How to use

useDelHint

method

in

org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

@Override
boolean useDelHint(DatanodeStorageInfo delHint,
  DatanodeStorageInfo added, List<DatanodeStorageInfo> moreThanOne,
  Collection<DatanodeStorageInfo> exactlyOne,
  List<StorageType> excessTypes) {
 if (!super.useDelHint(delHint, added, moreThanOne, exactlyOne,
   excessTypes)) {
  // If BlockPlacementPolicyDefault doesn't allow useDelHint, there is no
  // point checking with upgrade domain policy.
  return false;
 }
 return isMovableBasedOnUpgradeDomain(combine(moreThanOne, exactlyOne),
   delHint, added);
}

if (firstOne && useDelHint(delNodeHintStorage, addedNodeStorage,
  moreThanOne, exactlyOne, excessTypes)) {
 cur = delNodeHintStorage;

if (useDelHint(firstOne, delNodeHintStorage, addedNodeStorage,
  moreThanOne, excessTypes)) {
 cur = delNodeHintStorage;

if (useDelHint(firstOne, delNodeHintStorage, addedNodeStorage,
  moreThanOne, excessTypes)) {
 cur = delNodeHintStorage;

@Test
public void testUseDelHint() throws Exception {
 List<StorageType> excessTypes = new ArrayList<StorageType>();
 excessTypes.add(StorageType.ARCHIVE);
 // only consider delHint for the first case
 assertFalse(BlockPlacementPolicyDefault.useDelHint(false, null, null, null,
   null));
 // no delHint
 assertFalse(BlockPlacementPolicyDefault.useDelHint(true, null, null, null,
   null));
 // delHint storage type is not an excess type
 assertFalse(BlockPlacementPolicyDefault.useDelHint(true, storages[0], null,
   null, excessTypes));
 // check if removing delHint reduces the number of racks
 List<DatanodeStorageInfo> chosenNodes = new ArrayList<DatanodeStorageInfo>();
 chosenNodes.add(storages[0]);
 chosenNodes.add(storages[2]);
 excessTypes.add(StorageType.DEFAULT);
 assertTrue(BlockPlacementPolicyDefault.useDelHint(true, storages[0], null,
   chosenNodes, excessTypes));
 // the added node adds a new rack
 assertTrue(BlockPlacementPolicyDefault.useDelHint(true, storages[3],
   storages[5], chosenNodes, excessTypes));
 // removing delHint reduces the number of racks;
 assertFalse(BlockPlacementPolicyDefault.useDelHint(true, storages[3],
   storages[0], chosenNodes, excessTypes));
 assertFalse(BlockPlacementPolicyDefault.useDelHint(true, storages[3], null,
   chosenNodes, excessTypes));
}

@Test
public void testUseDelHint() {
 DatanodeStorageInfo delHint = new DatanodeStorageInfo(
   DFSTestUtil.getLocalDatanodeDescriptor(), new DatanodeStorage("id"));
 List<DatanodeStorageInfo> moreThan1Racks = Arrays.asList(delHint);
 List<StorageType> excessTypes = new ArrayList<StorageType>();
 excessTypes.add(StorageType.DEFAULT);
 Assert.assertTrue(BlockPlacementPolicyDefault.useDelHint(true, delHint,
   null, moreThan1Racks, excessTypes));
 excessTypes.remove(0);
 excessTypes.add(StorageType.SSD);
 Assert.assertFalse(BlockPlacementPolicyDefault.useDelHint(true, delHint,
   null, moreThan1Racks, excessTypes));
}