HDFS-6837. Code cleanup for Balancer and Dispatcher. Contributed by Tsz Wo Nicholas Sze.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1617337 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -387,6 +387,9 @@ Release 2.6.0 - UNRELEASED
     HDFS-6828. Separate block replica dispatching from Balancer. (szetszwo via
     jing9)
 
+    HDFS-6837. Code cleanup for Balancer and Dispatcher. (szetszwo via
+    jing9)
+
   OPTIMIZATIONS
 
     HDFS-6690. Deduplicate xattr names in memory. (wang)

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

@@ -44,7 +44,8 @@ import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.StorageType;
-import org.apache.hadoop.hdfs.server.balancer.Dispatcher.BalancerDatanode;
+import org.apache.hadoop.hdfs.server.balancer.Dispatcher.DDatanode;
+import org.apache.hadoop.hdfs.server.balancer.Dispatcher.DDatanode.StorageGroup;
 import org.apache.hadoop.hdfs.server.balancer.Dispatcher.Source;
 import org.apache.hadoop.hdfs.server.balancer.Dispatcher.Task;
 import org.apache.hadoop.hdfs.server.balancer.Dispatcher.Util;
@@ -184,10 +185,10 @@ public class Balancer {
   // all data node lists
   private final Collection<Source> overUtilized = new LinkedList<Source>();
   private final Collection<Source> aboveAvgUtilized = new LinkedList<Source>();
-  private final Collection<BalancerDatanode.StorageGroup> belowAvgUtilized
+  private final Collection<StorageGroup> belowAvgUtilized
-      = new LinkedList<BalancerDatanode.StorageGroup>();
+      = new LinkedList<StorageGroup>();
-  private final Collection<BalancerDatanode.StorageGroup> underUtilized
+  private final Collection<StorageGroup> underUtilized
-      = new LinkedList<BalancerDatanode.StorageGroup>();
+      = new LinkedList<StorageGroup>();
 
   /* Check that this Balancer is compatible with the Block Placement Policy
    * used by the Namenode.
@@ -209,8 +210,22 @@ public class Balancer {
    * when connection fails.
    */
   Balancer(NameNodeConnector theblockpool, Parameters p, Configuration conf) {
+    final long movedWinWidth = conf.getLong(
+        DFSConfigKeys.DFS_BALANCER_MOVEDWINWIDTH_KEY,
+        DFSConfigKeys.DFS_BALANCER_MOVEDWINWIDTH_DEFAULT);
+    final int moverThreads = conf.getInt(
+        DFSConfigKeys.DFS_BALANCER_MOVERTHREADS_KEY,
+        DFSConfigKeys.DFS_BALANCER_MOVERTHREADS_DEFAULT);
+    final int dispatcherThreads = conf.getInt(
+        DFSConfigKeys.DFS_BALANCER_DISPATCHERTHREADS_KEY,
+        DFSConfigKeys.DFS_BALANCER_DISPATCHERTHREADS_DEFAULT);
+    final int maxConcurrentMovesPerNode = conf.getInt(
+        DFSConfigKeys.DFS_DATANODE_BALANCE_MAX_NUM_CONCURRENT_MOVES_KEY,
+        DFSConfigKeys.DFS_DATANODE_BALANCE_MAX_NUM_CONCURRENT_MOVES_DEFAULT);
+
     this.dispatcher = new Dispatcher(theblockpool, p.nodesToBeIncluded,
-        p.nodesToBeExcluded, conf);
+        p.nodesToBeExcluded, movedWinWidth, moverThreads, dispatcherThreads,
+        maxConcurrentMovesPerNode, conf);
     this.threshold = p.threshold;
     this.policy = p.policy;
   }
@@ -255,7 +270,7 @@ public class Balancer {
     //   over-utilized, above-average, below-average and under-utilized.
     long overLoadedBytes = 0L, underLoadedBytes = 0L;
     for(DatanodeStorageReport r : reports) {
-      final BalancerDatanode dn = dispatcher.newDatanode(r);
+      final DDatanode dn = dispatcher.newDatanode(r);
       for(StorageType t : StorageType.asList()) {
         final Double utilization = policy.getUtilization(r, t);
         if (utilization == null) { // datanode does not have such storage type 
@@ -268,9 +283,9 @@ public class Balancer {
         final long maxSize2Move = computeMaxSize2Move(capacity,
             getRemaining(r, t), utilizationDiff, threshold);
 
-        final BalancerDatanode.StorageGroup g;
+        final StorageGroup g;
         if (utilizationDiff > 0) {
-          final Source s = dn.addSource(t, utilization, maxSize2Move, dispatcher);
+          final Source s = dn.addSource(t, maxSize2Move, dispatcher);
           if (thresholdDiff <= 0) { // within threshold
             aboveAvgUtilized.add(s);
           } else {
@@ -279,7 +294,7 @@ public class Balancer {
           }
           g = s;
         } else {
-          g = dn.addStorageGroup(t, utilization, maxSize2Move);
+          g = dn.addStorageGroup(t, maxSize2Move);
           if (thresholdDiff <= 0) { // within threshold
             belowAvgUtilized.add(g);
           } else {
@@ -328,7 +343,7 @@ public class Balancer {
     logUtilizationCollection("underutilized", underUtilized);
   }
 
