From 0182ea16d359b41c065bf9cbf740f8b23f6381e3 Mon Sep 17 00:00:00 2001
From: Tsz-wo Sze <szetszwo@apache.org>
Date: Thu, 15 Aug 2013 04:52:52 +0000
Subject: [PATCH] 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       |  3 +++
 .../BlockPlacementPolicyWithNodeGroup.java        | 15 ++++++++-------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 4d62131b8cb..9b50809b47a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/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
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyWithNodeGroup.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyWithNodeGroup.java
index 643d2b401cd..e98318b9783 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyWithNodeGroup.java
+++ b/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);
     }
   }