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Apache HTTP Server Version 2.4

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Apache Module mod_proxy_scgi

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

Summary

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.

Warning

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

Topics

• Examples
• Environment Variables

Directives

• ProxySCGIInternalRedirect
• ProxySCGISendfile

Bugfix checklist

• httpd changelog
• Known issues
• Report a bug

See also

• mod_proxy
• mod_proxy_balancer
• Comments

Examples

Remember, in order to make the following examples work, we 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"
</Proxy>

Environment Variables

In addition to the configuration directives that control the behaviour of mod_proxy, an environment variable may also control the SCGI protocol provider:

proxy-scgi-pathinfo

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 we need mod_proxy_scgi to generate a "best guess" for PATH_INFO, set this env-var. The variable must be set before SetEnv is effective. SetEnvIf can be used instead: SetEnvIf Request_URI . proxy-scgi-pathinfo

ProxySCGIInternalRedirect Directive

Description:	Enable or disable internal redirect responses from the backend
Syntax:	ProxySCGIInternalRedirect On|Off|Headername
Default:	ProxySCGIInternalRedirect On
Context:	server config, virtual host, directory
Status:	Extension
Module:	mod_proxy_scgi
Compatibility:	The Headername feature is available in version 2.4.13 and later

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 (or configured alternate 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 we can turn off the feature or specify the use of a header other than Location.

Example

    ProxySCGIInternalRedirect Off

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

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
Status:	Extension
Module:	mod_proxy_scgi

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:

Off

No special handling takes place.

On

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.

Example

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