Apache > HTTP Server > Documentation > Version 2.4 > Modules

Apache Module mod_proxy_scgi

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Description:SCGI gateway module for mod_proxy
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 originates 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 that Apache httpd 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 be served directly by the gateway. This is useful for performance purposes — httpd can use sendfile or other optimizations, which are not possible if the file comes over the backend socket. Additionally, the file contents are not transmitted twice.

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 the 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 X-Sendfile, the argument is used as the header name.


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

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