@Override
  protected void postPeerModification(MasterProcedureEnv env)
    throws IOException, ReplicationException {
    if (oldPeerConfig.isSerial() && !peerConfig.isSerial()) {
      env.getReplicationPeerManager().removeAllLastPushedSeqIds(peerId);
    }
    LOG.info("Successfully updated peer config of {} to {}", peerId, peerConfig);
    MasterCoprocessorHost cpHost = env.getMasterCoprocessorHost();
    if (cpHost != null) {
      cpHost.postUpdateReplicationPeerConfig(peerId, peerConfig);
    }
  }
The procedure for updating the config for a replication peer.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/replication/UpdatePeerConfigProcedure.java