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<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>
<compatibility>Available in version 2.2.14 and later</compatibility>

<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
    behaviour 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>PATH_INFO</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="env">SetEnv</directive>
        is effective.  <directive module="setenv">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 behaviour:</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 version
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>
