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List:       apache-httpd-dev
Subject:    forget quick_handler, make stuff cachable anyways
From:       Brian Degenhardt <bmd () mp3 ! com>
Date:       2002-07-31 21:47:13
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Just wanted to voice my opinion here.  I do a lot of work with caching
proxies and it would be really nice to have apache be intelligent to
how things are cached.  There's two types of changes that would really
help caches and proxies, internal and external to apache:

1) Make apache modules add apropriate headers to inform caches of the
   cacheability of objects.  Does something vary based on cookies? put
   a "Vary: cookie" in the outgoing headers.  Are we using an AAA
   plugin, put "Cache-Control: private" in the headers.  This would
   really make the complex behavoir of apache modules easier to deal
   with for downstream caches.  I think it would be a mistake to use
   apache-specific mechanisms such as looking at the filter stack to
   try to figure out this information.  Let's use HTTP for it.

2) Make mod_cache aware of the stuff set by (1).  This doesn't have to
   be intelligent.  Squid doesn't cache anything with a Vary header in
   it.  Sounds good to me.  Note that moving mod_cache forward in the
   request cycle only satisfies situations where your modules are
   running inside of apache.  If the mod_cache instance is running on
   a separate proxy machine downstream from the machine running the
   AAA plugin, you're screwed unless the correct headers are set and
   read.

Now, I haven't looked at all of the code to make sure that these
things are satisfied.  I know that mod_rewrite does a good job of
setting the Vary header based on rewrite rules but that's the extent
of my knowledge.  I just wanted to get this in everyone's mind as a
valuable goal.  If you guys want, I can audit the existing plugins to
see how they behave along these lines.

cheers

-bmd

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