-  private static <T extends BalancerDatanode.StorageGroup>
+  private static <T extends StorageGroup>
       void logUtilizationCollection(String name, Collection<T> items) {
     LOG.info(items.size() + " " + name + ": " + items);
   }
@@ -381,8 +396,7 @@ public class Balancer {
    * datanodes or the candidates are source nodes with (utilization > Avg), and
    * the others are target nodes with (utilization < Avg).
    */
-  private <G extends BalancerDatanode.StorageGroup,
+  private <G extends StorageGroup, C extends StorageGroup>
-           C extends BalancerDatanode.StorageGroup>
       void chooseStorageGroups(Collection<G> groups, Collection<C> candidates,
           Matcher matcher) {
     for(final Iterator<G> i = groups.iterator(); i.hasNext();) {
@@ -398,9 +412,8 @@ public class Balancer {
    * For the given datanode, choose a candidate and then schedule it.
    * @return true if a candidate is chosen; false if no candidates is chosen.
    */
-  private <C extends BalancerDatanode.StorageGroup>
+  private <C extends StorageGroup> boolean choose4One(StorageGroup g,
-      boolean choose4One(BalancerDatanode.StorageGroup g,
+      Collection<C> candidates, Matcher matcher) {
-          Collection<C> candidates, Matcher matcher) {
     final Iterator<C> i = candidates.iterator();
     final C chosen = chooseCandidate(g, i, matcher);
   
@@ -418,8 +431,7 @@ public class Balancer {
     return true;
   }
   
-  private void matchSourceWithTargetToMove(Source source,
+  private void matchSourceWithTargetToMove(Source source, StorageGroup target) {
-      BalancerDatanode.StorageGroup target) {
     long size = Math.min(source.availableSizeToMove(), target.availableSizeToMove());
     final Task task = new Task(target, size);
     source.addTask(task);
@@ -430,8 +442,7 @@ public class Balancer {
   }
   
   /** Choose a candidate for the given datanode. */
-  private <G extends BalancerDatanode.StorageGroup,
+  private <G extends StorageGroup, C extends StorageGroup>
-           C extends BalancerDatanode.StorageGroup>
       C chooseCandidate(G g, Iterator<C> candidates, Matcher matcher) {
     if (g.hasSpaceForScheduling()) {
       for(; candidates.hasNext(); ) {
@@ -439,7 +450,7 @@ public class Balancer {
         if (!c.hasSpaceForScheduling()) {
           candidates.remove();
         } else if (matcher.match(dispatcher.getCluster(),
-            g.getDatanode(), c.getDatanode())) {
+            g.getDatanodeInfo(), c.getDatanodeInfo())) {
           return c;
         }
       }
@@ -457,34 +468,15 @@ public class Balancer {
     dispatcher.reset(conf);;
   }
   
-  // Exit status
-  enum ReturnStatus {
-    // These int values will map directly to the balancer process's exit code.
-    SUCCESS(0),
-    IN_PROGRESS(1),
-    ALREADY_RUNNING(-1),
-    NO_MOVE_BLOCK(-2),
-    NO_MOVE_PROGRESS(-3),
-    IO_EXCEPTION(-4),
-    ILLEGAL_ARGS(-5),
-    INTERRUPTED(-6);
-
-    final int code;
-
-    ReturnStatus(int code) {
-      this.code = code;
-    }
-  }
-
   /** Run an iteration for all datanodes. */
-  private ReturnStatus run(int iteration, Formatter formatter,
+  private ExitStatus run(int iteration, Formatter formatter,
       Configuration conf) {
     try {
       final List<DatanodeStorageReport> reports = dispatcher.init();
       final long bytesLeftToMove = init(reports);
       if (bytesLeftToMove == 0) {
         System.out.println("The cluster is balanced. Exiting...");
-        return ReturnStatus.SUCCESS;
+        return ExitStatus.SUCCESS;
       } else {
         LOG.info( "Need to move "+ StringUtils.byteDesc(bytesLeftToMove)
             + " to make the cluster balanced." );
@@ -498,7 +490,7 @@ public class Balancer {
       final long bytesToMove = chooseStorageGroups();
       if (bytesToMove == 0) {
         System.out.println("No block can be moved. Exiting...");
-        return ReturnStatus.NO_MOVE_BLOCK;
+        return ExitStatus.NO_MOVE_BLOCK;
       } else {
         LOG.info( "Will move " + StringUtils.byteDesc(bytesToMove) +
             " in this iteration");
@@ -519,19 +511,19 @@ public class Balancer {
        * Exit no byte has been moved for 5 consecutive iterations.
        */
       if (!dispatcher.dispatchAndCheckContinue()) {
-        return ReturnStatus.NO_MOVE_PROGRESS;
+        return ExitStatus.NO_MOVE_PROGRESS;
       }
 
