@Override
  public void setPriority(final TableName tn) {
    setPriority(
      tn != null && tn.isSystemTable() ? HConstants.SYSTEMTABLE_QOS : HConstants.NORMAL_QOS);
  }
Returns One-shot cell scanner (you cannot back it up and restart)
hbase-client/src/main/java/org/apache/hadoop/hbase/ipc/HBaseRpcControllerImpl.java