HDFS-17646. Add Option to limit Balancer overUtilized nodes num in each iteration.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/Balancer.java

@@ -208,6 +208,8 @@ public class Balancer {
  + "\n\t[-sortTopNodes]"
  + "\tSort datanodes based on the utilization so "
  + "that highly utilized datanodes get scheduled first."
+ + "\n\t[-limitOverUtilizedNum <specified maximum number of overUtilized datanodes>]"
+ + "\tLimit the maximum number of overUtilized datanodes."
  + "\n\t[-hotBlockTimeInterval]\tprefer to move cold blocks.";
 
  @VisibleForTesting
@@ -227,6 +229,7 @@ public class Balancer {
  private final long maxSizeToMove;
  private final long defaultBlockSize;
  private final boolean sortTopNodes;
+ private final int limitOverUtilizedNum;
  private final BalancerMetrics metrics;
 
  // all data node lists
@@ -352,6 +355,7 @@ static int getFailedTimesSinceLastSuccessfulBalance() {
  this.sourceNodes = p.getSourceNodes();
  this.runDuringUpgrade = p.getRunDuringUpgrade();
  this.sortTopNodes = p.getSortTopNodes();
+ this.limitOverUtilizedNum = p.getLimitOverUtilizedNum();
 
  this.maxSizeToMove = getLongBytes(conf,
  DFSConfigKeys.DFS_BALANCER_MAX_SIZE_TO_MOVE_KEY,
@@ -456,11 +460,18 @@ private long init(List<DatanodeStorageReport> reports) {
  sortOverUtilized(overUtilizedPercentage);
  }
 
+ // Limit the maximum number of overUtilized datanodes
+ // If excludedOverUtilizedNum is greater than 0, The overUtilized nodes num is limited
+ int excludedOverUtilizedNum = Math.max(overUtilized.size() - limitOverUtilizedNum, 0);
+ if (excludedOverUtilizedNum > 0) {
+ limitOverUtilizedNum();
+ }
+
  logUtilizationCollections();
  metrics.setNumOfOverUtilizedNodes(overUtilized.size());
  metrics.setNumOfUnderUtilizedNodes(underUtilized.size());
 
- Preconditions.checkState(dispatcher.getStorageGroupMap().size()
+ Preconditions.checkState(dispatcher.getStorageGroupMap().size() - excludedOverUtilizedNum
  == overUtilized.size() + underUtilized.size() + aboveAvgUtilized.size()
  + belowAvgUtilized.size(),
  "Mismatched number of storage groups");
@@ -484,6 +495,20 @@ private void sortOverUtilized(Map<Source, Double> overUtilizedPercentage) {
  );
  }
 
+ private void limitOverUtilizedNum() {
+ Preconditions.checkState(overUtilized instanceof LinkedList,
+ "Collection overUtilized is not a LinkedList.");
+ LinkedList<Source> list = (LinkedList<Source>) overUtilized;
+
+ LOG.info("Limiting over-utilized nodes num, if using the '-sortTopNodes' param," +
+ " the overUtilized nodes of top will be retained");
+
+ int size = overUtilized.size();
+ for (int i = 0; i < size - limitOverUtilizedNum; i++) {
+ list.removeLast();
+ }
+ }
+
  private static long computeMaxSize2Move(final long capacity, final long remaining,
  final double utilizationDiff, final long max) {
  final double diff = Math.abs(utilizationDiff);
@@ -1071,6 +1096,12 @@ static BalancerParameters parse(String[] args) {
  b.setSortTopNodes(true);
  LOG.info("Balancer will sort nodes by" +
  " capacity usage percentage to prioritize top used nodes");
+ } else if ("-limitOverUtilizedNum".equalsIgnoreCase(args[i])) {
+ Preconditions.checkArgument(++i < args.length,
+ "limitOverUtilizedNum value is missing: args = " + Arrays.toString(args));
+ int limitNum = Integer.parseInt(args[i]);
+ LOG.info("Using a limitOverUtilizedNum of {}", limitNum);
+ b.setLimitOverUtilizedNum(limitNum);
  } else {
  throw new IllegalArgumentException("args = "
  + Arrays.toString(args));

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/BalancerParameters.java

@@ -50,6 +50,8 @@ final class BalancerParameters {
 
  private final boolean sortTopNodes;
 