-      return ReturnStatus.IN_PROGRESS;
+      return ExitStatus.IN_PROGRESS;
     } catch (IllegalArgumentException e) {
       System.out.println(e + ".  Exiting ...");
-      return ReturnStatus.ILLEGAL_ARGS;
+      return ExitStatus.ILLEGAL_ARGUMENTS;
     } catch (IOException e) {
       System.out.println(e + ".  Exiting ...");
-      return ReturnStatus.IO_EXCEPTION;
+      return ExitStatus.IO_EXCEPTION;
     } catch (InterruptedException e) {
       System.out.println(e + ".  Exiting ...");
-      return ReturnStatus.INTERRUPTED;
+      return ExitStatus.INTERRUPTED;
     } finally {
       dispatcher.shutdownNow();
     }
@@ -570,14 +562,14 @@ public class Balancer {
         Collections.shuffle(connectors);
         for(NameNodeConnector nnc : connectors) {
           final Balancer b = new Balancer(nnc, p, conf);
-          final ReturnStatus r = b.run(iteration, formatter, conf);
+          final ExitStatus r = b.run(iteration, formatter, conf);
           // clean all lists
           b.resetData(conf);
-          if (r == ReturnStatus.IN_PROGRESS) {
+          if (r == ExitStatus.IN_PROGRESS) {
             done = false;
-          } else if (r != ReturnStatus.SUCCESS) {
+          } else if (r != ExitStatus.SUCCESS) {
             //must be an error statue, return.
-            return r.code;
+            return r.getExitCode();
           }
         }
 
@@ -590,7 +582,7 @@ public class Balancer {
         nnc.close();
       }
     }
-    return ReturnStatus.SUCCESS.code;
+    return ExitStatus.SUCCESS.getExitCode();
   }
 
   /* Given elaspedTime in ms, return a printable string */
@@ -661,10 +653,10 @@ public class Balancer {
         return Balancer.run(namenodes, parse(args), conf);
       } catch (IOException e) {
         System.out.println(e + ".  Exiting ...");
-        return ReturnStatus.IO_EXCEPTION.code;
+        return ExitStatus.IO_EXCEPTION.getExitCode();
       } catch (InterruptedException e) {
         System.out.println(e + ".  Exiting ...");
-        return ReturnStatus.INTERRUPTED.code;
+        return ExitStatus.INTERRUPTED.getExitCode();
       } finally {
         System.out.format("%-24s ", DateFormat.getDateTimeInstance().format(new Date()));
         System.out.println("Balancing took " + time2Str(Time.now()-startTime));

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

@@ -48,7 +48,6 @@ import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.CommonConfigurationKeys;
-import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.StorageType;
 import org.apache.hadoop.hdfs.protocol.Block;
@@ -63,6 +62,7 @@ import org.apache.hadoop.hdfs.protocol.datatransfer.sasl.SaslDataTransferClient;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.BlockOpResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
+import org.apache.hadoop.hdfs.server.balancer.Dispatcher.DDatanode.StorageGroup;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
 import org.apache.hadoop.hdfs.server.protocol.BlocksWithLocations;
 import org.apache.hadoop.hdfs.server.protocol.BlocksWithLocations.BlockWithLocations;
@@ -91,7 +91,6 @@ public class Dispatcher {
                                                                      // minutes
 
   private final NameNodeConnector nnc;
-  private final KeyManager keyManager;
   private final SaslDataTransferClient saslClient;
 
   /** Set of datanodes to be excluded. */
@@ -100,11 +99,10 @@ public class Dispatcher {
   private final Set<String> includedNodes;
 
   private final Collection<Source> sources = new HashSet<Source>();
-  private final Collection<BalancerDatanode.StorageGroup> targets
+  private final Collection<StorageGroup> targets = new HashSet<StorageGroup>();
-      = new HashSet<BalancerDatanode.StorageGroup>();
 
   private final GlobalBlockMap globalBlocks = new GlobalBlockMap();
-  private final MovedBlocks<BalancerDatanode.StorageGroup> movedBlocks;
+  private final MovedBlocks<StorageGroup> movedBlocks;
 
   /** Map (datanodeUuid,storageType -> StorageGroup) */
   private final StorageGroupMap storageGroupMap = new StorageGroupMap();
@@ -135,8 +133,7 @@ public class Dispatcher {
     }
     
     /** Remove all blocks except for the moved blocks. */
-    private void removeAllButRetain(
+    private void removeAllButRetain(MovedBlocks<StorageGroup> movedBlocks) {
-        MovedBlocks<BalancerDatanode.StorageGroup> movedBlocks) {
       for (Iterator<Block> i = map.keySet().iterator(); i.hasNext();) {
         if (!movedBlocks.contains(i.next())) {
           i.remove();
@@ -150,17 +147,15 @@ public class Dispatcher {
       return datanodeUuid + ":" + storageType;
     }
 
-    private final Map<String, BalancerDatanode.StorageGroup> map
+    private final Map<String, StorageGroup> map = new HashMap<String, StorageGroup>();
-        = new HashMap<String, BalancerDatanode.StorageGroup>();
 
