Setting Up Apache as a Forward Proxy with Caching

apache-2.2cachePROXY

I am trying to set up Apache as a forward proxy with caching, but it does not seem to be working correctly. Getting Apache working as a forward proxy was no problem, but no matter what I do it is not caching anything, to disk or memory. I already checked to make sure nothing is conflicting in the mods_enabled directory with mod_cache (ended up commenting it all out) and also I tried moving all of the caching related fields to the configuration file for mod_cache. In addition I set up logging for caching requests, but nothing is being written to those logs. Below is my Apache config, any help would be greatly appreciated!!

<VIRTUALHOST *:8080>
ProxyRequests On
ProxyVia On
#ErrorLog "/var/log/apache2/proxy-error.log"
#CustomLog "/var/log/apache2/proxy-access.log" common
CustomLog "/var/log/apache2/cached-requests.log" common env=cache-hit
CustomLog "/var/log/apache2/uncached-requests.log" common env=cache-miss
CustomLog "/var/log/apache2/revalidated-requests.log" common env=cache-revalidate
CustomLog "/var/log/apache2/invalidated-requests.log" common env=cache-invalidate
LogFormat "%{cache-status}e ..."

        # This path must be the same as the one in /etc/default/apache2
        CacheRoot /var/cache/apache2/mod_disk_cache

        # This will also cache local documents. It usually makes more sense to
        # put this into the configuration for just one virtual host.

        CacheEnable disk /
        #CacheHeader on
        CacheDirLevels 3
        CacheDirLength 5
##<IfModule mod_mem_cache.c>
#        CacheEnable mem /
#        MCacheSize 4096
#        MCacheMaxObjectCount 100
#        MCacheMinObjectSize 1
#        MCacheMaxObjectSize 2048
#</IfModule>


<Proxy *>
Order deny,allow
Deny from all
Allow from x.x.x.x
#IP above hidden for this post

<filesMatch "\.(xml|txt|html|js|css)$">
ExpiresDefault A7200
Header append Cache-Control "proxy-revalidate"
</filesMatch>

</Proxy>
</VIRTUALHOST>

Best Answer

This is an old post, but I found it in hopes of finding my own answers, so I will share what I can, maybe it's useful.

Given what you've said, I would:

  1. Ensure that apache has write access to /var/cache/apache2/mod_disk_cache

  2. Confirm it can even cache something by forcing it to cache everything and checking to see that the cache directory is not empty (full example):

    CacheIgnoreNoLastMod On

    CacheDefaultExpire 7200

  3. If the above doesn't work then I believe the issue is not with mod_cache or mod_disk_cache. Stop here if so, else keep going:

  4. Ensure that the requests to xml|txt|html|js|css are GET requests (doubtful they are something else).
  5. Ensure there is no "Authorization" header.

  6. Ensure there is not already a Cache-Control private or no-store header. If there is, add the following before your "Header append":

    Header unset Cache-Control

  7. Ensure there is a "Etag", "Last-Modified" or "Expires" header. (Which, perhaps you could make a request from the public side of the proxy to check that mod_expire is actually setting an expires header?)

  8. Read through the "What Can Be Cached?" section of the apache caching docs overview.

On a side note, I have disk cache working but I also haven't been able to figure out how to get the %{cache-status} to show in the logs.

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