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| <p class="apache">Apache HTTP Server Version 2.5</p> |
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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> |
| <div id="page-content"> |
| <div id="preamble"><h1>Apache Module mod_http2</h1> |
| <div class="toplang"> |
| <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> |
| <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Support for the HTTP/2 transport layer</td></tr> |
| <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>http2_module</td></tr> |
| <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_http2.c</td></tr> |
| <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.17 and later</td></tr></table> |
| <h3>Summary</h3> |
| |
| <p>This module provides HTTP/2 (<a href="https://tools.ietf.org/html/rfc7540">RFC 7540</a>) |
| support for the Apache HTTP Server.</p> |
| |
| <p>This module relies on <a href="http://nghttp2.org/">libnghttp2</a> |
| to provide the core http/2 engine.</p> |
| |
| <p>You must enable HTTP/2 via <code class="directive"><a href="../mod/core.html#protocols">Protocols</a></code> |
| in order to use the functionality described in this document. The |
| 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: |
| <code>h2</code> (HTTP/2 over TLS) and <code>h2c</code> (HTTP/2 over TCP).</p> |
| |
| <p>Two useful configuration schemes are:</p> |
| |
| <div class="note"><h3>HTTP/2 in a VirtualHost context (TLS only)</h3> |
| <pre class="prettyprint lang-config">Protocols h2 http/1.1</pre> |
| |
| <p>Allows HTTP/2 negotiation (h2) via TLS ALPN in a secure |
| <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>. |
| 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> |
| </div> |
| |
| <div class="note"><h3>HTTP/2 in a Server context (TLS and cleartext)</h3> |
| <pre class="prettyprint lang-config">Protocols h2 h2c http/1.1</pre> |
| |
| <p>Allows HTTP/2 negotiation (h2) via TLS ALPN for secure |
| <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>. Allows |
| HTTP/2 cleartext negotiation (h2c) upgrading from an initial HTTP/1.1 |
| connection or via HTTP/2 preamble checking (Direct mode, see |
| <code class="directive"><a href="#h2direct">H2Direct</a></code>).</p> |
| </div> |
| |
| <p>Refer to the official <a href="https://http2.github.io/faq">HTTP/2 FAQ</a> |
| for any doubt about the protocol.</p> |
| |
| </div> |
| <div id="quickview"><h3>Topics</h3> |
| <ul id="topics"> |
| <li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it works</a></li> |
| </ul><h3 class="directives">Directives</h3> |
| <ul id="toc"> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2copyfiles">H2CopyFiles</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2direct">H2Direct</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2earlyhint">H2EarlyHint</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2earlyhints">H2EarlyHints</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2maxdataframelen">H2MaxDataFrameLen</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2maxsessionstreams">H2MaxSessionStreams</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2maxworkeridleseconds">H2MaxWorkerIdleSeconds</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2maxworkers">H2MaxWorkers</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2minworkers">H2MinWorkers</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2moderntlsonly">H2ModernTLSOnly</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2outputbuffering">H2OutputBuffering</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2padding">H2Padding</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2proxyrequests">H2ProxyRequests</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2push">H2Push</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2pushdiarysize">H2PushDiarySize</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2pushpriority">H2PushPriority</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2pushresource">H2PushResource</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2serializeheaders">H2SerializeHeaders</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2streammaxmemsize">H2StreamMaxMemSize</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2streamtimeout">H2StreamTimeout</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2tlscooldownsecs">H2TLSCoolDownSecs</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2tlswarmupsize">H2TLSWarmUpSize</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2upgrade">H2Upgrade</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2websockets">H2WebSockets</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#h2windowsize">H2WindowSize</a></li> |
| </ul> |
| <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> |
| <ul class="seealso"> |
| <li><a href="#comments_section">Comments</a></li></ul></div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <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> |
| |
| <h3><a name="dimensioning" id="dimensioning">HTTP/2 Dimensioning</a></h3> |
| <p> |
| Enabling HTTP/2 on your Apache Server has impact on the resource |
| consumption and if you have a busy site, you may need to consider |
| carefully the implications. |
| </p> |
| <p> |
| The first noticeable thing after enabling HTTP/2 is that your server |
| processes will start additional threads. The reason for this is that |
| HTTP/2 gives all requests that it receives to its own <em>Worker</em> |
| threads for processing, collects the results and streams them out |
| to the client. |
| </p> |
| <p> |