-    BalancerDatanode.StorageGroup get(String datanodeUuid,
+    StorageGroup get(String datanodeUuid, StorageType storageType) {
-        StorageType storageType) {
       return map.get(toKey(datanodeUuid, storageType));
     }
 
-    void put(BalancerDatanode.StorageGroup g) {
+    void put(StorageGroup g) {
-      final String key = toKey(g.getDatanode().getDatanodeUuid(), g.storageType);
+      final String key = toKey(g.getDatanodeInfo().getDatanodeUuid(), g.storageType);
-      final BalancerDatanode.StorageGroup existing = map.put(key, g);
+      final StorageGroup existing = map.put(key, g);
       Preconditions.checkState(existing == null);
     }
 
@@ -177,8 +172,8 @@ public class Dispatcher {
   private class PendingMove {
     private DBlock block;
     private Source source;
-    private BalancerDatanode proxySource;
+    private DDatanode proxySource;
-    private BalancerDatanode.StorageGroup target;
+    private StorageGroup target;
 
     private PendingMove() {
     }
@@ -235,24 +230,24 @@ public class Dispatcher {
      * @return true if a proxy is found; otherwise false
      */
     private boolean chooseProxySource() {
-      final DatanodeInfo targetDN = target.getDatanode();
+      final DatanodeInfo targetDN = target.getDatanodeInfo();
       // if node group is supported, first try add nodes in the same node group
       if (cluster.isNodeGroupAware()) {
-        for (BalancerDatanode.StorageGroup loc : block.getLocations()) {
+        for (StorageGroup loc : block.getLocations()) {
-          if (cluster.isOnSameNodeGroup(loc.getDatanode(), targetDN)
+          if (cluster.isOnSameNodeGroup(loc.getDatanodeInfo(), targetDN)
               && addTo(loc)) {
             return true;
           }
         }
       }
       // check if there is replica which is on the same rack with the target
-      for (BalancerDatanode.StorageGroup loc : block.getLocations()) {
+      for (StorageGroup loc : block.getLocations()) {
-        if (cluster.isOnSameRack(loc.getDatanode(), targetDN) && addTo(loc)) {
+        if (cluster.isOnSameRack(loc.getDatanodeInfo(), targetDN) && addTo(loc)) {
           return true;
         }
       }
       // find out a non-busy replica
-      for (BalancerDatanode.StorageGroup loc : block.getLocations()) {
+      for (StorageGroup loc : block.getLocations()) {
         if (addTo(loc)) {
           return true;
         }
@@ -261,10 +256,10 @@ public class Dispatcher {
     }
 
     /** add to a proxy source for specific block movement */
-    private boolean addTo(BalancerDatanode.StorageGroup g) {
+    private boolean addTo(StorageGroup g) {
-      final BalancerDatanode bdn = g.getBalancerDatanode();
+      final DDatanode dn = g.getDDatanode();
-      if (bdn.addPendingBlock(this)) {
+      if (dn.addPendingBlock(this)) {
-        proxySource = bdn;
+        proxySource = dn;
         return true;
       }
       return false;
@@ -281,14 +276,13 @@ public class Dispatcher {
       DataInputStream in = null;
       try {
         sock.connect(
-            NetUtils.createSocketAddr(target.getDatanode().getXferAddr()),
+            NetUtils.createSocketAddr(target.getDatanodeInfo().getXferAddr()),
             HdfsServerConstants.READ_TIMEOUT);
         /*
          * Unfortunately we don't have a good way to know if the Datanode is
          * taking a really long time to move a block, OR something has gone
          * wrong and it's never going to finish. To deal with this scenario, we
-         * set a long timeout (20 minutes) to avoid hanging the balancer
+         * set a long timeout (20 minutes) to avoid hanging indefinitely.
-         * indefinitely.
          */
         sock.setSoTimeout(BLOCK_MOVE_READ_TIMEOUT);
 
@@ -298,9 +292,10 @@ public class Dispatcher {
         InputStream unbufIn = sock.getInputStream();
         ExtendedBlock eb = new ExtendedBlock(nnc.getBlockpoolID(),
             block.getBlock());
-        Token<BlockTokenIdentifier> accessToken = keyManager.getAccessToken(eb);
+        final KeyManager km = nnc.getKeyManager(); 
+        Token<BlockTokenIdentifier> accessToken = km.getAccessToken(eb);
         IOStreamPair saslStreams = saslClient.socketSend(sock, unbufOut,
-            unbufIn, keyManager, accessToken, target.getDatanode());
+            unbufIn, km, accessToken, target.getDatanodeInfo());
         unbufOut = saslStreams.out;
         unbufIn = saslStreams.in;
         out = new DataOutputStream(new BufferedOutputStream(unbufOut,
@@ -314,21 +309,19 @@ public class Dispatcher {
         LOG.info("Successfully moved " + this);
       } catch (IOException e) {
         LOG.warn("Failed to move " + this + ": " + e.getMessage());
-        /*
+        // Proxy or target may have some issues, delay before using these nodes
-         * proxy or target may have an issue, insert a small delay before using
+        // further in order to avoid a potential storm of "threads quota
-         * these nodes further. This avoids a potential storm of
+        // exceeded" warnings when the dispatcher gets out of sync with work
-         * "threads quota exceeded" Warnings when the balancer gets out of sync
+        // going on in datanodes.
-         * with work going on in datanode.
-         */
         proxySource.activateDelay(DELAY_AFTER_ERROR);
-        target.getBalancerDatanode().activateDelay(DELAY_AFTER_ERROR);
+        target.getDDatanode().activateDelay(DELAY_AFTER_ERROR);
       } finally {
         IOUtils.closeStream(out);
         IOUtils.closeStream(in);
         IOUtils.closeSocket(sock);
 
