HDFS-12247. Ozone: KeySpaceManager should unregister KSMMetrics upon stop. Contributed by Yiqun Lin.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/ksm/KSMMetrics.java

@@ -32,6 +32,9 @@ import org.apache.hadoop.metrics2.lib.MutableCounterLong;
 @InterfaceAudience.Private
 @Metrics(about="Key Space Manager Metrics", context="dfs")
 public class KSMMetrics {
+  private static final String SOURCE_NAME =
+      KSMMetrics.class.getSimpleName();
+
   // KSM request type op metrics
   private @Metric MutableCounterLong numVolumeOps;
   private @Metric MutableCounterLong numBucketOps;
@@ -76,7 +79,7 @@ public class KSMMetrics {
 
   public static KSMMetrics create() {
     MetricsSystem ms = DefaultMetricsSystem.instance();
-    return ms.register("KSMMetrics",
+    return ms.register(SOURCE_NAME,
         "Key Space Manager Metrics",
         new KSMMetrics());
   }
@@ -365,4 +368,9 @@ public class KSMMetrics {
   public long getNumVolumeListFails() {
     return numVolumeListFails.value();
   }
+
+  public void unRegister() {
+    MetricsSystem ms = DefaultMetricsSystem.instance();
+    ms.unregisterSource(SOURCE_NAME);
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/ksm/KeySpaceManager.java

@@ -229,6 +229,7 @@ public class KeySpaceManager extends ServiceRuntimeInfo
       ksmRpcServer.stop();
       metadataManager.stop();
       httpServer.stop();
+      metrics.unRegister();
       unregisterMXBean();
     } catch (Exception e) {
       LOG.error("Key Space Manager stop failed.", e);