MAPREDUCE-5155. Race condition in test case TestFetchFailure cause it to fail (Contributed by Haibo Chen via Daniel Templeton)

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestFetchFailure.java

@@ -24,6 +24,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Iterator;
 
+import com.google.common.base.Supplier;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.mapred.TaskCompletionEvent;
 import org.apache.hadoop.mapreduce.Counters;
@@ -45,6 +46,7 @@ import org.apache.hadoop.mapreduce.v2.app.job.event.JobTaskAttemptFetchFailureEv
 import org.apache.hadoop.mapreduce.v2.app.job.event.TaskAttemptEvent;
 import org.apache.hadoop.mapreduce.v2.app.job.event.TaskAttemptEventType;
 import org.apache.hadoop.mapreduce.v2.app.job.event.TaskAttemptStatusUpdateEvent;
+import org.apache.hadoop.test.GenericTestUtils;
 import org.apache.hadoop.yarn.event.EventHandler;
 import org.junit.Assert;
 import org.junit.Test;
@@ -79,8 +81,19 @@ public class TestFetchFailure {
     
     // wait for map success
     app.waitForState(mapTask, TaskState.SUCCEEDED);
-    
-    TaskAttemptCompletionEvent[] events = 
+
+    final int checkIntervalMillis = 10;
+    final int waitForMillis = 800;
+    GenericTestUtils.waitFor(new Supplier<Boolean>() {
+      @Override
+      public Boolean get() {
+        TaskAttemptCompletionEvent[] events = job
+            .getTaskAttemptCompletionEvents(0, 100);
+        return events.length >= 1;
+      }
+    }, checkIntervalMillis, waitForMillis);
+
+    TaskAttemptCompletionEvent[] events =
       job.getTaskAttemptCompletionEvents(0, 100);
     Assert.assertEquals("Num completion events not correct",
         1, events.length);