public boolean addPeer(String peerId) throws ReplicationException {
    if (this.peerCache.containsKey(peerId)) {
      return false;
    }

    peerCache.put(peerId, createPeer(peerId));
    return true;
  }
Method called after a peer has been connected. It will create a ReplicationPeer to track the
newly connected cluster.
@param peerId a short that identifies the cluster
@return whether a ReplicationPeer was successfully created
@throws ReplicationException if connecting to the peer fails
hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ReplicationPeers.java