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

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1514156 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -324,6 +324,9 @@ Release 2.1.1-beta - UNRELEASED
     HDFS-5051. nn fails to download checkpointed image from snn in some
     setups. (Vinay and suresh via suresh)
 
+    HDFS-4898. BlockPlacementPolicyWithNodeGroup.chooseRemoteRack() fails to
+    properly fallback to local rack. (szetszwo)
+
 Release 2.1.0-beta - 2013-08-06
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/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);
     }
   }