docs/manual/mod/mod_proxy_scgi.xml

<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<!-- $LastChangedRevision$ -->

<!--
 Licensed to the Apache Software Foundation (ASF) under one or more
 contributor license agreements.  See the NOTICE file distributed with
 this work for additional information regarding copyright ownership.
 The ASF licenses this file to You under the Apache License, Version 2.0
 (the "License"); you may not use this file except in compliance with
 the License.  You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
-->

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

<name>mod_proxy_scgi</name>
<description>SCGI gateway module for <module>mod_proxy</module></description>
<status>Extension</status>
<sourcefile>mod_proxy_scgi.c</sourcefile>
<identifier>proxy_scgi_module</identifier>

<summary>
    <p>This module <em>requires</em> the service of <module
    >mod_proxy</module>. It provides support for the
    <a href="http://python.ca/scgi/protocol.txt">SCGI protocol, version
    1</a>.</p>

    <p>Thus, in order to get the ability of handling the SCGI protocol,
    <module>mod_proxy</module> and <module>mod_proxy_scgi</module> have to
    be present in the server.</p>

    <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_proxy</module></seealso>
<seealso><module>mod_proxy_balancer</module></seealso>

<section id="examples"><title>Examples</title>
    <p>Remember, in order to make the following examples work, you have to
    enable <module>mod_proxy</module> and <module>mod_proxy_scgi</module>.</p>

    <example><title>Simple gateway</title>
    <highlight language="config">
ProxyPass "/scgi-bin/" "scgi://localhost:4000/"
      </highlight>
    </example>

    <p>The balanced gateway needs <module>mod_proxy_balancer</module> and
    at least one load balancer algorithm module, such as
    <module>mod_lbmethod_byrequests</module>, in addition to the proxy
    modules listed above.  <module>mod_lbmethod_byrequests</module> is the
    default, and will be used for this example configuration.</p>

    <example><title>Balanced gateway</title>
    <highlight language="config">
ProxyPass "/scgi-bin/" "balancer://somecluster/"
&lt;Proxy balancer://somecluster&gt;
    BalancerMember scgi://localhost:4000
    BalancerMember scgi://localhost:4001
&lt;/Proxy&gt;
    </highlight>
    </example>
</section>

<section id="env"><title>Environment Variables</title>
    <p>In addition to the configuration directives that control the
    behavior of <module>mod_proxy</module>, an <dfn>environment
    variable</dfn> may also control the SCGI protocol
    provider:</p>
    <dl>
        <dt>proxy-scgi-pathinfo</dt>
        <dd>By default <module>mod_proxy_scgi</module> will neither create
        nor export the <var><glossary ref="pathinfo">PATH_INFO</glossary></var> environment variable. This allows
        the backend SCGI server to correctly determine <var>SCRIPT_NAME</var>
        and <var>Script-URI</var> and be compliant with RFC 3875 section 3.3.
        If instead you need <module>mod_proxy_scgi</module> to generate
        a "best guess" for <var>PATH_INFO</var>, set this env-var.  The
        variable must be set before <directive module="mod_env">SetEnv</directive>
        is effective.  <directive module="mod_setenvif">SetEnvIf</directive> can be
        used instead: <code>SetEnvIf Request_URI . proxy-scgi-pathinfo</code>
        </dd>
    </dl>
</section>

<directivesynopsis>
<name>ProxySCGISendfile</name>
<description>Enable evaluation of <var>X-Sendfile</var> pseudo response
header</description>
<syntax>ProxySCGISendfile On|Off|<var>Headername</var></syntax>
<default>ProxySCGISendfile Off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context></contextlist>

<usage>
    <p>The <directive>ProxySCGISendfile</directive> directive enables the
    SCGI backend to let files be served directly by the gateway. This is useful
    for performance purposes &mdash; httpd can use <code>sendfile</code> or other
    optimizations, which are not possible if the file comes over the backend
    socket.  Additionally, the file contents are not transmitted twice.</p>
    <p>The <directive>ProxySCGISendfile</directive> argument determines the
    gateway behavior:</p>
    <dl>
    <dt><code>Off</code></dt>
    <dd>No special handling takes place.</dd>

    <dt><code>On</code></dt>
    <dd>The gateway looks for a backend response header called
    <code>X-Sendfile</code> and interprets the value as the filename to serve.
    The  header is removed from the final response headers. This is equivalent to
    <code>ProxySCGISendfile X-Sendfile</code>.</dd>

    <dt>anything else</dt>
    <dd>Similar to <code>On</code>, but instead of the hardcoded header name
    <code>X-Sendfile</code>, the argument is used as the header name.</dd>
    </dl>

    <example><title>Example</title>
    <highlight language="config">
# Use the default header (X-Sendfile)
ProxySCGISendfile On

# Use a different header
ProxySCGISendfile X-Send-Static
    </highlight>
    </example>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxySCGIInternalRedirect</name>
<description>Enable or disable internal redirect responses from the
backend</description>
<syntax>ProxySCGIInternalRedirect On|Off|<var>Headername</var></syntax>
<default>ProxySCGIInternalRedirect On</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context></contextlist>
<compatibility>The <var>Headername</var> feature is available in Apache
httpd 2.4.13 and later.</compatibility>

<usage>
    <p>The <directive>ProxySCGIInternalRedirect</directive> enables the backend
    to internally redirect the gateway to a different URL. This feature
    originates in <module>mod_cgi</module>, which internally redirects the
    response if the response status is <code>OK</code> (<code>200</code>) and
    the response contains a <code>Location</code> (or configured alternate
    header) and its value starts with a slash (<code>/</code>). This value is 
    interpreted as a new local URL that Apache httpd internally redirects to.</p>

    <p><module>mod_proxy_scgi</module> does the same as
    <module>mod_cgi</module> in this regard, except that you can turn off the
    feature or specify the use of a header other than <code>Location</code>.</p>

    <example><title>Example</title>
    <highlight language="config">
    ProxySCGIInternalRedirect Off

# Django and some other frameworks will fully qualify "local URLs"
# set by the application, so an alternate header must be used.
&lt;Location /django-app/&gt;
    ProxySCGIInternalRedirect X-Location
&lt;/Location&gt;
    </highlight>
    </example>
</usage>
</directivesynopsis>

</modulesynopsis>