[GitHub] [hadoop] haiyang1987 commented on a change in pull request #3630: HADOOP-17995. Stale record should be remove when DataNodePeerMetrics#dumpSendPacketDownstreamAvgInfoAsJson

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haiyang1987 commented on a change in pull request #3630:
URL: https://github.com/apache/hadoop/pull/3630#discussion_r746505180



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File path: hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableRollingAverages.java
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@@ -167,7 +167,7 @@ synchronized void replaceScheduledTask(int windows, long interval,
   }
 
   @Override
-  public void snapshot(MetricsRecordBuilder builder, boolean all) {
+  public synchronized void snapshot(MetricsRecordBuilder builder, boolean all) {

Review comment:
       @ferhui @tomscut Thanks your comment.
   
   
   SpotBugs | module:hadoop-common-project/hadoop-common
   -- | --
     | Inconsistent synchronization of org.apache.hadoop.metrics2.lib.MutableRollingAverages.recordValidityMs; locked 66% of time Unsynchronized access at MutableRollingAverages.java:66% of time Unsynchronized access at MutableRollingAverages.java:[line 182]
   
   So consider add synchronized.
   Reference code MutableRatesWithAggregation#snapshot, the  method to add the synchronized
   
   > public class MutableRatesWithAggregation extends MutableMetric {
   > @Override
   >   public synchronized void snapshot(MetricsRecordBuilder rb, boolean all) {
   >     Iterator<WeakReference<ConcurrentMap<String, ThreadSafeSampleStat>>> iter =
   >         weakReferenceQueue.iterator();
   >     ...
   >   }
   > }
   




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