Add Redis cache backend.

[Dulmandakh]

I think that it would be best to have built-in support for Redis caching in Django, as it's getting more popular and has other use cases than just caching. And I found that most of the features overlap with memcached. So I think that it might be better to refactor BaseMemcachedCache to be base for KV engines, and use it for both Memcached and Redis, to reduce code duplication.

I would like to start discussion about best approach adding Redis support into Django. Also I can work on this if approved.

[Mariusz Felisiak]

Thanks for this proposition. There already exists ​django-redis-cache 3rd party package with a Redis cache backend for Django. I don't think that we should move it into core. You can try to start a discussion on the ​django-developers mailing list if you feel that we can reach a different consensus.

[Mariusz Felisiak]

​Discussion on django-developers.

[Carlton Gibson]

It's worth quoting Aymeric's post on the mailing list:

To move this forwards, my suggestion would be to write a DEP, to flesh out the rationale for a built-in solution, and to focus on the breadth of functionality the built-in backend would support. My preference would be a basic set of features, like the other cache backends. I believe that's what django-redis-cache does. This will leave room for third-party packages like django-redis to provide more advanced features. To give a concrete example, like other cache and database backends, a redis backend could provide persistent connections but not implement a connection pool. Until now Django has left the management of connection pools to third-party packages.