class BlockScanner {

  @VisibleForTesting
  synchronized VolumeScanner.Statistics getVolumeStats(String volumeId) {
    VolumeScanner scanner = scanners.get(volumeId);
    if (scanner == null) {
      return null;
    }
    return scanner.getStatistics();
  }

  public  BlockScanner(DataNode datanode, Configuration conf);

}