From ec21ce425f4e5637be716406f9d0e038921550d7 Mon Sep 17 00:00:00 2001
From: Arpit Agarwal <arp@apache.org>
Date: Tue, 16 May 2017 19:51:04 -0700
Subject: [PATCH] HDFS-11827. NPE is thrown when log level changed in
 BlockPlacementPolicyDefault#chooseRandom() method. Contributed by xupeng.

---
 .../server/blockmanagement/BlockPlacementPolicyDefault.java   | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyDefault.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyDefault.java
index a245f0c006..a47939726a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyDefault.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyDefault.java
@@ -735,7 +735,7 @@ protected DatanodeStorageInfo chooseRandom(int numOfReplicas,
       }
       Preconditions.checkState(excludedNodes.add(chosenNode), "chosenNode "
           + chosenNode + " is already in excludedNodes " + excludedNodes);
-      if (LOG.isDebugEnabled()) {
+      if (LOG.isDebugEnabled() && builder != null) {
         builder.append("\nNode ").append(NodeBase.getPath(chosenNode))
             .append(" [");
       }
@@ -771,7 +771,7 @@ protected DatanodeStorageInfo chooseRandom(int numOfReplicas,
           }
         }
 
-        if (LOG.isDebugEnabled()) {
+        if (LOG.isDebugEnabled() && builder != null) {
           builder.append("\n]");
         }