@Override
  protected void rollbackState(MasterProcedureEnv env, TState state)
    throws IOException, InterruptedException {
    if (state == getInitialState()) {
      // actually the peer related operations has no rollback, but if we haven't done any
      // modifications on the peer storage yet, we can just return.
      return;
    }
    throw new UnsupportedOperationException();
  }
Base class for replication peer related procedures which do not need to hold locks(for most of
the sub procedures).
hbase-server/src/main/java/org/apache/hadoop/hbase/master/replication/AbstractPeerNoLockProcedure.java