Re: [squid-users] purging variants

See programmers guide for an overview of the meta header tlv format, and
the source for the fine details..

Regards
Henrik

mån 2006-03-27 klockan 10:31 -0500 skrev lawrence wang:
> thanks for the clarification. looks like i have some hacking to do.
> so, are these squid object headers documented, like at what offset i
> should look to see if an object is a variant, or should i just dive
> into the code?
>
> On 3/18/06, Henrik Nordstrom <henrik@henriknordstrom.net> wrote:
> > lör 2006-03-18 klockan 08:41 -0500 skrev lawrence wang:
> > > I see. But maybe I've phrased this wrong... It seems like when the
> > > purge tool runs, it does find all the different variants for a given
> > > URL and runs requests against each of them; of course the variants
> > > which require specific headers return 404's when those are not found
> > > in the request. Perhaps there's a way to relax this check without
> > > breaking anything else?
> >
> > The PURGE tool must send the correct headers, or Squid won't know what
> > to do. It's not a check, it's how things work. Squid-2.5 does not know
> > what variants there is for a given URL, no more than it knows what URLs
> > there is in the cache. All it knows to do is "OK, I now have these
> > request headers and URL given to me from the client, is there a matching
> > object". Without the headers it can not find or know the variant.
> > Without the headers all Squid-2.5 find is that the object varies, but
> > have no means of finding the variants. Note of warning: If you PURGE
> > without the variant headers then Squid-2.5 forgets that the object
> > varies and the remaining cached variants of the object can not be
> > reached until Squid has again learned that the object varies by seeing a
> > Vary header response from the server. This means that if you purge
> > without the headers then there is no longer any way to purge the
> > variants without first making a request (which will be a cache miss) for
> > the URL.
> >
> > The PURGE tool could be modified to do this I suppose. Only needs to be
> > taught the vary algorithm used by 2.5 and decode this into suitable
> > request headers as part of the purge request sent to Squid. The required
> > information for reconstructing the required headers is found in a meta
> > TLV header of the object and is read by the purge tool. Only that it
> > does not know the meaning of this information and consequently does not
> > make use of it today.
> >
> >
> > Regards
> > Henrik
> >
> >
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