         proxySource.removePendingBlock(this);
-        target.getBalancerDatanode().removePendingBlock(this);
+        target.getDDatanode().removePendingBlock(this);
 
         synchronized (this) {
           reset();
@@ -342,8 +335,8 @@ public class Dispatcher {
     /** Send a block replace request to the output stream */
     private void sendRequest(DataOutputStream out, ExtendedBlock eb,
         Token<BlockTokenIdentifier> accessToken) throws IOException {
-      new Sender(out).replaceBlock(eb, target.storageType, accessToken, source
+      new Sender(out).replaceBlock(eb, target.storageType, accessToken,
-          .getDatanode().getDatanodeUuid(), proxySource.datanode);
+          source.getDatanodeInfo().getDatanodeUuid(), proxySource.datanode);
     }
 
     /** Receive a block copy response from the input stream */
@@ -368,8 +361,7 @@ public class Dispatcher {
   }
 
   /** A class for keeping track of block locations in the dispatcher. */
-  private static class DBlock extends
+  private static class DBlock extends MovedBlocks.Locations<StorageGroup> {
-      MovedBlocks.Locations<BalancerDatanode.StorageGroup> {
     DBlock(Block block) {
       super(block);
     }
@@ -377,10 +369,10 @@ public class Dispatcher {
 
   /** The class represents a desired move. */
   static class Task {
-    private final BalancerDatanode.StorageGroup target;
+    private final StorageGroup target;
     private long size; // bytes scheduled to move
 
-    Task(BalancerDatanode.StorageGroup target, long size) {
+    Task(StorageGroup target, long size) {
       this.target = target;
       this.size = size;
     }
@@ -391,28 +383,25 @@ public class Dispatcher {
   }
 
   /** A class that keeps track of a datanode. */
-  static class BalancerDatanode {
+  static class DDatanode {
 
     /** A group of storages in a datanode with the same storage type. */
     class StorageGroup {
       final StorageType storageType;
-      final double utilization;
       final long maxSize2Move;
       private long scheduledSize = 0L;
 
-      private StorageGroup(StorageType storageType, double utilization,
+      private StorageGroup(StorageType storageType, long maxSize2Move) {
-          long maxSize2Move) {
         this.storageType = storageType;
-        this.utilization = utilization;
         this.maxSize2Move = maxSize2Move;
       }
 
-      BalancerDatanode getBalancerDatanode() {
+      private DDatanode getDDatanode() {
-        return BalancerDatanode.this;
+        return DDatanode.this;
       }
 
-      DatanodeInfo getDatanode() {
+      DatanodeInfo getDatanodeInfo() {
-        return BalancerDatanode.this.datanode;
+        return DDatanode.this.datanode;
       }
 
       /** Decide if still need to move more bytes */
@@ -447,7 +436,7 @@ public class Dispatcher {
 
       @Override
       public String toString() {
-        return "" + utilization;
+        return getDisplayName();
       }
     }
 
@@ -461,10 +450,10 @@ public class Dispatcher {
 
     @Override
     public String toString() {
-      return getClass().getSimpleName() + ":" + datanode + ":" + storageMap;
+      return getClass().getSimpleName() + ":" + datanode + ":" + storageMap.values();
     }
 
-    private BalancerDatanode(DatanodeStorageReport r, int maxConcurrentMoves) {
+    private DDatanode(DatanodeStorageReport r, int maxConcurrentMoves) {
       this.datanode = r.getDatanodeInfo();
       this.maxConcurrentMoves = maxConcurrentMoves;
       this.pendings = new ArrayList<PendingMove>(maxConcurrentMoves);
@@ -475,18 +464,14 @@ public class Dispatcher {
       Preconditions.checkState(existing == null);
     }
 
-    StorageGroup addStorageGroup(StorageType storageType, double utilization,
+    StorageGroup addStorageGroup(StorageType storageType, long maxSize2Move) {
-        long maxSize2Move) {
+      final StorageGroup g = new StorageGroup(storageType, maxSize2Move);
-      final StorageGroup g = new StorageGroup(storageType, utilization,
-          maxSize2Move);
       put(storageType, g);
       return g;
     }
 
