I'm trying to configure mod_cache in Apache 2.2.17 to act as a transparent
cache for an application server but I have
some special requirements whose overall purpose is to cache "public" access but
bypass the cache when users are logged
in. I'm setting a cookie "NOCACHE=on" when the user logs in and checking for
that cookie in Apache. For this to work
clients must always revalidate with the cache (to send the cookies).
My requirements are:
* Clients should always revalidate with the cache but NOT the application
server unless a special cookie is set.
* If a page is in the Apache cache the cache should send 304, not the whole
page.
* If user shift-refreshes the browser always revalidate with the application
server.
* I can't use alternate domains, ssl or special paths or query strings for
logged-in users because my application isn't
designed that way.
I'm been experimenting with different headers and cache options but so far I
haven't found a solution that satisfies all
the requirements. Generally when I get one thing to work another breaks eg:
* The HTTP spec solution of using vary: Set-Cookie won't work because the
application sets session cookies and you can't
pick one cookie out of the string.
* Using 'CacheIgnoreCacheControl on' allows the cache to work with no-cache
headers but prevents shift-refresh from
hitting the application server.
* Setting max-age=0 or no-cache in headers with 'CacheIgnoreCacheControl off'
causes the page to not cache in Apache at
all.
* Setting no-store with 'CacheStoreNoStore On' is pretty close but since the
client wont store the page the cache is
sending the whole response body every time (not 304).
My vhost config:
====================
# Expiry and cache-control
# Set expires header
ExpiresActive On
ExpiresDefault "access plus 1 days"
#ExpiresByType text/html "now"
# Check for NOCACHE cookie sent by logged-in users and bypass the cache
SetEnvIf Cookie "NOCACHE" no-cache
Header set Cache-Control "no-cache" env=no-cache
# Force all requests to re-validate so cookies are sent even when the
browser has cached the page
Header append Cache-Control "must-revalidate"
# Don't cache cookie headers
CacheIgnoreHeaders Set-Cookie
# Enable disk cache
CacheEnable disk /
CacheDisable /images
CacheDisable /styles
CacheDisable /scripts
CacheDisable /base
CacheDisable /users
CacheDisable /admin
CacheRoot /var/cache/apache2
# Various attempts to treat this cache differently to downstream caches
#CacheStoreNoStore On
#CacheIgnoreCacheControl on
#CacheIgnoreNoLastMod On
# Forward uncached requests to the application server
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !/[^/:]+\.[^/:]{2,5}$
RewriteRule (.*) /index.cfm$1 [PT,L]
====================
Final thing, the Apache docs seem to use CacheStoreNo*Store* and
CacheStoreNo*Cache* interchangeably. Is this an alias
or a typo? Which is correct?
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