@Override
    public void onPartitionBecomeDroppedFromOffline(String partitionName) {
      // check if partition exists
      ReplicaId replica = storageManager.getReplica(partitionName);
      if (replica == null) {
        throw new StateTransitionException("Replica " + partitionName + " is not found on current node",
            ReplicaNotFound);
      }
      // remove replica from in-mem data structure. If replica doesn't exist, log info but don't fail the transition
      removeReplica(replica);
    }
{@link PartitionStateChangeListener} to capture changes in partition state.
ambry-server/src/main/java/com/github/ambry/server/StatsManager.java