1067045 - Only latest version of 'Vary'ied resource is cached

Status: RESOLVED WONTFIX

(Core :: Networking: Cache, defect)

Description

[Kevin Cox [@kevincox:matrix.org]]

When firefox encounters a resource with a 'Vary' header it replaces the old entry in the cache for the given URI rather then caching it alongside existing resources.

Steps to reproduce:

Assume the resource contains a 'Vary: Foo' header and a long cache ttl.

Request resource with 'Foo: 1' -> Fetch from server.
Request resource with 'Foo: 1' -> Fulfilled from cache.
Request resource with 'Foo: 2' -> Fetch from server.
Request resource with 'Foo: 2' -> Fulfilled from cache.
Request resource with 'Foo: 1' -> Fetch from server.

Expected results.

The final request should be satisfied by the cache as it has been fetched before and was cacheable.

Comment 1

[Patrick McManus [:mcmanus]]

I've always believed this was a useful simplification for a UA (as long as the downside is undercaching rather than caching something inappropriate). What do you have that is varying within the scope of a single UA?

Comment 2

[Honza Bambas (:mayhemer)]

No intention to fix this.  We would need to add the very'ing headers+values to the cache key mapping somehow but we know the values only after the response has arrived.  This would be pretty complicated.  I have to repeat myself again - the cache is not obligated to cache everything, only what's reasonable.