-    Source addSource(StorageType storageType, double utilization,
+    Source addSource(StorageType storageType, long maxSize2Move, Dispatcher d) {
-        long maxSize2Move, Dispatcher balancer) {
+      final Source s = d.new Source(storageType, maxSize2Move, this);
-      final Source s = balancer.new Source(storageType, utilization,
-          maxSize2Move, this);
       put(storageType, s);
       return s;
     }
@@ -528,7 +513,7 @@ public class Dispatcher {
   }
 
   /** A node that can be the sources of a block move */
-  class Source extends BalancerDatanode.StorageGroup {
+  class Source extends DDatanode.StorageGroup {
 
     private final List<Task> tasks = new ArrayList<Task>(2);
     private long blocksToReceive = 0L;
@@ -539,9 +524,8 @@ public class Dispatcher {
      */
     private final List<DBlock> srcBlocks = new ArrayList<DBlock>();
 
-    private Source(StorageType storageType, double utilization,
+    private Source(StorageType storageType, long maxSize2Move, DDatanode dn) {
-        long maxSize2Move, BalancerDatanode dn) {
+      dn.super(storageType, maxSize2Move);
-      dn.super(storageType, utilization, maxSize2Move);
     }
 
     /** Add a task */
@@ -565,7 +549,7 @@ public class Dispatcher {
      */
     private long getBlockList() throws IOException {
       final long size = Math.min(MAX_BLOCKS_SIZE_TO_FETCH, blocksToReceive);
-      final BlocksWithLocations newBlocks = nnc.getBlocks(getDatanode(), size);
+      final BlocksWithLocations newBlocks = nnc.getBlocks(getDatanodeInfo(), size);
 
       long bytesReceived = 0;
       for (BlockWithLocations blk : newBlocks.getBlocks()) {
@@ -579,7 +563,7 @@ public class Dispatcher {
             final String[] datanodeUuids = blk.getDatanodeUuids();
             final StorageType[] storageTypes = blk.getStorageTypes();
             for (int i = 0; i < datanodeUuids.length; i++) {
-              final BalancerDatanode.StorageGroup g = storageGroupMap.get(
+              final StorageGroup g = storageGroupMap.get(
                   datanodeUuids[i], storageTypes[i]);
               if (g != null) { // not unknown
                 block.addLocation(g);
@@ -617,7 +601,7 @@ public class Dispatcher {
     private PendingMove chooseNextMove() {
       for (Iterator<Task> i = tasks.iterator(); i.hasNext();) {
         final Task task = i.next();
-        final BalancerDatanode target = task.target.getBalancerDatanode();
+        final DDatanode target = task.target.getDDatanode();
         PendingMove pendingBlock = new PendingMove();
         if (target.addPendingBlock(pendingBlock)) {
           // target is not busy, so do a tentative block allocation
@@ -670,7 +654,7 @@ public class Dispatcher {
       final long startTime = Time.monotonicNow();
       this.blocksToReceive = 2 * getScheduledSize();
       boolean isTimeUp = false;
-      int noPendingBlockIteration = 0;
+      int noPendingMoveIteration = 0;
       while (!isTimeUp && getScheduledSize() > 0
           && (!srcBlocks.isEmpty() || blocksToReceive > 0)) {
         final PendingMove p = chooseNextMove();
@@ -699,11 +683,11 @@ public class Dispatcher {
             return;
           }
         } else {
-          // source node cannot find a pendingBlockToMove, iteration +1
+          // source node cannot find a pending block to move, iteration +1
-          noPendingBlockIteration++;
+          noPendingMoveIteration++;
           // in case no blocks can be moved for source node's task,
           // jump out of while-loop after 5 iterations.
-          if (noPendingBlockIteration >= MAX_NO_PENDING_MOVE_ITERATIONS) {
+          if (noPendingMoveIteration >= MAX_NO_PENDING_MOVE_ITERATIONS) {
             resetScheduledSize();
           }
         }
@@ -726,29 +710,19 @@ public class Dispatcher {
     }
   }
 
-  Dispatcher(NameNodeConnector theblockpool, Set<String> includedNodes,
+  public Dispatcher(NameNodeConnector nnc, Set<String> includedNodes,
-      Set<String> excludedNodes, Configuration conf) {
+      Set<String> excludedNodes, long movedWinWidth, int moverThreads,
-    this.nnc = theblockpool;
+      int dispatcherThreads, int maxConcurrentMovesPerNode, Configuration conf) {
-    this.keyManager = nnc.getKeyManager();
+    this.nnc = nnc;
     this.excludedNodes = excludedNodes;
     this.includedNodes = includedNodes;
-
+    this.movedBlocks = new MovedBlocks<StorageGroup>(movedWinWidth);
-    final long movedWinWidth = conf.getLong(
-        DFSConfigKeys.DFS_BALANCER_MOVEDWINWIDTH_KEY,
-        DFSConfigKeys.DFS_BALANCER_MOVEDWINWIDTH_DEFAULT);
-    movedBlocks = new MovedBlocks<BalancerDatanode.StorageGroup>(movedWinWidth);
 
     this.cluster = NetworkTopology.getInstance(conf);
 