+ private final int limitOverUtilizedNum;
+
  static final BalancerParameters DEFAULT = new BalancerParameters();
 
  private BalancerParameters() {
@@ -67,6 +69,7 @@ private BalancerParameters(Builder builder) {
  this.runDuringUpgrade = builder.runDuringUpgrade;
  this.runAsService = builder.runAsService;
  this.sortTopNodes = builder.sortTopNodes;
+ this.limitOverUtilizedNum = builder.limitOverUtilizedNum;
  this.hotBlockTimeInterval = builder.hotBlockTimeInterval;
  }
 
@@ -110,6 +113,10 @@ boolean getSortTopNodes() {
  return this.sortTopNodes;
  }
 
+ int getLimitOverUtilizedNum() {
+ return this.limitOverUtilizedNum;
+ }
+
  long getHotBlockTimeInterval() {
  return this.hotBlockTimeInterval;
  }
@@ -120,12 +127,12 @@ public String toString() {
  + " max idle iteration = %s," + " #excluded nodes = %s,"
  + " #included nodes = %s," + " #source nodes = %s,"
  + " #blockpools = %s," + " run during upgrade = %s,"
- + " sort top nodes = %s,"
+ + " sort top nodes = %s," + " limit overUtilized nodes num = %s"
  + " hot block time interval = %s]",
  Balancer.class.getSimpleName(), getClass().getSimpleName(), policy,
  threshold, maxIdleIteration, excludedNodes.size(),
  includedNodes.size(), sourceNodes.size(), blockpools.size(),
- runDuringUpgrade, sortTopNodes, hotBlockTimeInterval);
+ runDuringUpgrade, sortTopNodes, limitOverUtilizedNum, hotBlockTimeInterval);
  }
 
  static class Builder {
@@ -141,6 +148,7 @@ static class Builder {
  private boolean runDuringUpgrade = false;
  private boolean runAsService = false;
  private boolean sortTopNodes = false;
+ private int limitOverUtilizedNum = Integer.MAX_VALUE;
  private long hotBlockTimeInterval = 0;
 
  Builder() {
@@ -201,6 +209,11 @@ Builder setSortTopNodes(boolean shouldSortTopNodes) {
  return this;
  }
 
+ Builder setLimitOverUtilizedNum(int limitOverUtilizedNum) {
+ this.limitOverUtilizedNum = limitOverUtilizedNum;
+ return this;
+ }
+
  BalancerParameters build() {
  return new BalancerParameters(this);
  }

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md

@@ -293,6 +293,7 @@ Usage:
   [-runDuringUpgrade]
   [-asService]
   [-sortTopNodes]
+  [-limitOverUtilizedNum <specified maximum number of overUtilized datanodes>]
   [-hotBlockTimeInterval <specified time interval>]
 
 | COMMAND\_OPTION | Description |
@@ -307,6 +308,7 @@ Usage:
 | `-runDuringUpgrade` | Whether to run the balancer during an ongoing HDFS upgrade. This is usually not desired since it will not affect used space on over-utilized machines. |
 | `-asService` | Run Balancer as a long running service. |
 | `-sortTopNodes` | Sort datanodes based on the utilization so that highly utilized datanodes get scheduled first. |
+| `-limitOverUtilizedNum` | Limit the maximum number of overUtilized datanodes. |
 | `-hotBlockTimeInterval` | Prefer moving cold blocks i.e blocks associated with files accessed or modified before the specified time interval. |
 | `-h`\|`--help` | Display the tool usage and help information and exit. |
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/balancer/TestBalancerLongRunningTasks.java

@@ -672,6 +672,98 @@ public void testBalancerWithSortTopNodes() throws Exception {
  assertEquals(900, maxUsage);
  }
 
