
|
||
<p>
|
||
Last but not least, pushes happen only when the client signals
|
||
its willingness to accept those. Most browsers do, some, like Safari 9,
|
||
do not. Also, pushes also only happen for resources from the same
|
||
<em>authority</em> as the original response is for.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2PushDiarySize" id="H2PushDiarySize">H2PushDiarySize</a> <a name="h2pushdiarysize" id="h2pushdiarysize">Directive</a> <a title="Permanent link" href="#h2pushdiarysize" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>H2 Server Push Diary Size</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2PushDiarySize <em>n</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2PushDiarySize 256</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.19 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive toggles the maximum number of HTTP/2 server pushes
|
||
that are remembered per HTTP/2 connection. This can be used inside the
|
||
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>
|
||
section to influence the number for all connections to that virtual host.
|
||
</p>
|
||
<p>
|
||
The push diary records a digest of pushed
|
||
resources (their URL) to avoid duplicate pushes on the same connection.
|
||
These value are not persisted, so clients opening a new connection
|
||
will experience known pushes again.
|
||
</p>
|
||
<p>
|
||
If the maximum size is reached, newer entries replace the oldest
|
||
ones. A diary entry uses 8 bytes, letting a
|
||
default diary with 256 entries consume around 2 KB of memory.
|
||
</p>
|
||
<p>
|
||
A size of 0 will effectively disable the push diary.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2PushPriority" id="H2PushPriority">H2PushPriority</a> <a name="h2pushpriority" id="h2pushpriority">Directive</a> <a title="Permanent link" href="#h2pushpriority" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>H2 Server Push Priority</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2PushPriority <em>mime-type</em> [after|before|interleaved] [<em>weight</em>]</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2PushPriority * After 16</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.18 and later. For having an
|
||
effect, a nghttp2 library version 1.5.0 or newer is necessary.</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive defines the priority handling of pushed responses
|
||
based on the content-type of the response. This is usually defined
|
||
per server config, but may also appear in a virtual host.
|
||
</p>
|
||
<p>
|
||
HTTP/2 server pushes are always related to a client request. Each
|
||
such request/response pairs, or <em>streams</em> have a dependency
|
||
and a weight, together defining the <em>priority</em> of a stream.
|
||
</p>
|
||
<p>
|
||
When a stream <em>depends</em> on another, say X depends on Y,
|
||
then Y gets all bandwidth before X gets any. Note that this
|
||
does not mean that Y will block X. If Y has no data to send,
|
||
all bandwidth allocated to Y can be used by X.
|
||
</p>
|
||
<p>
|
||
When a stream has more than one dependent, say X1 and X2 both
|
||
depend on Y, the <em>weight</em> determines the bandwidth
|
||
allocation. If X1 and X2 have the same weight, they both get
|
||
half of the available bandwidth. If the weight of X1 is twice
|
||
as large as that for X2, X1 gets twice the bandwidth of X2.
|
||
</p>
|
||
<p>
|
||
Ultimately, every stream depends on the <em>root</em> stream which
|
||
gets all the bandwidth available, but never sends anything. So all
|
||
its bandwidth is distributed by weight among its children. Which
|
||
either have data to send or distribute the bandwidth to their
|
||
own children. And so on. If none of the children have data
|
||
to send, that bandwidth get distributed somewhere else according
|
||
to the same rules.
|
||
</p>
|
||
<p>
|
||
The purpose of this priority system is to always make use of
|
||
available bandwidth while allowing precedence and weight
|
||
to be given to specific streams. Since, normally, all streams
|
||
are initiated by the client, it is also the one that sets
|
||
these priorities.
|
||
</p>
|
||
<p>
|
||
Only when such a stream results in a PUSH, gets the server to
|
||
decide what the <em>initial</em> priority of such a pushed
|
||
stream is. In the examples below, X is the client stream. It
|
||
depends on Y and the server decides to PUSH streams P1 and P2
|
||
onto X.
|
||
</p>
|
||
<p>
|
||
The default priority rule is:
|
||
</p>
|
||
<div class="example"><h3>Default Priority Rule</h3><pre class="prettyprint lang-config">H2PushPriority * After 16</pre>
|
||
</div>
|
||
<p>
|
||
which reads as 'Send a pushed stream of any content-type
|
||
depending on the client stream with weight 16'. And so P1
|
||
and P2 will be send after X and, as they have equal weight,
|
||
share bandwidth equally among themselves.
