Graceful switch between database snapshots

[vasvlasov]

We run kvrocks as a read-only mirror for the data produced offline. The snapshots are relatively large - around 100GB per kvrocks instance.
From time to time we'd like to update the snapshots to supply new data. Is there a good way to do this without bringing kvrocks offline (ideally we'd like to preserve block caches until we warm-up on the data from the new snapshot)?

kvrocks 
---> /db-snapshot-1 (current)
---> /db-snapshot-2 (the one we'd like to switch to)