Apache > HTTP Server > Documentation > Version 2.4 > Modules

Apache Module mod_proxy_scgi

Description:SCGI gateway module for mod_proxy
Module Identifier:proxy_scgi_module
Source File:mod_proxy_scgi.c
Compatibility:Available in version 2.2.14 and later


This module requires the service of mod_proxy. It provides support for the SCGI protocol, version 1.

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


Do not enable proxying until you have secured your server. Open proxy servers are dangerous both to your network and to the Internet at large.



See also



Remember, in order to make the following examples work, you have to enable mod_proxy and mod_proxy_scgi.

Simple gateway

      ProxyPass /scgi-bin/ scgi://localhost:4000/

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

Balanced gateway

ProxyPass /scgi-bin/ balancer://somecluster/
<Proxy balancer://somecluster/>
    BalancerMember scgi://localhost:4000/
    BalancerMember scgi://localhost:4001/

Environment Variables

In addition to the configuration directives that control the behaviour of mod_proxy, there are a number of environment variables that control the SCGI protocol provider:

By default mod_proxy_scgi will neither create nor export the PATH_INFO environment variable. This allows the backend SCGI server to correctly determine SCRIPT_NAME and Script-URI and be compliant with RFC 3875 section 3.3. If instead you need mod_proxy_scgi to generate a "best guess" for PATH_INFO, set this env-var.

ProxySCGIInternalRedirect Directive

Description:Enable or disable internal redirect responses from the backend
Syntax:ProxySCGIInternalRedirect On|Off
Default:ProxySCGIInternalRedirect On
Context:server config, virtual host, directory

The ProxySCGIInternalRedirect enables the backend to internally redirect the gateway to a different URL. This feature origins in mod_cgi, which internally redirects the response, if the response status is OK (200) and the response contains a Location header and its value starts with a slash (/). This value is interpreted as a new local URL the apache internally redirects to.

mod_proxy_scgi does the same as mod_cgi in this regard, except that you can turn off the feature.


    ProxySCGIInternalRedirect Off

ProxySCGISendfile Directive

Description:Enable evaluation of X-Sendfile pseudo response header
Syntax:ProxySCGISendfile On|Off|Headername
Default:ProxySCGISendfile Off
Context:server config, virtual host, directory

The ProxySCGISendfile directive enables the SCGI backend to let files serve directly by the gateway. This is useful performance purposes -- the httpd can use sendfile or other optimizations, which are not possible if the file comes over the backend socket.

The ProxySCGISendfile argument determines the gateway behaviour:

No special handling takes place.
The gateway looks for a backend response header called X-Sendfile and interprets the value as filename to serve. The header is removed from the final response headers. This is equivalent to ProxySCGISendfile X-Sendfile.
anything else
Similar to On, but instead of the hardcoded header name the argument is applied as header name.


    # Use the default header (X-Sendfile)
    ProxySCGISendfile On
    # Use a different header
    ProxySCGISendfile X-Send-Static