private void checkSyncReplicationPeerConfigConflict(ReplicationPeerConfig peerConfig)
    throws DoNotRetryIOException {
    for (TableName tableName : peerConfig.getTableCFsMap().keySet()) {
      for (Map.Entry<String, ReplicationPeerDescription> entry : peers.entrySet()) {
        ReplicationPeerConfig rpc = entry.getValue().getPeerConfig();
        if (rpc.isSyncReplication() && rpc.getTableCFsMap().containsKey(tableName)) {
          throw new DoNotRetryIOException(
            "Table " + tableName + " has been replicated by peer " + entry.getKey());
        }
      }
    }
  }
Returns the old desciption of the peer
hbase-server/src/main/java/org/apache/hadoop/hbase/master/replication/ReplicationPeerManager.java