Extension for redis cluster mode

[AIweimd]

import redis-py-cluster==2.0.0
CACHE_TYPE=rediscluster
Add cluster parameter of string type:
e.g. host1:port1,host2:port2,host3:port3

[sh4nks]

Hi,
thanks for your PR - however I don't want to add any more backends if there is not more demand for one because I am the one who has to maintain all those.

I'll leave this PR open for now and if there is more demand I might merge it.

[DustinMoriarty]

@sh4nks : I support merging this PR. I just created my own backend for cluster mode to use at my company with Elasticache. I was considering submitting a similar PR.

However, I understand that supporting lots of backends can increase maintenance and testing complexity. In that case, would you prefer that each additional backend be a separate package with more of a plugin/extension architecture emphasis
or would it be better for publicly used backends to be maintained within this package?

[gergelypolonkai]

Adding more backends is fun and all, but most authors who do so will abandon their addition as long as it’s merged and the maintainers will have to, well, maintain it.

Since this package already supports using external backend classes, i’d probably go on the plugin/separate package way. It’s the best for everyone.

About this PR, it’s not really a new backend, but the extension of an existing one. I’m with it, too. Maybe it could be incorporated into the plain redis backend?

[sh4nks]

I am thinking about having a section with 'user contributed' backends where we do not offer 'official' support and a section with core backends that are supported by us might be sufficient. Especially if the clients/backends are getting more complex like the RedisSentinel one where testing the client took some more time since I had to setup the redis sentinels.

This one looks kinda simple so I guess we can include it :-)

[sh4nks]

Please add some documentation about the CACHE_REDIS_CLUSTER setting here: https://github.com/sh4nks/flask-caching/blob/master/docs/index.rst#configuring-flask-caching

and about the rediscluster cache after the redissentinel cache here:
https://github.com/sh4nks/flask-caching/blob/master/docs/index.rst#redissentinelcache

[sh4nks]

@AIweimd if you could add this I'd merge the PR.

Please add some documentation about the CACHE_REDIS_CLUSTER setting here: https://github.com/sh4nks/flask-caching/blob/master/docs/index.rst#configuring-flask-caching

and about the rediscluster cache after the redissentinel cache here:
https://github.com/sh4nks/flask-caching/blob/master/docs/index.rst#redissentinelcache

[AIweimd]

The update document is complete.
It is an honor to contribute to this project.

[coveralls]

Coverage decreased (-1.3%) to 78.316% when pulling 5659d6e on AIweimd:master into 062401f on sh4nks:master.

[sh4nks]

@AIweimd
Thanks for adding the documentation but unfortunately you deleted some existing documentation in your latest commit. Please restore it again :-)

[DustinMoriarty]

@sh4nks: thanks for merging! @AIweimd : thanks for developing! I look forward to testing this out and getting it deployed!