+ @Test(timeout = 60000)
+ public void testBalancerWithLimitOverUtilizedNum() throws Exception {
+ final Configuration conf = new HdfsConfiguration();
+ // Init the config (block size to 100)
+ initConf(conf);
+ conf.setInt(DFS_HEARTBEAT_INTERVAL_KEY, 30000);
+
+ final long totalCapacity = 1000L;
+ final int diffBetweenNodes = 50;
+
+ // Set up the nodes with two groups:
+ // 5 over-utilized nodes with 80%, 85%, 90%, 95%, 100% usage
+ // 2 under-utilized nodes with 0%, 5% usage
+ // With sortTopNodes and limitOverUtilizedNum option, 100% used ones will be chosen
+ final int numOfOverUtilizedDn = 5;
+ final int numOfUnderUtilizedDn = 2;
+ final int totalNumOfDn = numOfOverUtilizedDn + numOfUnderUtilizedDn;
+ final long[] capacityArray = new long[totalNumOfDn];
+ Arrays.fill(capacityArray, totalCapacity);
+
+ try (MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf)
+ .numDataNodes(totalNumOfDn)
+ .simulatedCapacities(capacityArray)
+ .build()) {
+ cluster.setDataNodesDead();
+ List<DataNode> dataNodes = cluster.getDataNodes();
+ // Create top used nodes
+ for (int i = 0; i < numOfOverUtilizedDn; i++) {
+ // Bring one node alive
+ DataNodeTestUtils.triggerHeartbeat(dataNodes.get(i));
+ DataNodeTestUtils.triggerBlockReport(dataNodes.get(i));
+ // Create nodes with: 80%, 85%, 90%, 95%, 100%
+ int nodeCapacity = (int) totalCapacity - diffBetweenNodes * (numOfOverUtilizedDn - i - 1);
+ TestBalancer.createFile(cluster, new Path("test_big" + i), nodeCapacity, (short) 1, 0);
+ cluster.setDataNodesDead();
+ }
+
+ // Create under utilized nodes
+ for (int i = numOfUnderUtilizedDn - 1; i >= 0; i--) {
+ int index = i + numOfOverUtilizedDn;
+ // Bring one node alive
+ DataNodeTestUtils.triggerHeartbeat(dataNodes.get(index));
+ DataNodeTestUtils.triggerBlockReport(dataNodes.get(index));
+ // Create nodes with: 5%, 0%
+ int nodeCapacity = diffBetweenNodes * i;
+ TestBalancer.createFile(cluster, new Path("test_small" + i), nodeCapacity, (short) 1, 0);
+ cluster.setDataNodesDead();
+ }
+
+ // Bring all nodes alive
+ cluster.triggerHeartbeats();
+ cluster.triggerBlockReports();
+ cluster.waitFirstBRCompleted(0, 6000);
+
+ final BalancerParameters balancerParameters = Balancer.Cli.parse(new String[] {
+ "-policy", BalancingPolicy.Node.INSTANCE.getName(),
+ "-threshold", "1",
+ "-sortTopNodes",
+ "-limitOverUtilizedNum", "1"
+ });
+
+ client = NameNodeProxies.createProxy(conf, cluster.getFileSystem(0)
+ .getUri(), ClientProtocol.class)
+ .getProxy();
+
+ // Set max-size-to-move to small number
+ // so only top two nodes will be chosen in one iteration
+ conf.setLong(DFS_BALANCER_MAX_SIZE_TO_MOVE_KEY, 99L);
+ final Collection<URI> namenodes = DFSUtil.getInternalNsRpcUris(conf);
+ List<NameNodeConnector> connectors =
+ NameNodeConnector.newNameNodeConnectors(namenodes, Balancer.class.getSimpleName(),
+ Balancer.BALANCER_ID_PATH, conf, BalancerParameters.DEFAULT.getMaxIdleIteration());
+ final Balancer balancer = new Balancer(connectors.get(0), balancerParameters, conf);
+ Balancer.Result balancerResult = balancer.runOneIteration();
+
+ cluster.triggerDeletionReports();
+ cluster.triggerBlockReports();
+ cluster.triggerHeartbeats();
+
+ DatanodeInfo[] datanodeReport =
+ client.getDatanodeReport(HdfsConstants.DatanodeReportType.ALL);
+ long maxUsage = 0;
+ for (int i = 0; i < totalNumOfDn; i++) {
+ maxUsage = Math.max(maxUsage, datanodeReport[i].getDfsUsed());
+ }
+ // The maxUsage value is 950, only 100% of the nodes will be balanced
+ assertEquals(950, maxUsage);
+ assertTrue("BalancerResult is not as expected. " + balancerResult,
+ (balancerResult.getBytesAlreadyMoved() == 100 && balancerResult.getBlocksMoved() == 1));
+ }
+ }
+
  @Test(timeout = 100000)
  public void testMaxIterationTime() throws Exception {
  final Configuration conf = new HdfsConfiguration();