Re: [squid-users] Revalidation question

On Friday 12 September 2003 22.47, Michael Migdol wrote:

> Is this a bug, or expected behavior? If this is expected behavior,
> can someone please point me to whatever spec indicates that this is
> expected behavior? Is there a config parameter somewhere that we
> are missing?

It is sort of a bug. Squid is supposed to add a Warning header to the
response headers if revalidation fails and Squid gives stale
information to the client, but the Warning header has not yet been
implemented in Squid.

The X-Squid-Error header you saw was part of an internal error message
never sent to the client. It is part of the internal error response
to the If-Modified-Since request initiated by Squid to validate the
already cached object.

Apart from the missing Warning header Squid is operating inside the
HTTP specifications. A If-Modified-Since header is "hop-by-hop" and
does not alone guarantee the client will get the latest copy. When
sent to a proxy-cache all it guarantees is that the client will get
the latest copy the proxy-cache knows about. If your goal is to get
the latest version then Cache-Control: no-cache should be used in
addition to If-Modified-Since. (Cache-Control: max-age=0 is also
suitable, but there may be bugs in Squid there in case of failed
revalidations, not tested or verified)

Regards
Henrik

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