HDFS-8211. DataNode UUID is always null in the JMX counter. (Contributed by Anu Engineer)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -560,6 +560,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8191. Fix byte to integer casting in SimulatedFSDataset#simulatedByte.
     (Zhe Zhang via wang)
 
+    HDFS-8211. DataNode UUID is always null in the JMX counter. (Anu Engineer
+    via Arpit Agarwal)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java

@@ -1226,7 +1226,7 @@ public class DataNode extends ReconfigurableBase
    *
    * @throws IOException
    */
-  private synchronized void checkDatanodeUuid() throws IOException {
+  synchronized void checkDatanodeUuid() throws IOException {
     if (storage.getDatanodeUuid() == null) {
       storage.setDatanodeUuid(generateUuid());
       storage.writeAll();
@@ -3159,7 +3159,7 @@ public class DataNode extends ReconfigurableBase
   }
 
   public String getDatanodeUuid() {
-    return id == null ? null : id.getDatanodeUuid();
+    return storage == null ? null : storage.getDatanodeUuid();
   }
 
   boolean shouldRun() {

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

@@ -0,0 +1,65 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hdfs.server.datanode;
+
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.junit.Test;
+
+import java.net.InetSocketAddress;
+import java.util.ArrayList;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class TestDataNodeUUID {
+
+  /**
+   * This test makes sure that we have a valid
+   * Node ID after the checkNodeUUID is done.
+   */
+  @Test
+  public void testDatanodeUuid() throws Exception {
+
+    final InetSocketAddress NN_ADDR = new InetSocketAddress(
+      "localhost", 5020);
+    Configuration conf = new HdfsConfiguration();
+    conf.set(DFSConfigKeys.DFS_DATANODE_ADDRESS_KEY, "0.0.0.0:0");
+    conf.set(DFSConfigKeys.DFS_DATANODE_HTTP_ADDRESS_KEY, "0.0.0.0:0");
+    conf.set(DFSConfigKeys.DFS_DATANODE_IPC_ADDRESS_KEY, "0.0.0.0:0");
+    FileSystem.setDefaultUri(conf,
+      "hdfs://" + NN_ADDR.getHostName() + ":" + NN_ADDR.getPort());
+    ArrayList<StorageLocation> locations = new ArrayList<>();
+
+    DataNode dn = new DataNode(conf, locations, null);
+
+    //Assert that Node iD is null
+    String nullString = null;
+    assertEquals(dn.getDatanodeUuid(), nullString);
+
+    // CheckDataNodeUUID will create an UUID if UUID is null
+    dn.checkDatanodeUuid();
+
+    // Make sure that we have a valid DataNodeUUID at that point of time.
+    assertNotEquals(dn.getDatanodeUuid(), nullString);
+  }
+}