|
||
</p>
|
||
<div class="example"><h3>Interleaved Priority Rule</h3><pre class="prettyprint lang-config">H2PushPriority text/css Interleaved 256</pre>
|
||
</div>
|
||
<p>
|
||
which reads as 'Send any CSS resource on the same dependency and
|
||
weight as the client stream'. If P1 has content-type 'text/css',
|
||
it will depend on Y (as does X) and its effective weight will be
|
||
calculated as <code>P1ew = Xw * (P1w / 256)</code>. With P1w being
|
||
256, this will make the effective weight the same as the weight
|
||
of X. If both X and P1 have data to send, bandwidth will be allocated
|
||
to both equally.
|
||
</p>
|
||
<p>
|
||
With Pw specified as 512, a pushed, interleaved stream would
|
||
get double the weight of X. With 128 only half as much. Note that
|
||
effective weights are always capped at 256.
|
||
</p>
|
||
<div class="example"><h3>Before Priority Rule</h3><pre class="prettyprint lang-config">H2PushPriority application/json Before</pre>
|
||
</div>
|
||
<p>
|
||
This says that any pushed stream of content type 'application/json'
|
||
should be send out <em>before</em> X. This makes P1 dependent
|
||
on Y and X dependent on P1. So, X will be stalled as long as
|
||
P1 has data to send. The effective weight is inherited from the
|
||
client stream. Specifying a weight is not allowed.
|
||
</p>
|
||
<p>
|
||
Be aware that the effect of priority specifications is limited
|
||
by the available server resources. If a server does not have
|
||
workers available for pushed streams, the data for the stream
|
||
may only ever arrive when other streams have been finished.
|
||
</p>
|
||
<p>
|
||
Last, but not least, there are some specifics of the syntax
|
||
to be used in this directive:
|
||
</p>
|
||
<ol>
|
||
<li>'*' is the only special content-type that matches all others.
|
||
'image/*' will not work.</li>
|
||
<li>The default dependency is 'After'. </li>
|
||
<li>There are also default weights: for 'After' it is 16, 'interleaved' is 256.
|
||
</li>
|
||
</ol>
|
||
<div class="example"><h3>Shorter Priority Rules</h3><pre class="prettyprint lang-config">H2PushPriority application/json 32 # an After rule
|
||
H2PushPriority image/jpeg before # weight inherited
|
||
H2PushPriority text/css interleaved # weight 256 default</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2PushResource" id="H2PushResource">H2PushResource</a> <a name="h2pushresource" id="h2pushresource">Directive</a> <a title="Permanent link" href="#h2pushresource" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Declares resources for early pushing to the client</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2PushResource [add] <em>path</em> [critical]</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
|
||
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.24 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
When added to a directory/location HTTP/2 PUSHes will be attempted
|
||
for all paths added via this directive. This directive can be used
|
||
several times for the same location.
|
||
</p>
|
||
<p>
|
||
This directive pushes resources much earlier than adding
|
||
<code>Link</code> headers via <code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code>.
|
||
<code class="module"><a href="../mod/mod_http2.html">mod_http2</a></code> announces these resources in a
|
||
<code>103 Early Hints</code> interim response to the client.
|
||
That means that clients not supporting PUSH will still get
|
||
early preload hints.
|
||
</p>
|
||
<p>
|
||
In contrast to setting <code>Link</code> response headers
|
||
via <code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code>, this directive will only
|
||
take effect on HTTP/2 connections.
|
||
</p>
|
||
<p>
|
||
By adding <code>critical</code> to such a resource, the server
|
||
will give processing it more preference and send its data, once
|
||
available, before the data from the main request.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2SerializeHeaders" id="H2SerializeHeaders">H2SerializeHeaders</a> <a name="h2serializeheaders" id="h2serializeheaders">Directive</a> <a title="Permanent link" href="#h2serializeheaders" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Serialize Request/Response Processing Switch</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2SerializeHeaders on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2SerializeHeaders off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive toggles if HTTP/2 requests shall be serialized in
|
||
HTTP/1.1 format for processing by <code>httpd</code> core or if
|
||
received binary data shall be passed into the <code>request_rec</code>s
|
||
directly.
