HDFS-6078. Merging r1575561 from branch-2 to branch-2.4.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1575562 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -318,6 +318,8 @@ Release 2.4.0 - UNRELEASED
     HDFS-5064. Standby checkpoints should not block concurrent readers.
     (atm via wang)
 
+    HDFS-6078. TestIncrementalBlockReports is flaky. (Arpit Agarwal)
+
   BREAKDOWN OF HDFS-5698 SUBTASKS AND RELATED JIRAS
 
     HDFS-5717. Save FSImage header in protobuf. (Haohui Mai via jing9)

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestIncrementalBlockReports.java

@@ -20,6 +20,7 @@ package org.apache.hadoop.hdfs.server.datanode;
 import static junit.framework.Assert.assertFalse;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.atLeastOnce;
 import static org.mockito.Mockito.times;
 
 import java.io.IOException;
@@ -195,7 +196,7 @@ public class TestIncrementalBlockReports {
       Thread.sleep(2000);
 
       // Ensure that the received block is reported.
-      Mockito.verify(nnSpy, times(1)).blockReceivedAndDeleted(
+      Mockito.verify(nnSpy, atLeastOnce()).blockReceivedAndDeleted(
           any(DatanodeRegistration.class),
           anyString(),
           any(StorageReceivedDeletedBlocks[].class));