How to use

addVolumeScanner

method

in

org.apache.hadoop.hdfs.server.datanode.BlockScanner

/**
 * Dynamically add new volumes to the existing volumes that this DN manages.
 *
 * @param ref       a reference to the new FsVolumeImpl instance.
 */
void addVolume(FsVolumeReference ref) {
 FsVolumeImpl volume = (FsVolumeImpl) ref.getVolume();
 volumes.add(volume);
 if (blockScanner != null) {
  blockScanner.addVolumeScanner(ref);
 } else {
  // If the volume is not put into a volume scanner, it does not need to
  // hold the reference.
  IOUtils.cleanup(null, ref);
 }
 // If the volume is used to replace a failed volume, it needs to reset the
 // volume failure info for this volume.
 removeVolumeFailureInfo(volume.getStorageLocation());
 FsDatasetImpl.LOG.info("Added new volume: " +
   volume.getStorageID());
}

 blockScanner.addVolumeScanner(ref);
} else {

 blockScanner.addVolumeScanner(ref);
} else {