AttachReplicasToPrimary used to attach replicas to their primaries.

ClassifyNodesByRole use to classify the Nodes by roles.

DispatchReplica aims to dispatch the available redis to replica of the current primaries.

DispatchSlotsToNewPrimaries used to dispatch slots to the new primary nodes.

PlacePrimaries selects primary redis nodes by spreading out the primaries across zones as much as possible.

PlaceReplicas selects replica redis nodes for each primary by spreading out the replicas across zones as much as possible.

SelectPrimaries used to select redis nodes with primary roles.

SelectPrimariesToReplace used to replace currentPrimaries with new redis nodes.