mod_cache: overriding Cache-Control and Vary

[Graham Leggett]

Hi all,

One of the missing things that mod_cache can't do that other caches  
can is to be able to override the Cache-Control and Vary headers, so  
that the cache can be targeted for custom behaviour.

The classic use case is when you insert request headers into your  
server stack, which you want to vary on. The Vary header in this case  
would make no sense to the internet at large, or the Vary header for  
the benefit of the internet may be different to the Vary header for  
the benefit of mod_cache.

What I propose are some simple per-directory directives, allowing you  
to optionally override the names of Cache-Control, Pragma, and Vary  
headers for outgoing requests, for example X-Cache-Control, X-Pragma  
or X-Vary.

Regards,
Graham
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