ons 2013-07-24 klockan 18:46 -0600 skrev Alex Rousskov: > > > The full logics (still missing from squid-3) involves an n-m map of > > requests to response variants. > > I thought Squid already tries to support that. Or are you talking about > responses with varying Vary header values (discussed further below)?
Squid-2 does, but Squid-3 only keeps a 1-1 map. > > This has direct impact on where Vary logics can be performed. > > Can you elaborate on this point? I think there are ways to support full > Vary logics with and without "all variants are in one store" restrictions. It has an impact on how many store api accesses is needed to resolve a request for a varying URL. > > * Add mapping of request headers to specific response variant > > (identified by ETag). > > AFAIK, this is already supported by adjusting the store key. No, there is no way to query the store which ETags are known for a URL. All it knows is that the URL response varies. > > * Lookup the response matching this specific request. > > This is already supported by looking up the computed key in the store index. Sort of. That lookup is today based on URL + response headers which is correct for objects with no ETag. > > To complicate matters further different responses MAY have different > > Vary header value. But it is not very likely. > > True. To support that, we would need to add a list of Vary header values > to the special Vary object and iterate it, looking up a cache object for > every listed Vary header value. It's a little more complicated than that. > > Or better yet allow the same response body to be > > referenced by multiple responses (simplifies validation logics and aging > > considerably). Response headers is the original response updated with > > header data from the 304 response in response to If-None-Match. > > It feels like this is kind of separate optimization. It can be > restricted to Vary transactions, but does not have to be. I don't think it's separate. It has direct impact on how you can store responses to a varying URL and how to handle cache validation. Regards Henrik
