docs/manual/mod/mod_proxy_http2.xml

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<modulesynopsis metafile="mod_proxy_http2.xml.meta">

<name>mod_proxy_http2</name>
<description>HTTP/2 support module for
<module>mod_proxy</module></description>
<status>Experimental</status>
<sourcefile>mod_proxy_http2.c</sourcefile>
<identifier>proxy_http2_module</identifier>
<compatibility>Available in httpd 2.4.19 and later</compatibility>

<summary>
    <p><module>mod_proxy_http2</module>
    supports HTTP/2 only, it does <em>not</em>
    provide any downgrades to HTTP/1.1. This means that the backend
    needs to support HTTP/2 because HTTP/1.1 will not be used instead.</p>

    <p>This module <em>requires</em> the service of <module
    >mod_proxy</module>, so in order to get the ability of
    handling HTTP/2 proxy requests,
    <module>mod_proxy</module> and <module>mod_proxy_http2</module>
    need to be both loaded by the server.</p>

    <p><module>mod_proxy_http2</module> works with incoming fronted requests
    using HTTP/1.1 or HTTP/2. In both cases, requests proxied
    to the same backend are sent over a single TCP connection
    whenever possible (namely when the connection can be re-used).</p>

    <p>Caveat: there will be no attempt to consolidate multiple HTTP/1.1 
    frontend requests (configured to be proxied to the same backend)
    into HTTP/2 streams belonging to the same HTTP/2 request.
    Each HTTP/1.1 frontend request will be proxied to the backend using
    a separate HTTP/2 request (trying to re-use the same TCP connection
    if possible).</p>

    <p>This module relies on <a href="http://nghttp2.org/">libnghttp2</a>
    to provide the core http/2 engine.</p>

    <note type="warning"><title>Warning</title>
        <p>This module is experimental. Its behaviors, directives, and 
        defaults are subject to more change from release to 
        release relative to other standard modules. Users are encouraged to 
        consult the "CHANGES" file for potential updates.</p>
    </note>

    <note type="warning"><title>Warning</title>
      <p>Do not enable proxying until you have <a
      href="mod_proxy.html#access">secured your server</a>. Open proxy
      servers are dangerous both to your network and to the Internet at
      large.</p>
    </note>
</summary>
<seealso><module>mod_http2</module></seealso>
<seealso><module>mod_proxy</module></seealso>
<seealso><module>mod_proxy_connect</module></seealso>

    <section id="examples"><title>Basic Examples</title>

    <p>The examples below demonstrate how to configure HTTP/2 for
    backend connections for a reverse proxy. </p>

    <example><title>HTTP/2 (TLS)</title>
    <highlight language="config">
ProxyPass "/app" "h2://app.example.com"
ProxyPassReverse "/app" "https://app.example.com"
    </highlight>
    </example>

    <example><title>HTTP/2 (cleartext)</title>
    <highlight language="config">
ProxyPass "/app" "h2c://app.example.com"
ProxyPassReverse "/app" "http://app.example.com"
    </highlight>
    </example>

    <note>
      <p>The schemes to configure above in
      <directive>ProxyPassReverse</directive> for reverse proxying
      <code>h2</code> (or <code>h2c</code>) protocols are the usual
      <code>https</code> (resp. <code>http</code>) as expected/used by
      the user agent.</p>
    </note>
    </section> <!-- /examples -->

<section id="notes"><title>Request notes</title>
    <p><module>mod_proxy_http</module> creates the following request notes for
        logging using the <code>%{VARNAME}n</code> format in
        <directive module="mod_log_config">LogFormat</directive> or
        <directive module="core">ErrorLogFormat</directive>:
    </p>
    <dl>
        <dt>proxy-source-port</dt>
        <dd>The local port used for the connection to the backend server.</dd>
        <dt>proxy-status</dt>
        <dd>The HTTP/2 status received from the backend server.</dd>
    </dl>
</section>

<section id="h2push"><title>HTTP/2 PUSH</title>
    <p>The module does not support the HTTP/2 feature PUSH. Backend servers
    that would like to advertise preload resources should send the appropriate 
    <code>Link</code> headers.</p>
    <p>If available, they may do so using the <code>"103 Early Hints"</code> 
    intermediate responses as specified in 
    <rfc>8297</rfc>. This will give
    the best performance. If the client is talking HTTP/2 as well, this may
    then result in a PUSH from Apache to the client or just in forwarding
    the 103 response.</p>
    
</section>

</modulesynopsis>