@Override
  protected void updatePeerStorage(MasterProcedureEnv env) throws ReplicationException {
    env.getReplicationPeerManager().addPeer(peerId, peerConfig,
      peerConfig.isSerial() ? false : enabled);
  }
The procedure for adding a new replication peer.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/replication/AddPeerProcedure.java