Re: 1.1.21: Obey Expires: in refresh_pattern checks. [patch]

Henrik Nordstrom writes:

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>In 1.1.21 the refresh check logic currently is
>
> FRESH if age < min
> STALE if expires < now
> STALE if age > max
> FRESH if lm-factor < percent
>
>Overriding Expires: in this way is a violation agains HTTP.
>
>The logic should be
>
> STALE if expires < now
> FRESH if age < min
> STALE if age > max
> FRESH if lm-factor < percent
>
>Note that the min age is still useful for objects without a explicit
>Expires: header (i.e. new objects on a server not abusing Expires:).
>
>If we are to override Expires: then it should be required that the
>administrator knows that he does this, and the Expires: header should be
>rewritten to reflect the overridden value (or client caches get
>confused).
>
>This could be done by introducing a extra keyword in refresh_pattern
>that overrides Expires: to be at least min age. When this rule is
>activated Expires: should be rewritten to reflect this.
>
>Personally I object the whole idea of overriding Expires, but I do
>understand why people may whish to do so. It is in the same grey area as
>banner filtering, but less obvious to the client.

I can't apply this until we have a way to let people override
the expires value.

Other thoughts:

        * we could log WARNINGS in cache.log for every refresh
          pattern which causes a violation.

        * The squid.conf comments for refresh_pattern should/could
          be expanded to make it obvious that non-zero MIN value
          violates HTTP.

        * we should be using the HTTP/1.1 WARNING reply headers.

Duane W.
Received on Tue Jul 29 2003 - 13:15:51 MDT