-    this.moveExecutor = Executors.newFixedThreadPool(conf.getInt(
+    this.moveExecutor = Executors.newFixedThreadPool(moverThreads);
-        DFSConfigKeys.DFS_BALANCER_MOVERTHREADS_KEY,
+    this.dispatchExecutor = Executors.newFixedThreadPool(dispatcherThreads);
-        DFSConfigKeys.DFS_BALANCER_MOVERTHREADS_DEFAULT));
+    this.maxConcurrentMovesPerNode = maxConcurrentMovesPerNode;
-    this.dispatchExecutor = Executors.newFixedThreadPool(conf.getInt(
-        DFSConfigKeys.DFS_BALANCER_DISPATCHERTHREADS_KEY,
-        DFSConfigKeys.DFS_BALANCER_DISPATCHERTHREADS_DEFAULT));
-    this.maxConcurrentMovesPerNode = conf.getInt(
-        DFSConfigKeys.DFS_DATANODE_BALANCE_MAX_NUM_CONCURRENT_MOVES_KEY,
-        DFSConfigKeys.DFS_DATANODE_BALANCE_MAX_NUM_CONCURRENT_MOVES_DEFAULT);
 
     final boolean fallbackToSimpleAuthAllowed = conf.getBoolean(
         CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY,
@@ -784,7 +758,7 @@ public class Dispatcher {
     return b;
   }
 
-  void add(Source source, BalancerDatanode.StorageGroup target) {
+  void add(Source source, StorageGroup target) {
     sources.add(source);
     targets.add(target);
   }
@@ -826,8 +800,8 @@ public class Dispatcher {
     return trimmed;
   }
 
-  public BalancerDatanode newDatanode(DatanodeStorageReport r) {
+  public DDatanode newDatanode(DatanodeStorageReport r) {
-    return new BalancerDatanode(r, maxConcurrentMovesPerNode);
+    return new DDatanode(r, maxConcurrentMovesPerNode);
   }
 
   public boolean dispatchAndCheckContinue() throws InterruptedException {
@@ -884,8 +858,8 @@ public class Dispatcher {
   private void waitForMoveCompletion() {
     for(;;) {
       boolean empty = true;
-      for (BalancerDatanode.StorageGroup t : targets) {
+      for (StorageGroup t : targets) {
-        if (!t.getBalancerDatanode().isPendingQEmpty()) {
+        if (!t.getDDatanode().isPendingQEmpty()) {
           empty = false;
           break;
         }
@@ -907,8 +881,8 @@ public class Dispatcher {
    * 2. the block does not have a replica on the target;
    * 3. doing the move does not reduce the number of racks that the block has
    */
-  private boolean isGoodBlockCandidate(Source source,
+  private boolean isGoodBlockCandidate(Source source, StorageGroup target,
-      BalancerDatanode.StorageGroup target, DBlock block) {
+      DBlock block) {
     if (source.storageType != target.storageType) {
       return false;
     }
@@ -933,17 +907,17 @@ public class Dispatcher {
    * Determine whether moving the given block replica from source to target
    * would reduce the number of racks of the block replicas.
    */
-  private boolean reduceNumOfRacks(Source source,
+  private boolean reduceNumOfRacks(Source source, StorageGroup target,
-      BalancerDatanode.StorageGroup target, DBlock block) {
+      DBlock block) {
-    final DatanodeInfo sourceDn = source.getDatanode();
+    final DatanodeInfo sourceDn = source.getDatanodeInfo();
-    if (cluster.isOnSameRack(sourceDn, target.getDatanode())) {
+    if (cluster.isOnSameRack(sourceDn, target.getDatanodeInfo())) {
       // source and target are on the same rack
       return false;
     }
     boolean notOnSameRack = true;
     synchronized (block) {
-      for (BalancerDatanode.StorageGroup loc : block.getLocations()) {
+      for (StorageGroup loc : block.getLocations()) {
-        if (cluster.isOnSameRack(loc.getDatanode(), target.getDatanode())) {
+        if (cluster.isOnSameRack(loc.getDatanodeInfo(), target.getDatanodeInfo())) {
           notOnSameRack = false;
           break;
         }
@@ -953,8 +927,8 @@ public class Dispatcher {
       // target is not on the same rack as any replica
       return false;
     }
-    for (BalancerDatanode.StorageGroup g : block.getLocations()) {
+    for (StorageGroup g : block.getLocations()) {
-      if (g != source && cluster.isOnSameRack(g.getDatanode(), sourceDn)) {
+      if (g != source && cluster.isOnSameRack(g.getDatanodeInfo(), sourceDn)) {
         // source is on the same rack of another replica
         return false;
       }
@@ -971,10 +945,10 @@ public class Dispatcher {
    *         group with target
    */
   private boolean isOnSameNodeGroupWithReplicas(
-      BalancerDatanode.StorageGroup target, DBlock block, Source source) {
+      StorageGroup target, DBlock block, Source source) {
-    final DatanodeInfo targetDn = target.getDatanode();
+    final DatanodeInfo targetDn = target.getDatanodeInfo();
-    for (BalancerDatanode.StorageGroup g : block.getLocations()) {
+    for (StorageGroup g : block.getLocations()) {
-      if (g != source && cluster.isOnSameNodeGroup(g.getDatanode(), targetDn)) {
+      if (g != source && cluster.isOnSameNodeGroup(g.getDatanodeInfo(), targetDn)) {
         return true;
       }
     }