|
||
</p>
|
||
<p>
|
||
Serialization will lower performance, but gives more backward
|
||
compatibility in case custom filters/hooks need it.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2SerializeHeaders on</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2StreamMaxMemSize" id="H2StreamMaxMemSize">H2StreamMaxMemSize</a> <a name="h2streammaxmemsize" id="h2streammaxmemsize">Directive</a> <a title="Permanent link" href="#h2streammaxmemsize" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of output data buffered per stream.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2StreamMaxMemSize <em>bytes</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2StreamMaxMemSize 65536</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the maximum number of outgoing data bytes buffered in memory
|
||
for an active streams. This memory is not allocated per stream as such. Allocations
|
||
are counted against this limit when they are about to be done. Stream processing
|
||
freezes when the limit has been reached and will only continue when buffered data
|
||
has been sent out to the client.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2StreamMaxMemSize 128000</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2StreamTimeout" id="H2StreamTimeout">H2StreamTimeout</a> <a name="h2streamtimeout" id="h2streamtimeout">Directive</a> <a title="Permanent link" href="#h2streamtimeout" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum time waiting when sending/receiving data to stream processing</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2StreamTimeout <var>time-interval</var>[s]</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Value of <code class="directive"><a href="../mod/core.html#timeout">Timeout</a></code></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.5.1 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
<code class="directive">H2StreamTimeout</code> specifies the maximum time that
|
||
a stream being processed will wait for its data to be sent/received.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2TLSCoolDownSecs" id="H2TLSCoolDownSecs">H2TLSCoolDownSecs</a> <a name="h2tlscooldownsecs" id="h2tlscooldownsecs">Directive</a> <a title="Permanent link" href="#h2tlscooldownsecs" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure the number of seconds of idle time on TLS before shrinking writes</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2TLSCoolDownSecs <em>seconds</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2TLSCoolDownSecs 1</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.18 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the number of seconds of idle time on a TLS
|
||
connection before the TLS write size falls back to small (~1300 bytes)
|
||
length.
|
||
This can be used server wide or for specific
|
||
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>s.
|
||
</p>
|
||
<p>
|
||
See <code class="directive"><a href="#h2tlswarmupsize">H2TLSWarmUpSize</a></code> for a
|
||
description of TLS warmup. <code class="directive">H2TLSCoolDownSecs</code> reflects the fact
|
||
that connections may deteriorate over time (and TCP flow adjusts)
|
||
for idle connections as well. It is beneficial to overall performance
|
||
to fall back to the pre-warmup phase after a number of seconds that
|
||
no data has been sent.
|
||
</p>
|
||
<p>
|
||
In deployments where connections can be considered reliable, this
|
||
timer can be disabled by setting it to 0.
|
||
</p>
|
||
<p>
|
||
The following example sets the seconds to zero, effectively disabling
|
||
any cool down. Warmed up TLS connections stay on maximum record
|
||
size.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2TLSCoolDownSecs 0</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2TLSWarmUpSize" id="H2TLSWarmUpSize">H2TLSWarmUpSize</a> <a name="h2tlswarmupsize" id="h2tlswarmupsize">Directive</a> <a title="Permanent link" href="#h2tlswarmupsize" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure the number of bytes on TLS connection before doing max writes</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2TLSWarmUpSize <em>amount</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2TLSWarmUpSize 1048576</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.18 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the number of bytes to be sent in small
|
||
TLS records (~1300 bytes) until doing maximum sized writes (16k)
|
||
on https: HTTP/2 connections.
|
||
This can be used server wide or for specific
|
||
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>s.
|
||
</p>
|
||
<p>
|
||
Measurements by <a href="https://www.igvita.com">google performance
|
||
labs</a> show that best performance on TLS connections is reached,
|
||
if initial record sizes stay below the MTU level, to allow a
|
||
complete record to fit into an IP packet.
|
||
</p>
|
||
<p>
|
||
While TCP adjust its flow-control and window sizes, longer TLS
|
||
records can get stuck in queues or get lost and need retransmission.
|
||
This is of course true for all packets. TLS however needs the
|
||
whole record in order to decrypt it. Any missing bytes at the end
|
||
will stall usage of the received ones.
|
||
</p>
|
||
<p>
|
||
After a sufficient number of bytes have been send successfully,
|
||
the TCP state of the connection is stable and maximum TLS record
|
||
sizes (16 KB) can be used for optimal performance.
|
||
</p>
|
||
<p>
|
||
In deployments where servers are reached locally or over reliable
|
||
connections only, the value might be decreased with 0 disabling
|
||
any warmup phase altogether.
