From 8deced0073aedb4526dcdab7b65ee06cf2a26019 Mon Sep 17 00:00:00 2001
From: Ayush Saxena <ayushsaxena@apache.org>
Date: Tue, 30 Jul 2019 22:17:39 +0530
Subject: [PATCH] HDFS-14677.
 TestDataNodeHotSwapVolumes#testAddVolumesConcurrently fails intermittently in
 trunk. Contributed by Chen Zhang.

---
 .../hdfs/server/datanode/TestDataNodeHotSwapVolumes.java       | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
index e72c499624d..d98047f47fa 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
@@ -549,7 +549,8 @@ public class TestDataNodeHotSwapVolumes {
     dn.data = Mockito.spy(data);
 
     final int newVolumeCount = 40;
-    List<Thread> addVolumeDelayedThreads = new ArrayList<>();
+    List<Thread> addVolumeDelayedThreads =
+        Collections.synchronizedList(new ArrayList<>());
     AtomicBoolean addVolumeError = new AtomicBoolean(false);
     AtomicBoolean listStorageError = new AtomicBoolean(false);
     CountDownLatch addVolumeCompletionLatch =