[squid-users] Strange Vary:Cookie behaviour between Squid and IE

Here is a situation which I have come across with Squid which may be a
misunderstanding/abuse of Squid on my part or a bug.

I have Squid 2.5 stable acting as a a reverse proxy for a zope instance. In
Zope I have specified in the Vary tag as "Accept-Encoding, Cookie". Zope was
setup to send a PURGE to Squid when it's content got changed.

Zope normally sets a cookie for all browsers accessing it. It also by default
sets a cookie when a user is authenticated.

The Squid cache seems to work fine for Firefox and Konqueror clients. For IE
we configured the HTTP header so that IE always requested URLs from Squid and
to never touch it's own cache.

However we saw some strange behaviour with IE <->Squid interaction when IE
was the second browser to retrieve a recently PURGEd URL. We used 3 different
browsers for : 1 authenticated to make changes(Firefox), and 2 to browse
content anonymously (IE and Konqueror).
When a URL is PURGEd and IE is the first to load it, then it gets the correct
content. However if Konqueror loads it first, and IE is second then *Squid*
returns the *old* content to IE. I can see this because using the Fiddler
tool for IE I can see that the Content-Length is not correct.
I can also see this by looking at the debug output from Squid and I can see
the particular file in the disk cache which is returned.

I hope that the above makes some sense.

Now, is this a bug in Squid, or an abuse of the Vary tag by me ?

Regards,
CPH
Received on Wed Oct 19 2005 - 13:36:18 MDT