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

@@ -0,0 +1,44 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.balancer;
+
+/**
+ * Exit status - The values associated with each exit status is directly mapped
+ * to the process's exit code in command line.
+ */
+public enum ExitStatus {
+  SUCCESS(0),
+  IN_PROGRESS(1),
+  ALREADY_RUNNING(-1),
+  NO_MOVE_BLOCK(-2),
+  NO_MOVE_PROGRESS(-3),
+  IO_EXCEPTION(-4),
+  ILLEGAL_ARGUMENTS(-5),
+  INTERRUPTED(-6);
+
+  private final int code;
+
+  private ExitStatus(int code) {
+    this.code = code;
+  }
+  
+  /** @return the command line exit code. */
+  public int getExitCode() {
+    return code;
+  }
+}

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

@@ -570,10 +570,10 @@ public class TestBalancer {
     final int r = Balancer.run(namenodes, p, conf);
     if (conf.getInt(DFSConfigKeys.DFS_DATANODE_BALANCE_MAX_NUM_CONCURRENT_MOVES_KEY, 
         DFSConfigKeys.DFS_DATANODE_BALANCE_MAX_NUM_CONCURRENT_MOVES_DEFAULT) ==0) {
-      assertEquals(Balancer.ReturnStatus.NO_MOVE_PROGRESS.code, r);
+      assertEquals(ExitStatus.NO_MOVE_PROGRESS.getExitCode(), r);
       return;
     } else {
-      assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
+      assertEquals(ExitStatus.SUCCESS.getExitCode(), r);
     }
     waitForHeartBeat(totalUsedSpace, totalCapacity, client, cluster);
     LOG.info("Rebalancing with default ctor.");
@@ -717,7 +717,7 @@ public class TestBalancer {
           Balancer.Parameters.DEFAULT.threshold,
           datanodes, Balancer.Parameters.DEFAULT.nodesToBeIncluded);
       final int r = Balancer.run(namenodes, p, conf);
-      assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
+      assertEquals(ExitStatus.SUCCESS.getExitCode(), r);
     } finally {
       cluster.shutdown();
     }

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

@@ -98,7 +98,7 @@ public class TestBalancerWithHANameNodes {
       assertEquals(1, namenodes.size());
       assertTrue(namenodes.contains(HATestUtil.getLogicalUri(cluster)));
       final int r = Balancer.run(namenodes, Balancer.Parameters.DEFAULT, conf);
-      assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
+      assertEquals(ExitStatus.SUCCESS.getExitCode(), r);
       TestBalancer.waitForBalancer(totalUsedSpace, totalCapacity, client,
           cluster, Balancer.Parameters.DEFAULT);
     } finally {

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

@@ -160,7 +160,7 @@ public class TestBalancerWithMultipleNameNodes {
     // start rebalancing
     final Collection<URI> namenodes = DFSUtil.getNsServiceRpcUris(s.conf);
     final int r = Balancer.run(namenodes, Balancer.Parameters.DEFAULT, s.conf);
-    Assert.assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
+    Assert.assertEquals(ExitStatus.SUCCESS.getExitCode(), r);
 
     LOG.info("BALANCER 2");
     wait(s.clients, totalUsed, totalCapacity);

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

@@ -176,7 +176,7 @@ public class TestBalancerWithNodeGroup {
     // start rebalancing
     Collection<URI> namenodes = DFSUtil.getNsServiceRpcUris(conf);
     final int r = Balancer.run(namenodes, Balancer.Parameters.DEFAULT, conf);
-    assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
+    assertEquals(ExitStatus.SUCCESS.getExitCode(), r);
 
     waitForHeartBeat(totalUsedSpace, totalCapacity);
     LOG.info("Rebalancing with default factor.");
@@ -190,8 +190,8 @@ public class TestBalancerWithNodeGroup {
     // start rebalancing
     Collection<URI> namenodes = DFSUtil.getNsServiceRpcUris(conf);
     final int r = Balancer.run(namenodes, Balancer.Parameters.DEFAULT, conf);
-    Assert.assertTrue(r == Balancer.ReturnStatus.SUCCESS.code ||
+    Assert.assertTrue(r == ExitStatus.SUCCESS.getExitCode() ||
-        (r == Balancer.ReturnStatus.NO_MOVE_PROGRESS.code));
+        (r == ExitStatus.NO_MOVE_PROGRESS.getExitCode()));
     waitForHeartBeat(totalUsedSpace, totalCapacity);
     LOG.info("Rebalancing with default factor.");
   }