RE: [squid-users] Can we use "no-cache" or "max-age=0" to refresh the cached objects

On tor, 2008-10-02 at 10:57 +0200, Christian Tzolov wrote:

> I am scared by the "I believe" part :).
>
> 1. Can we relay on Squid to always update its cached content if the
> response is newer (e.g. response has new Expires date and no other
> validators)?

Yes.

> 2. Squid does not change/optimize its behavior under high load in way
> that could affect assumption (1)?

Under very high load you may in worst case end up with no on-disk copy
of the cached object if an overload condition does not allow writing
objects out to disk..

> 3. If (1) holds is this a (HTTP) standard behavior or Squid
> implementation?

Yes. Or to be exact the standard requires the old copy to be invalidated
if different from the new. There is no requirement to cache the new
representation.

Note however that there is a significant difference between no-cache and
max-age=0:

 * no-cache forces a new retreival, The response is not allowed to be
satisfied from cache.

 * max-age=0 forces a cache validation and allows the old version to be
returned if the server says it's still fresh.

Regards
Henrik