public SyncReplicationState refreshPeerNewSyncReplicationState(String peerId)
    throws ReplicationException {
    ReplicationPeerImpl peer = peerCache.get(peerId);
    SyncReplicationState newState = peerStorage.getPeerNewSyncReplicationState(peerId);
    peer.setNewSyncReplicationState(newState);
    return newState;
  }
Returns the set of peerIds of the clusters that have been connected and have an underlying
ReplicationPeer.
@return a Set of Strings for peerIds
hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ReplicationPeers.java