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Add note about Cluster unavailable

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Jan-Erik Rediger 2015-06-16 11:25:39 +02:00
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@ -63,3 +63,10 @@ Yes, Redis' pubsub mechanism is quite good. People get excited about it. But it
## Ok, I understand Pub/Sub, I really want to use it. Does it work with hundred or thousands of subscriptions/clients? ## Ok, I understand Pub/Sub, I really want to use it. Does it work with hundred or thousands of subscriptions/clients?
The mechanism to subscribe to a channel is quite cheap, consider it an constant-time operation. Publish is more expensive, it needs to send to all subscribed clients. For a much more details info read [the mailing list thread](https://groups.google.com/forum/#!topic/redis-db/R09u__3Jzfk). The mechanism to subscribe to a channel is quite cheap, consider it an constant-time operation. Publish is more expensive, it needs to send to all subscribed clients. For a much more details info read [the mailing list thread](https://groups.google.com/forum/#!topic/redis-db/R09u__3Jzfk).
## My Cluster is unavailable when a Master goes down. How to fix?<a id="cluster-unavailable"></a>
If there is no suitable Replica to failover to, the whole Redis Cluster will go into a fail state and won't serve any more queries.
It will become available when all slots are covered again (either by resharding or bringing the old Master back).
You can change this behaviour and always serve queries by setting `cluster-require-full-coverage` to `no`.
See [the default config for more](https://github.com/antirez/redis/blob/821a986643717018cad8af9f35cba49818e60294/redis.conf#L747-L758).