HDFS-7533. Datanode sometimes does not shutdown on receiving upgrade shutdown command. Contributed by Eric Payne.

(cherry picked from commit 6bbf9fdd04)

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

@@ -416,6 +416,9 @@ Release 2.7.0 - UNRELEASED
     HDFS-7596. NameNode should prune dead storages from storageMap.
     (Arpit Agarwal via cnauroth)
 
+    HDFS-7533. Datanode sometimes does not shutdown on receiving upgrade
+    shutdown command (Eric Payne via kihwal)
+
 Release 2.6.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -1625,9 +1625,13 @@ public class DataNode extends ReconfigurableBase
     // in order to avoid any further acceptance of requests, but the peers
     // for block writes are not closed until the clients are notified.
     if (dataXceiverServer != null) {
-      xserver.sendOOBToPeers();
-      ((DataXceiverServer) this.dataXceiverServer.getRunnable()).kill();
-      this.dataXceiverServer.interrupt();
+      try {
+        xserver.sendOOBToPeers();
+        ((DataXceiverServer) this.dataXceiverServer.getRunnable()).kill();
+        this.dataXceiverServer.interrupt();
+      } catch (Throwable e) {
+        // Ignore, since the out of band messaging is advisory.
+      }
     }
 
     // Interrupt the checkDiskErrorThread and terminate it.

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

@@ -21,6 +21,7 @@ package org.apache.hadoop.hdfs.server.datanode;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 import java.io.IOException;
 
@@ -32,6 +33,7 @@ import org.apache.hadoop.hdfs.MiniDFSNNTopology;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
+import org.mockito.Mockito;
 
 /** 
  * Tests if DataNode process exits if all Block Pool services exit. 
@@ -88,4 +90,18 @@ public class TestDataNodeExit {
     stopBPServiceThreads(2, dn);
     assertFalse("DataNode should exit", dn.isDatanodeUp());
   }
+
+  @Test
+  public void testSendOOBToPeers() throws Exception {
+    DataNode dn = cluster.getDataNodes().get(0);
+    DataXceiverServer spyXserver = Mockito.spy(dn.getXferServer());
+    NullPointerException e = new NullPointerException();
+    Mockito.doThrow(e).when(spyXserver).sendOOBToPeers();
+    dn.xserver = spyXserver;
+    try {
+      dn.shutdown();
+    } catch (Throwable t) {
+      fail("DataNode shutdown should not have thrown exception " + t);
+    }
+  }
 }