Re: [squid-users] Squid 2.6.STABLE9 and caching of 302 redirects

On Tue, 6 Feb 2007, Mark Nottingham wrote:

>> [snipped description of problem in which Squid appears to be caching
>> 302 redirects with "pre-expired" Expires: header and then serving them
>> in response to subsequent requests, breaking the authentication
>> service used by many web servers around the university and smaller
>> numbers elsewhere.]

> Hi John,
>
> Just curious -- have you tried using workarounds like
> Cache-Control: max-age=0
> or
> Cache-Control: no-cache
> to see how they behave?

No - I'm not responsible for the authentication software, only for our web
cache, and that hasn't been tried - but unless we've misunderstood what
the HTTP specification says about how the Expires: header should be used
by caches, adding Cache-Control: shouldn't be necessary as the Expires
headers should (in the problem case) just be asserting explicitly the
default non-cacheability of redirects...

Simply omitting the Expires: header appears to avoid the problem, which
also seems to confirm the problem is with Squid caching and then serving
explicitly pre-expired redirects - though that's not an instant solution
for the problem, just as a fixed version of Squid would not be an instant
solution, since in both cases having a fixed version available is much
easier than getting it installed in all the relevant places.

                                 John

-- 
John Line - web & news development, University of Cambridge Computing Service