[squid-users] RE: Incorrect content being returned

Hello again, everyone. I didn't hear much back about this, but I wanted
to let you know about a few more things that we've tried:

- In my original message, I said that we were running 2.4.STABLE7. We
were actually running STABLE6. After upgrading to STABLE7, we saw many
fewer content errors, but still some.
- Last month, we had 6 squids caching the same content. We took about
20% of the content and put it behind its own squid. The lone squid
caching much less content has no errors; the 6 squids caching a little
less content is still producing errors.
- We made no changes to our redirector during this period.

So...

It really seems like we're seeing some problem when the number of
objects behind the cache gets over a million (our 6 squids with errors
have about 600K StoreEntries with a hit rate of about 40%). Has anyone
else experienced something like this? Any suggestions?

-- J

>
> > -----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 Aug 21 2002 - 19:00:52 MDT