[squid-users] RE: Incorrect content being returned

Apologies for re-posting, but we are still seeing these problems, and
having trouble identifying the error. Any help would be... helpful.

Thank you,

Jonathan

> -----Original Message-----
 
 
Greetings from a new member of the list.

     I'm working with a medium-sized site that uses squid as a
transparent reverse-proxy cache for its content. We are running
squid-2.4.STABLE7 on FreeBSD 4.0, and the squid servers are caching
content for an array of apache servers. The site is actually comprised
of several sites, each site with it's own array of squids, and we notice
that the squid servers for the largest site are sometimes returning the
wrong content in response to user requests. (That is, the user asks for
contant from domain1.foo.com/, but instead receives content for
domain2.foo.com instead) We believe (from looking at the apache logs)
that when this happens, the squids are actually asking the apache
servers for content using the wrong URL. We're seeing several million
page views per day; this sort of error seems to happen less than 30
times per day, and seems to resolve itself quickly (within 30 seconds)

     Some other facts about our squid servers that we believe might be
contributing:

         - Our larger sites have site a lot of content, so the squid
servers typically have about 200K-400K StoreEntries
         - Even with so many StoreEntries, our squid servers have a
pretty low cache hit ratio (we're currently working to bring it up, but
it's about 40-50% right now)
         - We have 6 squid servers proxying information that is contained
on 28 apache servers, and a redirector program which points the squid to
the correct server based on the domain name in the URL. We were
initially suspicious of the redirector; however, our redirector log
files seem to indictate that the redirector is working correctly; plus,
we use the exact same redirector on squid servers that don't seem to
have the problem.

      What we have already done:
         - Instrumented the redirector to confirm that it's passing back
the correct values to squid
         - Reduced the size of the cache (this actually seemed to make
things worse)
        - Examined the squid logs and corresponding apache logs (this is
where we discovered that squid may be fetching content from the wrong
URL)

      What we are currently doing:
         - Further instrumenting the redirector
         - Trying to increase the disk space on the squids to increase
the cache-hit ratio (so far, this hasn't helped much)
         - Trying to reduce the number of objects that each squid has to
cache

      I'd appreciate any comments on how to track the problem down
further or resolve it.

Best,
 
Jonathan
Received on Wed Jul 24 2002 - 20:24:33 MDT