Build a cache of pool and FS information, for faster lookup, than calling Ceph commands each time

[ShyamsundarR]

Currently in the code we fetch poolIDs, FscID each time it is required. This means calling into Ceph multiple times in the case of some requests (say create) or just fetching the same information repeatedly from Ceph across calls.

Instead, the enhancement proposed is to build a cache of pool names and IDs, and similarly for FSNames and it's IDs, for faster lookups.

This would help in quicker response times when creating/deleting PVs and also when mounting the same.

From an acceptance perspective, the solution should improve on existing creation/deletion/mount times of CephCSI across CephFS and RBD plugins.

One caveat to remember is that, as this is a cache, information can go stale. The risk is when a pool or a FSName is deleted and recreated with the same name, and hence its ID on Ceph changes, but this will not be detected by the cache. As a result this may need careful documentation and/or optionally be enabled for service time sensitive workloads.

[dillaman]

Note: this would be handled automatically as part of using native API calls since the MON maps are cached within the librados connection.

[stale]

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[stale]

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