| In the current implementation, these workers use a separate thread |
| pool from the MPM workers that you might be familiar with. This is |
| just how things are right now and not intended to be like this forever. |
| (It might be forever for the 2.4.x release line, though.) So, HTTP/2 |
| workers, or shorter H2Workers, will not show up in <code class="module"><a href="../mod/mod_status.html">mod_status</a></code>. They |
| are also not counted against directives such as <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code>. However |
| they take <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> |
| as default if you have not configured something |
| else via <code class="directive"><a href="#h2minworkers">H2MinWorkers</a></code> and |
| <code class="directive"><a href="#h2maxworkers">H2MaxWorkers</a></code>. |
| </p> |
| <p> |
| Another thing to watch out for is is memory consumption. Since HTTP/2 |
| keeps more state on the server to manage all the open request, priorities |
| for and dependencies between them, it will always need more memory |
| than HTTP/1.1 processing. There are three directives which steer the |
| memory footprint of a HTTP/2 connection: |
| <code class="directive"><a href="#h2maxsessionstreams">H2MaxSessionStreams</a></code>, |
| <code class="directive"><a href="#h2windowsize">H2WindowSize</a></code> and |
| <code class="directive"><a href="#h2streammaxmemsize">H2StreamMaxMemSize</a></code>. |
| </p> |
| <p> |
| <code class="directive"><a href="#h2maxsessionstreams">H2MaxSessionStreams</a></code> limits the |
| number of parallel requests that a client can make on a HTTP/2 connection. |
| It depends on your site how many you should allow. The default is 100 which |
| is plenty and unless you run into memory problems, I would keep it this |
| way. Most requests that browsers send are GETs without a body, so they |
| use up only a little bit of memory until the actual processing starts. |
| </p> |
| <p> |
| <code class="directive"><a href="#h2windowsize">H2WindowSize</a></code> controls how much |
| the client is allowed to send as body of a request, before it waits |
| for the server to encourage more. Or, the other way around, it is the |
| amount of request body data the server needs to be able to buffer. This |
| is per request. |
| </p> |
| <p> |
| And last, but not least, <code class="directive"><a href="#h2streammaxmemsize">H2StreamMaxMemSize</a></code> |
| controls how much response data shall be buffered. The request sits in |
| a H2Worker thread and is producing data, the HTTP/2 connection tries |
| to send this to the client. If the client does not read fast enough, |
| the connection will buffer this amount of data and then suspend the |
| H2Worker. |
| </p> |
| |
| |
| <h3><a name="misdirected" id="misdirected">Multiple Hosts and Misdirected Requests</a></h3> |
| <p> |
| Many sites use the same TLS certificate for multiple virtual hosts. The |
| certificate either has a wildcard name, such as '*.example.org' or carries |
| several alternate names. Browsers using HTTP/2 will recognize that and reuse |
| an already opened connection for such hosts. |
| </p> |
| <p> |
| While this is great for performance, it comes at a price: such vhosts |
| need more care in their configuration. The problem is that you will have |
| multiple requests for multiple hosts on the same TLS connection. And that |
| makes renegotiation impossible, in face the HTTP/2 standard forbids it. |
| </p> |
| <p> |
| So, if you have several virtual hosts using the same certificate and |
| want to use HTTP/2 for them, you need to make sure that all vhosts have |
| exactly the same SSL configuration. You need the same protocol, |
| ciphers and settings for client verification. |
| </p> |
| <p> |
| If you mix things, Apache httpd will detect it and return a special |
| response code, 421 Misdirected Request, to the client. |
| </p> |
| |
| |
| <h3><a name="envvars" id="envvars">Environment Variables</a></h3> |
| <p> |
| This module can be configured to provide HTTP/2 related information |
| as additional environment variables to the SSI and CGI namespace, as well |
| as in custom log configurations (see <code>%{VAR_NAME}e</code>). |
| </p> |
| |
| <table class="bordered"> |
| |
| <tr> |
| <th><a name="table3">Variable Name:</a></th> |
| <th>Value Type:</th> |
| <th>Description:</th> |
| </tr> |
| <tr><td><code>HTTP2</code></td><td>flag</td><td>HTTP/2 is being used.</td></tr> |
| <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> |
| <tr><td><code>H2_PUSH</code></td><td>flag</td><td>alternate name for <code>H2PUSH</code></td></tr> |
| <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> |
| <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> |
| <tr><td><code>H2_STREAM_ID</code></td><td>number</td><td>HTTP/2 stream number of this request.</td></tr> |
| <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> |
| </table> |
| |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <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> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine file handling in responses</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>H2CopyFiles on|off</code></td></tr> |
| <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> |
| This directive influences how file content is handled in |
| responses. When <code>off</code>, which is the default, file handles |
| are passed from the requestion processing down to the main |
| 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> |
| 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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