Re: [squid-users] Question to internal behaviour of squid

> --- Ursprüngliche Nachricht ---
> Von: Robert Borkowski <rborkows@novator.com>
> An: alpheus@gmx.de
> Kopie: squid-users@squid-cache.org
> Betreff: Re: [squid-users] Question to internal behaviour of squid
> Datum: Wed, 20 Jul 2005 13:17:49 -0400
>
> alpheus@gmx.de wrote:
> > Hi,
> >
> > I have a general question to the internal behaviour of squid as a
> reverse
> > proxy:
> >
> > Imagine there is a webserver which uses squid as a reverse proxy to
> serve
> > the content.
> > If a user request a site A for the first time, squid has to request A
> from
> > the server.
> > No let's image that this server needs several seconds to generate the
> site
> > A, e.g. 5 seconds.
> > My question: what happens if a second user (and many more) requests the
> same
> > site A in this 5 second time slot?
> > Does squid request site A again from the server or does it know that
> there
> > is already a pending request?
> >
> > So, it is of interest for me if in such a long time slot a lot of
> identical
> > requests would be sent to the webserver or if squid is maintaining a
> list
> > that already a request is running and subsequent calls are put into a
> queue.
> >
> > Hope, my question is clear!?
> >
> > Thx in advance,
> > alp
> >
>
> Yes, when a new request comes in for an object that is 'in flight', the
> second client will join in on the transfer. One interesting effect is
> that if there is a speed difference between clients, and the object is
> large enough then the faster client will be forced to transfer at the
> same speed as the slower client. This is due to squid having a limit to
> the read-ahead difference between the client and origin server.
>
> The read-ahead amount is tunable in squid3.
>
> I found this out the hard way while fighting a very frustrating and
> intermittent failure at our site :-)
>
> --
> Robert Borkowski
>

Thx Robert,

just to make it clear to me: Each client request for the same object causes
an own request from squid to the server (during the time slot to bring the
object into the cache)? Resulting possibly into a large number of request to
the server for the same object if generating the object takes a long time?

Thx,
alp

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