[squid-users] Hierarchical Squid Cache Freshness

I have a system at work and at home. Both systems are running SuSE 9.2
Professional and have Firefox 1.0.2 configured as the default browser.
The Firefox browser at work is configured to automatically detect proxy
settings for the network while the one at home is configured with an
automatic proxy configuration URL. The same configuration file is used in
both instances.

The configuration file uses the load balancing technique outlined by Duane
Wessel's in "Web Caching". The load balancing occurs between two Squid
child caches. In addition, the configuration file directs some activity
to the pareent cache that sits on the security perimeter for some sites
that are known to have problems with session controls, e.g. they use the
IP address in the IP header instead of the HTTP header.

NetDB is used between each of the child Squid caches and the parent cache
to reduce the volume of network traffic on UDP port 3130. I've noticed
that in this environment that stale data is returned to the browser. I'm
not sure whether this is being caused by Firefox or by the use of NetDB.

When using Mozilla (and Netscape), I recall that there was a configuration
option to check for newer content on every reference to an HTTP object.
This configuration option is not present in Firefox.

The stale data is returned in the instances where NetDB is used to locate
the content. The stale content continues to be returned until a request
is made to the Squid cache storing the content for fresh content. After
looking at the logs, I can identify the system containing the stale
content and use client to force retrieval of fresh content.

Has anyone observed this phenomenon? Is it a problem inherent to Firefox
or is it inherent in the way NetDB functions, e.g. the cache storing the
content is simply requested for the content and not asked to check for
newer content?

I am running Squid 2.5STABLE6 on all Squid servers. I haven't gotten
around to configuring newer versions for the servers. :(

Merton Campbell Crockett

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FN:				Merton Campbell Crockett
ORG:				General Dynamics Advanced Information Systems;
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N:				Crockett;Merton;Campbell
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