HDFS-9949. Add a test case to ensure that the DataNode does not regenerate its UUID when a storage directory is cleared (Harsh J via cmccabe)

(cherry picked from commit dc951e606f)
(cherry picked from commit f69a6c3632)

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

@@ -19,17 +19,21 @@
 package org.apache.hadoop.hdfs.server.datanode;
 
 
+import org.apache.commons.io.FileUtils;
 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.apache.hadoop.hdfs.MiniDFSCluster;
 import org.junit.Test;
 
+import java.io.File;
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
 
 public class TestDataNodeUUID {
 
@@ -62,4 +66,52 @@ public class TestDataNodeUUID {
     // Make sure that we have a valid DataNodeUUID at that point of time.
     assertNotEquals(dn.getDatanodeUuid(), nullString);
   }
+
+  @Test(timeout = 10000)
+  public void testUUIDRegeneration() throws Exception {
+    File baseDir = new File(System.getProperty("test.build.data"));
+    File disk1 = new File(baseDir, "disk1");
+    File disk2 = new File(baseDir, "disk2");
+
+    // Ensure the configured disks do not pre-exist
+    FileUtils.deleteDirectory(disk1);
+    FileUtils.deleteDirectory(disk2);
+
+    MiniDFSCluster cluster = null;
+    HdfsConfiguration conf = new HdfsConfiguration();
+    conf.setStrings(DFSConfigKeys.DFS_DATANODE_DATA_DIR_KEY,
+            disk1.toURI().toString(),
+            disk2.toURI().toString());
+    try {
+      cluster = new MiniDFSCluster.Builder(conf)
+              .numDataNodes(1)
+              .manageDataDfsDirs(false)
+              .build();
+      cluster.waitActive();
+
+      // Grab the new-cluster UUID as the original one to test against
+      String originalUUID = cluster.getDataNodes().get(0).getDatanodeUuid();
+      // Stop and simulate a DN wipe or unmount-but-root-path condition
+      // on the second disk
+      MiniDFSCluster.DataNodeProperties dn = cluster.stopDataNode(0);
+      FileUtils.deleteDirectory(disk2);
+      assertTrue("Failed to recreate the data directory: " + disk2,
+              disk2.mkdirs());
+
+      // Restart and check if the UUID changed
+      assertTrue("DataNode failed to start up: " + dn,
+              cluster.restartDataNode(dn));
+      // We need to wait until the DN has completed registration
+      while (!cluster.getDataNodes().get(0).isDatanodeFullyStarted()) {
+        Thread.sleep(50);
+      }
+      assertEquals(
+              "DN generated a new UUID despite disk1 having it intact",
+              originalUUID, cluster.getDataNodes().get(0).getDatanodeUuid());
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+    }
+  }
 }