HADOOP-17995. Stale record should be remove when DataNodePeerMetrics#dumpSendPacketDownstreamAvgInfoAsJson (#3630)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableRollingAverages.java

@@ -179,8 +179,11 @@ public class MutableRollingAverages extends MutableMetric implements Closeable {
         long totalCount = 0;
 
         for (final SumAndCount sumAndCount : entry.getValue()) {
-          totalCount += sumAndCount.getCount();
-          totalSum += sumAndCount.getSum();
+          if (Time.monotonicNow() - sumAndCount.getSnapshotTimeStamp()
+              < recordValidityMs) {
+            totalCount += sumAndCount.getCount();
+            totalSum += sumAndCount.getSum();
+          }
         }
 
         if (totalCount != 0) {

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

@@ -122,10 +122,16 @@ public class TestDataNodePeerMetrics {
     GenericTestUtils.waitFor(
         () -> rollingAverages.getStats(numSamples).size() > 0, 500, 5000);
     assertEquals(3, rollingAverages.getStats(numSamples).size());
+    String json = peerMetrics.dumpSendPacketDownstreamAvgInfoAsJson();
+    for (String peerAddr : peerAddrList) {
+      assertThat(json, containsString(peerAddr));
+    }
     /* wait for stale report to be removed */
     GenericTestUtils.waitFor(
         () -> rollingAverages.getStats(numSamples).isEmpty(), 500, 10000);
     assertEquals(0, rollingAverages.getStats(numSamples).size());
+    json = peerMetrics.dumpSendPacketDownstreamAvgInfoAsJson();
+    assertEquals("{}", json);
 
     /* dn can report peer metrics normally when it added back to cluster */
     for (String peerAddr : peerAddrList) {
@@ -138,6 +144,10 @@ public class TestDataNodePeerMetrics {
     GenericTestUtils.waitFor(
         () -> rollingAverages.getStats(numSamples).size() > 0, 500, 10000);
     assertEquals(3, rollingAverages.getStats(numSamples).size());
+    json = peerMetrics.dumpSendPacketDownstreamAvgInfoAsJson();
+    for (String peerAddr : peerAddrList) {
+      assertThat(json, containsString(peerAddr));
+    }
   }
 
   /**