HDFS-15806. DeadNodeDetector should close all the threads when it is closed. Contributed by Jinglun.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/ClientContext.java

@@ -321,13 +321,7 @@ synchronized void unreference() {
     Preconditions.checkState(counter > 0);
     counter--;
     if (counter == 0 && deadNodeDetectionEnabled && deadNodeDetector != null) {
-      deadNodeDetector.interrupt();
+      deadNodeDetector.shutdown();
-      try {
-        deadNodeDetector.join();
-      } catch (InterruptedException e) {
-        LOG.warn("Encountered exception while waiting to join on dead " +
-            "node detector thread.", e);
-      }
       deadNodeDetector = null;
     }
   }

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DeadNodeDetector.java

@@ -271,6 +271,37 @@ public void run() {
     }
   }
 
+  /**
+   * Shutdown all the threads.
+   */
+  public void shutdown() {
+    threadShutDown(this);
+    threadShutDown(probeDeadNodesSchedulerThr);
+    threadShutDown(probeSuspectNodesSchedulerThr);
+    probeDeadNodesThreadPool.shutdown();
+    probeSuspectNodesThreadPool.shutdown();
+    rpcThreadPool.shutdown();
+  }
+
+  private static void threadShutDown(Thread thread) {
+    if (thread != null && thread.isAlive()) {
+      thread.interrupt();
+      try {
+        thread.join();
+      } catch (InterruptedException e) {
+      }
+    }
+  }
+
+  @VisibleForTesting
+  boolean isThreadsShutdown() {
+    return !this.isAlive() && !probeDeadNodesSchedulerThr.isAlive()
+        && !probeSuspectNodesSchedulerThr.isAlive()
+        && probeDeadNodesThreadPool.isShutdown()
+        && probeSuspectNodesThreadPool.isShutdown()
+        && rpcThreadPool.isShutdown();
+  }
+
   @VisibleForTesting
   static void setDisabledProbeThreadForTest(
       boolean disabledProbeThreadForTest) {

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

@@ -357,6 +357,18 @@ public void testCloseDeadNodeDetector() throws Exception {
     dfs1.close();
   }
 
+  @Test
+  public void testDeadNodeDetectorThreadsShutdown() throws Exception {
+    DistributedFileSystem dfs = (DistributedFileSystem) FileSystem
+        .newInstance(new URI("hdfs://127.0.0.1:2001/"), conf);
+    DeadNodeDetector detector = dfs.getClient().getDeadNodeDetector();
+    assertNotNull(detector);
+    dfs.close();
+    assertTrue(detector.isThreadsShutdown());
+    detector = dfs.getClient().getDeadNodeDetector();
+    assertNull(detector);
+  }
+
   private void createFile(FileSystem fs, Path filePath) throws IOException {
     FSDataOutputStream out = null;
     try {