HDFS-9072. Fix random failures in TestJMXGet. (J.Andreina via stevel)

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

@@ -1352,6 +1352,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-9067. o.a.h.hdfs.server.datanode.fsdataset.impl.TestLazyWriter
     is failing in trunk (Surendra Singh Lilhore via vinayakumarb)
 
+    HDFS-9072. Fix random failures in TestJMXGet.
+    (J.Andreina via stevel)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/tools/TestJMXGet.java

@@ -103,10 +103,12 @@ public class TestJMXGet {
     assertTrue("error printAllValues", checkPrintAllValues(jmx));
 
     //get some data from different source
+    DFSTestUtil.waitForMetric(jmx, "NumLiveDataNodes", numDatanodes);
     assertEquals(numDatanodes, Integer.parseInt(
         jmx.getValue("NumLiveDataNodes")));
     assertGauge("CorruptBlocks", Long.parseLong(jmx.getValue("CorruptBlocks")),
                 getMetrics("FSNamesystem"));
+    DFSTestUtil.waitForMetric(jmx, "NumOpenConnections", numDatanodes);
     assertEquals(numDatanodes, Integer.parseInt(
         jmx.getValue("NumOpenConnections")));
 
@@ -151,6 +153,7 @@ public class TestJMXGet {
     String serviceName = "DataNode";
     jmx.setService(serviceName);
     jmx.init();
+    DFSTestUtil.waitForMetric(jmx, "BytesWritten", fileSize);
     assertEquals(fileSize, Integer.parseInt(jmx.getValue("BytesWritten")));
 
     cluster.shutdown();