add parameter to balancer to specify target node list so balancer onl…

…y moves blocks to those nodes

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

@@ -195,6 +195,8 @@ public class Balancer {
       + "\tIncludes only the specified datanodes."
       + "\n\t[-source [-f <hosts-file> | <comma-separated list of hosts>]]"
       + "\tPick only the specified datanodes as source nodes."
+      + "\n\t[-target [-f <hosts-file> | <comma-separated list of hosts>]]"
+      + "\tPick only the specified datanodes as target nodes."
       + "\n\t[-blockpools <comma-separated list of blockpool ids>]"
       + "\tThe balancer will only run on blockpools included in this list."
       + "\n\t[-idleiterations <idleiterations>]"
@@ -222,6 +224,7 @@ public class Balancer {
   private final NameNodeConnector nnc;
   private final BalancingPolicy policy;
   private final Set<String> sourceNodes;
+  private final Set<String> targetNodes;
   private final boolean runDuringUpgrade;
   private final double threshold;
   private final long maxSizeToMove;
@@ -350,6 +353,7 @@ static int getFailedTimesSinceLastSuccessfulBalance() {
     this.threshold = p.getThreshold();
     this.policy = p.getBalancingPolicy();
     this.sourceNodes = p.getSourceNodes();
+    this.targetNodes = p.getTargetNodes();
     this.runDuringUpgrade = p.getRunDuringUpgrade();
     this.sortTopNodes = p.getSortTopNodes();
 
@@ -408,6 +412,7 @@ private long init(List<DatanodeStorageReport> reports) {
     for(DatanodeStorageReport r : reports) {
       final DDatanode dn = dispatcher.newDatanode(r.getDatanodeInfo());
       final boolean isSource = Util.isIncluded(sourceNodes, dn.getDatanodeInfo());
+      final boolean isTarget = Util.isIncluded(targetNodes, dn.getDatanodeInfo());
       for(StorageType t : StorageType.getMovableTypes()) {
         final Double utilization = policy.getUtilization(r, t);
         if (utilization == null) { // datanode does not have such storage type
@@ -421,6 +426,12 @@ private long init(List<DatanodeStorageReport> reports) {
               + " but it is not specified as a source; skipping it.");
           continue;
         }
+        if (utilization <= average && !isTarget) {
+          LOG.info(dn + "[" + t + "] has utilization=" + utilization
+              + " <= average=" + average
+              + " but it is not specified as a target; skipping it.");
+          continue;
+        }
 
         final double utilizationDiff = utilization - average;
         final long capacity = getCapacity(r, t);
@@ -804,6 +815,7 @@ static private int doBalance(Collection<URI> namenodes,
     LOG.info("included nodes = " + p.getIncludedNodes());
     LOG.info("excluded nodes = " + p.getExcludedNodes());
     LOG.info("source nodes = " + p.getSourceNodes());
+    LOG.info("target nodes = " + p.getTargetNodes());
     checkKeytabAndInit(conf);
     System.out.println("Time Stamp               Iteration#"
         + "  Bytes Already Moved  Bytes Left To Move  Bytes Being Moved"
@@ -1034,6 +1046,10 @@ static BalancerParameters parse(String[] args) {
               Set<String> sourceNodes = new HashSet<>();
               i = processHostList(args, i, "source", sourceNodes);
               b.setSourceNodes(sourceNodes);
+            } else if ("-target".equalsIgnoreCase(args[i])) {
+              Set<String> targetNodes = new HashSet<>();
+              i = processHostList(args, i, "target", targetNodes);
+              b.setTargetNodes(targetNodes);
             } else if ("-blockpools".equalsIgnoreCase(args[i])) {
               Preconditions.checkArgument(
                   ++i < args.length,

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

@@ -37,6 +37,11 @@ final class BalancerParameters {
    * source nodes.
    */
   private final Set<String> sourceNodes;
+  /**
+   * If empty, any node can be a target; otherwise, use only these nodes as
+   * target nodes.
+   */
+  private final Set<String> targetNodes;
   /**
    * A set of block pools to run the balancer on.
    */
@@ -63,6 +68,7 @@ private BalancerParameters(Builder builder) {
     this.excludedNodes = builder.excludedNodes;
     this.includedNodes = builder.includedNodes;
     this.sourceNodes = builder.sourceNodes;
+    this.targetNodes = builder.targetNodes;
     this.blockpools = builder.blockpools;
     this.runDuringUpgrade = builder.runDuringUpgrade;
     this.runAsService = builder.runAsService;
@@ -94,6 +100,10 @@ Set<String> getSourceNodes() {
     return this.sourceNodes;
   }
 
+  Set<String> getTargetNodes() {
+    return this.targetNodes;
+  }
+
   Set<String> getBlockPools() {
     return this.blockpools;
   }
@@ -119,12 +129,13 @@ public String toString() {
     return String.format("%s.%s [%s," + " threshold = %s,"
         + " max idle iteration = %s," + " #excluded nodes = %s,"
         + " #included nodes = %s," + " #source nodes = %s,"
+        + " #target nodes = %s,"
         + " #blockpools = %s," + " run during upgrade = %s,"
         + " sort top nodes = %s,"
         + " hot block time interval = %s]",
         Balancer.class.getSimpleName(), getClass().getSimpleName(), policy,
         threshold, maxIdleIteration, excludedNodes.size(),
-        includedNodes.size(), sourceNodes.size(), blockpools.size(),
+        includedNodes.size(), sourceNodes.size(), targetNodes.size(), blockpools.size(),
         runDuringUpgrade, sortTopNodes, hotBlockTimeInterval);
   }
 
@@ -137,6 +148,7 @@ static class Builder {
     private Set<String> excludedNodes = Collections.<String> emptySet();
     private Set<String> includedNodes = Collections.<String> emptySet();
     private Set<String> sourceNodes = Collections.<String> emptySet();
+    private Set<String> targetNodes = Collections.<String> emptySet();
     private Set<String> blockpools = Collections.<String> emptySet();
     private boolean runDuringUpgrade = false;
     private boolean runAsService = false;
@@ -181,6 +193,11 @@ Builder setSourceNodes(Set<String> nodes) {
       return this;
     }
 
+    Builder setTargetNodes(Set<String> nodes) {
+      this.targetNodes = nodes;
+      return this;
+    }
+
     Builder setBlockpools(Set<String> pools) {
       this.blockpools = pools;
       return this;

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

@@ -1247,6 +1247,14 @@ public void testBalancerCliParseWithWrongParams() {
     } catch (IllegalArgumentException ignored) {
       // expected
     }
+
+    parameters = new String[] {"-target"};
+    try {
+      Balancer.Cli.parse(parameters);
+      fail(reason + " for -target parameter");
+    } catch (IllegalArgumentException ignored) {
+      // expected
+    }
   }
 
   @Test