[squid-users] Vedr.: Re: Vedr.: Re: [squid-users] headers.. how to override them - so that it cachesthe url?

From: Klavs Klavsen <ktk@dont-contact.us>
Date: Thu, 29 Nov 2001 11:28:45 +0100

Hi Henrik,

I can tell you what we are doing with squid - as a reverse proxy.

We control the backend servers, and as such - we know everytime a given
page needs to be updated..

What we are about to implement is a backend system that tells squid (by
PURGEing) to refresh a URL - otherwise everything static is cached -

This does mean that squid acts more as a webserver - than a cache.. but
hey, that's what reverse proxy's do..

The reason we choose this solution is that have 20+ sites running.. and the
backend for each of these take a lot of Machine power - when each has to be
redundant, and
we (due to mod_perl ram usage) can't run all sites on every machine..

This problem will be completely minimized, as there will be no more
user-dependant extra-load.. (apart from the few dynamic pages - like search
and personlized pages but that's only 5% of the load..)..

In this aspect it is very good to be able to tell browsers not to cache
something.. or to tell them to only cache it for 1 min.. as we deliver news
the instant updating part is very important.. :-)

I hope you see what I mean..


Klavs Klavsen wrote:

> If you are talking about squid as a web proxy.. then yes..

And a yes it is then. A very strong one.

> but when squid is acting as an origin server - it is very important to be
> to tell browsers and other proxy's out there - NOT to cache.. and some of
> them don't necessarily handle Expire: immediately very well..
> so one would like to send them a Pragma: No-cache.. but still.. when I
> generate this in my backend - I don't want my Reverse Proxy Squid
> to NOT cache the pages..

I partly agree, but even then it has to be done in controlled manners.
The interactions between a origin server and it's surrogate cache needs
to be thought over proper, and then some time needs to be spent on
having Squid and the origin servers implement these interactions
correcly. So far noone has been willing to put the effort or resources
needed to complete such a task for Squid. Such a task, if done proper,
will result in a checklist on how origin servers SHOULD behave to
interact proper with the surrogate, and a couple ot knobs in Squid to
tune things.

The concern I expressed earlier is that these types of overrides does
not ever belong in a proxy, and even having the possibility to enable
them may be bad enought. There is a very obvious conflict between the
two applications of Squid.

Received on Thu Nov 29 2001 - 03:28:44 MST

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