Feature request: add a cluster-capable version of flushallAsync

[jchambers]

RedisAdvancedClusterCommands has an implementation of flushall that will:

Remove all keys from all databases on all cluster masters with pipelining.

It does not, however, have a matching implementation of flushallAsync, which instead lives in the world of single-node commands. That can lead to some surprising behavior:

connection.sync().flushall(); // Clears the whole cluster, but blocks
connection.sync().flushallAsync(); // Clears just one shard of the cluster asynchronously

To be fair, there is a viable workaround:

connection.sync().masters().commands().flushallAsync(); // Clears the whole cluster asynchronously

…but it's very easy to fall into the trap of thinking you've cleared your whole cluster even if only one shard was cleared. I'm writing to suggest adding a cluster-capable version of flushallAsync() to RedisAdvancedClusterCommands and its async/reactive cousins.

[mp911de]

Great proposal. Do you want to submit a pull request?

[jchambers]

Sure. I may need some help understanding some plumbing, but I'll open a draft and we can work through the specifics there.