HDFS-8721. Add a metric for number of encryption zones. Contributed by Rakesh R.

(cherry picked from commit cb03768b1b2250b9b5a7944cf6ef918e8a974e20)
(cherry picked from commit 57d55d40dd41ba4449b91c4676131b6b840052c4)

hadoop-common-project/hadoop-common/src/site/markdown/Metrics.md

@@ -215,6 +215,7 @@ Each metrics record contains tags such as HAState and Hostname as additional inf
 | `TotalLoad` | Current number of connections |
 | `SnapshottableDirectories` | Current number of snapshottable directories |
 | `Snapshots` | Current number of snapshots |
+| `NumEncryptionZones` | Current number of encryption zones |
 | `BlocksTotal` | Current number of allocated blocks in the system |
 | `FilesTotal` | Current number of files and directories |
 | `PendingReplicationBlocks` | Current number of blocks pending to be replicated |

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

@@ -386,6 +386,13 @@ public class EncryptionZoneManager {
     return new BatchedListEntries<EncryptionZone>(zones, hasMore);
   }
 
+  /**
+   * @return number of encryption zones.
+   */
+  public int getNumEncryptionZones() {
+    return encryptionZones.size();
+  }
+
   /**
    * @return Whether there has been any attempt to create an encryption zone in
    * the cluster at all. If not, it is safe to quickly return null when

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

@@ -4930,6 +4930,12 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     return JSON.toString(info);
   }
 
+  @Override // FSNamesystemMBean
+  @Metric({ "NumEncryptionZones", "The number of encryption zones" })
+  public int getNumEncryptionZones() {
+    return dir.ezManager.getNumEncryptionZones();
+  }
+
   int getNumberOfDatanodes(DatanodeReportType type) {
     readLock();
     try {

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

@@ -184,4 +184,9 @@ public interface FSNamesystemMBean {
    * @return JSON string
    */
   public String getTopUserOpCounts();
+
+  /**
+   * Return the number of encryption zones in the system.
+   */
+  int getNumEncryptionZones();
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestEncryptionZones.java

@@ -100,6 +100,8 @@ import static org.mockito.Mockito.any;
 import static org.mockito.Mockito.anyString;
 import static org.apache.hadoop.hdfs.DFSTestUtil.verifyFilesEqual;
 import static org.apache.hadoop.test.GenericTestUtils.assertExceptionContains;
+import static org.apache.hadoop.test.MetricsAsserts.assertGauge;
+import static org.apache.hadoop.test.MetricsAsserts.getMetrics;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotEquals;
@@ -123,6 +125,7 @@ public class TestEncryptionZones {
   protected DistributedFileSystem fs;
   private File testRootDir;
   protected final String TEST_KEY = "test_key";
+  private static final String NS_METRICS = "FSNamesystem";
 
   protected FileSystemTestWrapper fsWrapper;
   protected FileContextTestWrapper fcWrapper;
@@ -361,6 +364,9 @@ public class TestEncryptionZones {
     fs.setSafeMode(SafeModeAction.SAFEMODE_LEAVE);
     cluster.restartNameNode(true);
     assertNumZones(numZones);
+    assertEquals("Unexpected number of encryption zones!", numZones, cluster
+        .getNamesystem().getNumEncryptionZones());
+    assertGauge("NumEncryptionZones", numZones, getMetrics(NS_METRICS));
     assertZonePresent(null, zone1.toString());
 
     // Verify newly added ez is present after restarting the NameNode

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSNamesystemMBean.java

@@ -117,6 +117,11 @@ public class TestFSNamesystemMBean {
         "PendingDeletionBlocks");
       assertNotNull(pendingDeletionBlocks);
       assertTrue(pendingDeletionBlocks instanceof Long);
+
+      Object encryptionZones = mbs.getAttribute(mxbeanName,
+          "NumEncryptionZones");
+      assertNotNull(encryptionZones);
+      assertTrue(encryptionZones instanceof Integer);
     } finally {
       if (cluster != null) {
         cluster.shutdown();