@Override
  protected PeerModificationState nextStateAfterRefresh() {
    return peerConfig.isSerial()
      ? PeerModificationState.SERIAL_PEER_REOPEN_REGIONS
      : super.nextStateAfterRefresh();
  }
The procedure for adding a new replication peer.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/replication/AddPeerProcedure.java