HDFS-14449. Expose total number of DT in JMX for Namenode. Contributed by Fengnan Li.

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/metrics/NamenodeBeanMetrics.java

@@ -838,6 +838,11 @@ public class NamenodeBeanMetrics
     return null;
   }
 
+  @Override
+  public long getCurrentTokensCount() {
+    return 0;
+  }
+
   private Router getRouter() throws IOException {
     if (this.router == null) {
       throw new IOException("Router is not initialized");

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -4423,6 +4423,13 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     return dir.ezManager.getNumEncryptionZones();
   }
 
+  @Override // FSNamesystemMBean
+  @Metric({ "CurrentTokensCount", "The number of delegation tokens"})
+  public long getCurrentTokensCount() {
+    return dtSecretManager != null ?
+        dtSecretManager.getCurrentTokensSize() : -1;
+  }
+
   /**
    * Returns the length of the wait Queue for the FSNameSystemLock.
    *

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/FSNamesystemMBean.java

@@ -242,4 +242,10 @@ public interface FSNamesystemMBean {
    * @return Number of ENTERING_MAINTENANCE data nodes
    */
   int getNumEnteringMaintenanceDataNodes();
+
+  /**
+   * Get the current number of delegation tokens in memory.
+   * @return number of DTs
+   */
+  long getCurrentTokensCount();
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/security/TestDelegationToken.java

@@ -20,6 +20,7 @@ package org.apache.hadoop.hdfs.security;
 
 
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
@@ -41,6 +42,7 @@ import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenSecretManager;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.StartupOption;
+import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.namenode.NameNodeAdapter;
 import org.apache.hadoop.hdfs.server.namenode.web.resources.NamenodeWebHdfsMethods;
@@ -154,6 +156,26 @@ public class TestDelegationToken {
     }
   }
 
+  @Test
+  public void testDelegationTokenMetrics() throws Exception {
+    FSNamesystem namesystem = cluster.getNamesystem();
+    // should start with no token
+    assertEquals(0, namesystem.getCurrentTokensCount());
+
+    // get token
+    Token<DelegationTokenIdentifier> token = generateDelegationToken(
+        "SomeUser", "JobTracker");
+    assertEquals(1, namesystem.getCurrentTokensCount());
+
+    // Renew token shouldn't change the count of tokens
+    dtSecretManager.renewToken(token, "JobTracker");
+    assertEquals(1, namesystem.getCurrentTokensCount());
+
+    // Cancel token should remove the token from memory
+    dtSecretManager.cancelToken(token, "JobTracker");
+    assertEquals(0, namesystem.getCurrentTokensCount());
+  }
+
   @Test
   public void testAddDelegationTokensDFSApi() throws Exception {
     UserGroupInformation ugi = UserGroupInformation.createRemoteUser("JobTracker");