Chapter 3. URL Mapping
URL mapping, or translation, is the first major stage in request handling. Later stages, such as access controls and content type determination, work with the translated URL.
Initial Environment Setup
The mod_setenvif module is run before URL translation for main and virtual server contexts and after URL translation for directory sections and .htaccess files. At this point, only the values of the request line and of the HTTP request headers are available. mod_setenvif sets environment variables based on these values; the variables are in turn often used to control URL rewriting, authentication, conditional logging, and other conditional behaviors.
There are a number of special environment variables that, if set, modify the response of the server, particularly to cope with buggy clients. mod_proxy defines further special variables related to proxying; these are covered in Chapter 9.
downgrade-1.0Forces the request to be treated as an HTTP/1.0 request
force-gzipForces output compression if the
DEFLATEfilter is activatedforce-no-varyForces any
Varyheaders to be removed from the response (impliesforce-response-1.0)force-response-1.0Forces Apache to respond with an HTTP/1.0 response
gzip-only-text/htmlDisables compression for content types other than
text/htmlif the value is set to 1no-gzipDisables compressed output
nokeepaliveDisables keepalive
prefer-languageIndicates a preferred language that overrides the content negotiation process and takes precedence over the ...