|
||
</p>
|
||
<p>
|
||
The following example sets the size to zero, effectively disabling
|
||
any warmup phase.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2TLSWarmUpSize 0</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2Upgrade" id="H2Upgrade">H2Upgrade</a> <a name="h2upgrade" id="h2upgrade">Directive</a> <a title="Permanent link" href="#h2upgrade" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>H2 Upgrade Protocol Switch</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2Upgrade on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2Upgrade on for h2c, off for h2 protocol</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive toggles the usage of the HTTP/1.1 Upgrade method
|
||
for switching to HTTP/2. This
|
||
should be used inside a
|
||
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>
|
||
section to enable Upgrades to HTTP/2 for that virtual host.
|
||
</p>
|
||
<p>
|
||
This method of switching protocols is defined in HTTP/1.1 and
|
||
uses the "Upgrade" header (thus the name) to announce willingness
|
||
to use another protocol. This may happen on any request of a
|
||
HTTP/1.1 connection.
|
||
</p>
|
||
<p>
|
||
This method of protocol switching is enabled by default on cleartext
|
||
(potential h2c) connections and disabled on TLS (potential h2),
|
||
as mandated by RFC 7540.
|
||
</p>
|
||
<p>
|
||
Please be aware that Upgrades are only accepted for requests
|
||
that carry no body. POSTs and PUTs with content will never
|
||
trigger an upgrade to HTTP/2.
|
||
See <code class="directive"><a href="#h2direct">H2Direct</a></code> for an
|
||
alternative to Upgrade.
|
||
</p>
|
||
<p>
|
||
This mode only has an effect when h2 or h2c is enabled via
|
||
the <code class="directive"><a href="../mod/core.html#protocols">Protocols</a></code>.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2Upgrade on</pre>
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2WebSockets" id="H2WebSockets">H2WebSockets</a> <a name="h2websockets" id="h2websockets">Directive</a> <a title="Permanent link" href="#h2websockets" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>En-/Disable WebSockets via HTTP/2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2WebSockets on|off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2WebSockets off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.5.1 and later.</td></tr>
|
||
</table>
|
||
<p>
|
||
Use <code class="directive">H2WebSockets</code> to enable or disable
|
||
bootstrapping of WebSockets via the HTTP/2 protocol. This
|
||
protocol extension is defined in RFC 8441.
|
||
</p><p>
|
||
Such requests come as a CONNECT with an extra ':protocol'
|
||
header. Such requests are transformed inside the module to
|
||
their HTTP/1.1 equivalents before passing it to internal
|
||
processing.
|
||
</p><p>
|
||
This means that HTTP/2 WebSockets can be used for a
|
||
<code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code> with
|
||
'upgrade=websocket' parameter without further changes.
|
||
</p><p>
|
||
For (3rd party) modules that handle WebSockets directly in the
|
||
server, the protocol bootstrapping itself will also work. However
|
||
the transfer of data does require extra support in case of HTTP/2.
|
||
The negotiated WebSocket will not be able to use the client connection
|
||
socket for polling IO related events.
|
||
</p><p>
|
||
Because enabling this feature might break backward compatibility
|
||
for such 3rd party modules, it is not enabled by default.
|
||
</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="H2WindowSize" id="H2WindowSize">H2WindowSize</a> <a name="h2windowsize" id="h2windowsize">Directive</a> <a title="Permanent link" href="#h2windowsize" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Size of Stream Window for upstream data.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2WindowSize <em>bytes</em></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>H2WindowSize 65535</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_http2</td></tr>
|
||
</table>
|
||
<p>
|
||
This directive sets the size of the window that is used for flow control
|
||
from client to server and limits the amount of data the server has to buffer.
|
||
The client will stop sending on a stream once the limit has been reached until
|
||
the server announces more available space (as it has processed some of the data).
|
||
</p><p>
|
||
This limit affects only request bodies, not its meta data such as headers. Also,
|
||
it has no effect on response bodies as the window size for those are managed
|
||
by the clients.
|
||
</p>
|
||
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">H2WindowSize 128000</pre>
|
||
</div>
|
||
|
||
</div>
|
||
</div>
|
||
<div class="bottomlang">
|
||
<p><span>Available Languages: </span><a href="../en/mod/mod_http2.html" title="English"> en </a> |
|
||
<a href="../fr/mod/mod_http2.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p>
|
||
</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Libera.chat, or sent to our <a href="https://httpd.apache.org/lists.html">mailing lists</a>.</div>
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