[squid-users] Re: refresh_pattern question

On Wed, 23 Dec 2009 15:10:34 -0800
Manjusha Maddala <mmaddala25_at_nextag.com> wrote:

> Hi,
>
> >From squid.conf,
> refresh_pattern . 21600 100% 21600 override-expire
>
> That is, a cached page is fresh if its age in cache < 15 days
> (21600=15*24*60).

not quite, an object without an explicit expiry time, but that can be
validated, could be stale in less than 15 days.

see override-lastmod

> I noticed that sending HTTP requests to pages older than 30 days
> result in TCP_REFRESH_MISS while requests for pages cached in the
> last 30 days either result in TCP_HIT or TCP_MISS. Since the min time
> for refresh_pattern is 15days, shouldn't it be like pages older than
> 15days should be validated against the parent
> (REFRESH_MISS/REFRESH_HIT) while all other pages are either TCP_HIT
> or TCP_MISS. How did the limit change from 15 to 30? Has anybody else
> seen such an anamoly?

It's not an anomally - from the sample squid.conf file:

          override-expire enforces min age even if the server
          sent an explicit expiry time
          ...
          Note: this does not enforce staleness - it only extends
          freshness / min. If the server returns a Expires time which
          is longer than your max time, Squid will still consider
          the object fresh for that period of time.

 
> Also, if there's no refresh_pattern matching a URI, how would Squid
> process that HTTP request? Would it get a fresh copy from the parent
> or will it return the cached copy?

Presumably the heuristic algorithm for freshness would be disabled
and anything without an explicit expiry time would be stale. It's not
really a sensible thing to do though.

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Received on Thu Dec 24 2009 - 00:11:05 MST