HDFS-11247. Add a test to verify NameNodeMXBean#getDecomNodes() and Live/Dead Decom Nodes shown in NameNode WebUI. Contributed by Manoj Govindassamy.

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

@@ -315,6 +315,106 @@ public void testLastContactTime() throws Exception {
     }
   }
 
+  @Test (timeout = 120000)
+  public void testDecommissioningNodes() throws Exception {
+    Configuration conf = new Configuration();
+    conf.setInt(DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY, 1);
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_HEARTBEAT_RECHECK_INTERVAL_KEY, 30);
+    MiniDFSCluster cluster = null;
+    HostsFileWriter hostsFileWriter = new HostsFileWriter();
+    hostsFileWriter.initialize(conf, "temp/TestNameNodeMXBean");
+
+    try {
+      cluster = new MiniDFSCluster.Builder(conf).numDataNodes(3).build();
+      cluster.waitActive();
+
+      FSNamesystem fsn = cluster.getNameNode().namesystem;
+      MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
+      ObjectName mxbeanName = new ObjectName(
+          "Hadoop:service=NameNode,name=NameNodeInfo");
+
+      List<String> hosts = new ArrayList<>();
+      for(DataNode dn : cluster.getDataNodes()) {
+        hosts.add(dn.getDisplayName());
+      }
+      hostsFileWriter.initIncludeHosts(hosts.toArray(
+          new String[hosts.size()]));
+      fsn.getBlockManager().getDatanodeManager().refreshNodes(conf);
+
+      // 1. Verify Live nodes
+      String liveNodesInfo = (String) (mbs.getAttribute(mxbeanName,
+          "LiveNodes"));
+      Map<String, Map<String, Object>> liveNodes =
+          (Map<String, Map<String, Object>>) JSON.parse(liveNodesInfo);
+      assertEquals(fsn.getLiveNodes(), liveNodesInfo);
+      assertEquals(fsn.getNumLiveDataNodes(), liveNodes.size());
+
+      for (Map<String, Object> liveNode : liveNodes.values()) {
+        assertTrue(liveNode.containsKey("lastContact"));
+        assertTrue(liveNode.containsKey("xferaddr"));
+      }
+
+      // Add the 1st DataNode to Decommission list
+      hostsFileWriter.initExcludeHost(
+          cluster.getDataNodes().get(0).getDisplayName());
+      fsn.getBlockManager().getDatanodeManager().refreshNodes(conf);
+
+      // Wait for the DecommissionManager to complete refresh nodes
+      GenericTestUtils.waitFor(new Supplier<Boolean>() {
+        @Override
+        public Boolean get() {
+          try {
+            String decomNodesInfo = (String) (mbs.getAttribute(mxbeanName,
+                "DecomNodes"));
+            Map<String, Map<String, Object>> decomNodes =
+                (Map<String, Map<String, Object>>) JSON.parse(decomNodesInfo);
+            if (decomNodes.size() > 0) {
+              return true;
+            }
+          } catch (Exception e) {
+            return false;
+          }
+          return false;
+        }
+      }, 1000, 60000);
+
+      // 2. Verify Decommission InProgress nodes
+      String decomNodesInfo = (String) (mbs.getAttribute(mxbeanName,
+          "DecomNodes"));
+      Map<String, Map<String, Object>> decomNodes =
+          (Map<String, Map<String, Object>>) JSON.parse(decomNodesInfo);
+      assertEquals(fsn.getDecomNodes(), decomNodesInfo);
+      assertEquals(fsn.getNumDecommissioningDataNodes(), decomNodes.size());
+      assertEquals(0, fsn.getNumDecomLiveDataNodes());
+      assertEquals(0, fsn.getNumDecomDeadDataNodes());
+
+      // Wait for the DecommissionManager to complete check
+      GenericTestUtils.waitFor(new Supplier<Boolean>() {
+        @Override
+        public Boolean get() {
+          if (fsn.getNumDecomLiveDataNodes() == 1) {
+            return true;
+          }
+          return false;
+        }
+      }, 1000, 60000);
+
+      // 3. Verify Decommissioned nodes
+      decomNodesInfo = (String) (mbs.getAttribute(mxbeanName, "DecomNodes"));
+      decomNodes =
+          (Map<String, Map<String, Object>>) JSON.parse(decomNodesInfo);
+      assertEquals(0, decomNodes.size());
+      assertEquals(fsn.getDecomNodes(), decomNodesInfo);
+      assertEquals(1, fsn.getNumDecomLiveDataNodes());
+      assertEquals(0, fsn.getNumDecomDeadDataNodes());
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+      hostsFileWriter.cleanup();
+    }
+  }
+
   @Test(timeout=120000)
   @SuppressWarnings("unchecked")
   public void testTopUsers() throws Exception {