Site cache doesn't cache in a per-database basis

[German M. Bravo]

The cache for Site (SITE_CACHE) should cache site objects for the database the object comes from. If there is a router in place and the current site is retrieved from one database, a second call for getting the current site from a different database will return the wrong object for that database.

Instead of using SITE_CACHE the way it's currently done, I propose using the same caching scheme as the one used in ContentType's _cache.

[Tim Graham]

I'm not sure I understand the problem completely. Are you saying that in database A you could have (site_id=1, domain=example.com) and in database B (site_id=1, domain=example2.com)? Could you expand a bit on the use case and how you ran into this?

[Tim Graham]

As discussed in IRC, #15089 may solve the use case here (allowing lookup of the current site based on request.get_host()). If not, we need to decide whether we'd officially support this particular configuration of contrib.sites. While caching the site based on database seems valid, I'm opposed to adding complexity unless there's a valid use case.