HDFS-4898. BlockPlacementPolicyWithNodeGroup.chooseRemoteRack() fails to properly fallback to local rack. (szetszwo)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1514159 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -126,6 +126,9 @@ Release 1.3.0 - unreleased
     MAPREDUCE-5367. Local jobs all use same local working directory
     (Sandy Ryza)
 
+    HDFS-4898. BlockPlacementPolicyWithNodeGroup.chooseRemoteRack() fails to
+    properly fallback to local rack. (szetszwo)
+
 Release 1.2.2 - unreleased
 
   INCOMPATIBLE CHANGES

src/hdfs/org/apache/hadoop/hdfs/server/namenode/BlockPlacementPolicyWithNodeGroup.java

@@ -169,16 +169,17 @@ public class BlockPlacementPolicyWithNodeGroup extends BlockPlacementPolicyDefau
       long blocksize, int maxReplicasPerRack, List<DatanodeDescriptor> results,
       boolean avoidStaleNodes) throws NotEnoughReplicasException {
     int oldNumOfReplicas = results.size();
-    // randomly choose one node from remote racks
+
+    final String rackLocation = NetworkTopology.getFirstHalf(
+        localMachine.getNetworkLocation());
     try {
-      chooseRandom(
-          numOfReplicas,
-          "~" + NetworkTopology.getFirstHalf(localMachine.getNetworkLocation()),
-          excludedNodes, blocksize, maxReplicasPerRack, results,
-          avoidStaleNodes);
+      // randomly choose from remote racks
+      chooseRandom(numOfReplicas, "~" + rackLocation, excludedNodes, blocksize,
+          maxReplicasPerRack, results, avoidStaleNodes);
     } catch (NotEnoughReplicasException e) {
+      // fall back to the local rack
       chooseRandom(numOfReplicas - (results.size() - oldNumOfReplicas),
-          localMachine.getNetworkLocation(), excludedNodes, blocksize,
+          rackLocation, excludedNodes, blocksize,
           maxReplicasPerRack, results, avoidStaleNodes);
     }
   }