we have been using apache 1.3 as a caching reverse proxy in front of mod_perl backend servers for several years, and it has worked flawlessly. we recently took the leap to upgrade to 2.2, and everything is working generally well, but we are having some issues with on-disk caching using mod_disk_cache.
for each request, we determine which backend server to proxy off to based on various complex criteria, using mod_rewite. but our setup can be generalized as follows: we send "human" traffic to one set of machines and "bot" traffic to another. the content returned for each is a little different, mostly based on things like not including image-heavy widgets and links to pages or section of the site that require user login.
with apache 1.3, this worked swimmingly, as the key for the on-disk cache seemed to be generated based on the proxy target url, as opposed to the canonical request url.
$ sudo grep -rF -m1 '/stories/201007010002.html' ../R/U/dsvSj2WzpWj5Do8S0Lcw:X-URL: http://crawler:8082/stories/201007010002.html ./x/h/EiBz@6Q5ZMJcpUnUqnAg:X-URL: http://backend:8081/stories/201007010002.html
with the move to apache 2.2, it appears, based on the behavior we are seeing, as well as the comments in cache_storage.c, that the default key generation method is based on the canonical request url, taken before the translate name hook runs. the end result is that, based on our setup, we end up with "practical key collisions", although there is not technically a collision. so in the above example, humans might see the cached version of the page as generated for bot consumption, or vice-versa.
looking at the cache key generation methods, and where they are called from, i could not see any way that i could, through the apache configuration, change this behavior. so is there a directive or module that i'm overlooking, or is there even a "simple" patch that i could apply that would get us back to the key generation behavior of 1.3, or something similar?
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