From d55f3780fbf9308554ef3362c2be89651db43f46 Mon Sep 17 00:00:00 2001
From: Arun Murthy <acmurthy@apache.org>
Date: Sat, 5 Oct 2013 22:20:18 +0000
Subject: [PATCH] YARN-1032. Fixed NPE in RackResolver. Contributed by Lohit
 Vijayarenu.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1529534 13f79535-47bb-0310-9956-ffa450edef68
---
 hadoop-yarn-project/CHANGES.txt                      |  2 ++
 .../org/apache/hadoop/yarn/util/RackResolver.java    | 12 ++++++++++--
 .../apache/hadoop/yarn/util/TestRackResolver.java    | 10 ++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/hadoop-yarn-project/CHANGES.txt b/hadoop-yarn-project/CHANGES.txt
index 6e8ad1edbd9..0c3a0307fbf 100644
--- a/hadoop-yarn-project/CHANGES.txt
+++ b/hadoop-yarn-project/CHANGES.txt
@@ -179,6 +179,8 @@ Release 2.1.2 - UNRELEASED
     YARN-1273. Fixed Distributed-shell to account for containers that failed
     to start. (Hitesh Shah via vinodkv)
 
+    YARN-1032. Fixed NPE in RackResolver. (Lohit Vijayarenu via acmurthy)
+
 Release 2.1.1-beta - 2013-09-23
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/RackResolver.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/RackResolver.java
index 601f8abc08e..cc2a56c3be6 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/RackResolver.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/RackResolver.java
@@ -29,6 +29,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
 import org.apache.hadoop.net.CachedDNSToSwitchMapping;
 import org.apache.hadoop.net.DNSToSwitchMapping;
+import org.apache.hadoop.net.NetworkTopology;
 import org.apache.hadoop.net.Node;
 import org.apache.hadoop.net.NodeBase;
 import org.apache.hadoop.net.ScriptBasedMapping;
@@ -98,8 +99,15 @@ public class RackResolver {
     List <String> tmpList = new ArrayList<String>(1);
     tmpList.add(hostName);
     List <String> rNameList = dnsToSwitchMapping.resolve(tmpList);
-    String rName = rNameList.get(0);
-    LOG.info("Resolved " + hostName + " to " + rName);
+    String rName = null;
+    if (rNameList == null || rNameList.get(0) == null) {
+      rName = NetworkTopology.DEFAULT_RACK;
+      LOG.info("Couldn't resolve " + hostName + ". Falling back to "
+          + NetworkTopology.DEFAULT_RACK);
+    } else {
+      rName = rNameList.get(0);
+      LOG.info("Resolved " + hostName + " to " + rName);
+    }
     return new NodeBase(hostName, rName);
   }
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestRackResolver.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestRackResolver.java
index 42f7b9b5091..70ca23c3a2e 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestRackResolver.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestRackResolver.java
@@ -28,6 +28,7 @@ import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
 import org.apache.hadoop.net.DNSToSwitchMapping;
+import org.apache.hadoop.net.NetworkTopology;
 import org.apache.hadoop.net.Node;
 import org.junit.Assert;
 import org.junit.Test;
@@ -35,6 +36,8 @@ import org.junit.Test;
 public class TestRackResolver {
 
   private static Log LOG = LogFactory.getLog(TestRackResolver.class);
+  private static final String invalidHost = "invalidHost";
+
 
   public static final class MyResolver implements DNSToSwitchMapping {
 
@@ -50,6 +53,11 @@ public class TestRackResolver {
       if (hostList.isEmpty()) {
         return returnList;
       }
+      if (hostList.get(0).equals(invalidHost)) {
+        // Simulate condition where resolving host returns null
+        return null; 
+      }
+        
       LOG.info("Received resolve request for "
           + hostList.get(0));
       if (hostList.get(0).equals("host1")
@@ -90,6 +98,8 @@ public class TestRackResolver {
     Assert.assertEquals("/rack1", node.getNetworkLocation());
     node = RackResolver.resolve("host1");
     Assert.assertEquals("/rack1", node.getNetworkLocation());
+    node = RackResolver.resolve(invalidHost);
+    Assert.assertEquals(NetworkTopology.DEFAULT_RACK, node.getNetworkLocation());
   }
 
 }