On Mon, July 30, 2007 10:40 am, Niklas Edmundsson wrote: >> What may make this workable is the combination of "The body is NOT >> stale" >> with "max-age=0". The danger of not writing the headers is that an >> entity, >> once stale, will not be freshened when the spec says it should, and will >> cause a thundering herd of conditional requests to a backend server. >> This >> issue has been badly understood by some in the past, who suggested that >> the >> ability to update cached entities be removed. We need to make very sure >> that >> by fixing one problem we don't introduce another. > > You missed the condition that the header wasn't expired, right?
Alas wrong - the text above was cut and pasted from what you've quoted below. > To > reiterate: > - The body is NOT stale (ie. HTTP_NOT_MODIFIED when revalidating) > - The on-disk header hasn't expired. > - The request has max-age=0 > > Since the on-disk header hasn't expired AND the body is unchanged, > you'll have the same data in the cache except for the Expires header. The problem as Roy pointed out is that max-age=0 is used by code to freshen caches, even caches that are "almost stale". As I said above, we need to make very sure that by fixing one problem we are not introducing another. Regards, Graham --
