HDFS-14081. hdfs dfsadmin -metasave metasave_test results NPE. Contributed by Shweta Yakkali.

Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java

@@ -839,8 +839,13 @@ public class BlockManager implements BlockStatsMXBean {
       new ArrayList<DatanodeStorageInfo>();
     
     NumberReplicas numReplicas = new NumberReplicas();
+    BlockInfo blockInfo = getStoredBlock(block);
+    if (blockInfo == null) {
+      out.println("Block "+ block + " is Null");
+      return;
+    }
     // source node returned is not used
-    chooseSourceDatanodes(getStoredBlock(block), containingNodes,
+    chooseSourceDatanodes(blockInfo, containingNodes,
         containingLiveReplicasNodes, numReplicas,
         new ArrayList<Byte>(), LowRedundancyBlocks.LEVEL);
     
@@ -1765,8 +1770,8 @@ public class BlockManager implements BlockStatsMXBean {
     this.shouldPostponeBlocksFromFuture  = postpone;
   }
 
-
+  @VisibleForTesting
-  private void postponeBlock(Block blk) {
+  void postponeBlock(Block blk) {
     postponedMisreplicatedBlocks.add(blk);
   }
   

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -1768,10 +1768,10 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
   void metaSave(String filename) throws IOException {
     String operationName = "metaSave";
     checkSuperuserPrivilege(operationName);
-    checkOperation(OperationCategory.UNCHECKED);
+    checkOperation(OperationCategory.READ);
     writeLock();
     try {
-      checkOperation(OperationCategory.UNCHECKED);
+      checkOperation(OperationCategory.READ);
       File file = new File(System.getProperty("hadoop.log.dir"), filename);
       PrintWriter out = new PrintWriter(new BufferedWriter(
           new OutputStreamWriter(new FileOutputStream(file), Charsets.UTF_8)));

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java

@@ -94,6 +94,7 @@ import org.apache.hadoop.ipc.RefreshResponse;
 import org.apache.hadoop.ipc.RemoteException;
 import org.apache.hadoop.ipc.protocolPB.GenericRefreshProtocolClientSideTranslatorPB;
 import org.apache.hadoop.ipc.protocolPB.GenericRefreshProtocolPB;
+import org.apache.hadoop.ipc.StandbyException;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.RefreshUserMappingsProtocol;
 import org.apache.hadoop.security.SecurityUtil;
@@ -1537,11 +1538,20 @@ public class DFSAdmin extends FsShell {
           nsId, ClientProtocol.class);
       List<IOException> exceptions = new ArrayList<>();
       for (ProxyAndInfo<ClientProtocol> proxy : proxies) {
-        try{
+        try {
           proxy.getProxy().metaSave(pathname);
           System.out.println("Created metasave file " + pathname
               + " in the log directory of namenode " + proxy.getAddress());
-        } catch (IOException ioe){
+        } catch (RemoteException re) {
+          Exception unwrapped =  re.unwrapRemoteException(
+              StandbyException.class);
+          if (unwrapped instanceof StandbyException) {
+            System.out.println("Skip Standby NameNode, since it cannot perform"
+                + " metasave operation");
+          } else {
+            throw re;
+          }
+        } catch (IOException ioe) {
           System.out.println("Created metasave file " + pathname
               + " in the log directory of namenode " + proxy.getAddress()
               + " failed");

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManager.java

@@ -1478,6 +1478,41 @@ public class TestBlockManager {
     }
   }
 
+  /**
+   * Unit test to check the race condition for adding a Block to
+   * postponedMisreplicatedBlocks set which may not present in BlockManager
+   * thus avoiding NullPointerException.
+   **/
+  @Test
+  public void testMetaSavePostponedMisreplicatedBlocks() throws IOException {
+    bm.postponeBlock(new Block());
+
+    File file = new File("test.log");
+    PrintWriter out = new PrintWriter(file);
+
+    bm.metaSave(out);
+    out.flush();
+
+    FileInputStream fstream = new FileInputStream(file);
+    DataInputStream in = new DataInputStream(fstream);
+
+    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
+    StringBuffer buffer = new StringBuffer();
+    String line;
+    try {
+      while ((line = reader.readLine()) != null) {
+        buffer.append(line);
+      }
+      String output = buffer.toString();
+      assertTrue("Metasave output should not have null block ",
+          output.contains("Block blk_0_0 is Null"));
+
+    } finally {
+      reader.close();
+      file.delete();
+    }
+  }
+
   @Test
   public void testMetaSaveMissingReplicas() throws Exception {
     List<DatanodeStorageInfo> origStorages = getStorages(0, 1);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/tools/TestDFSAdminWithHA.java

@@ -414,16 +414,21 @@ public class TestDFSAdminWithHA {
   @Test (timeout = 30000)
   public void testMetaSave() throws Exception {
     setUpHaCluster(false);
+    cluster.getDfsCluster().transitionToActive(0);
     int exitCode = admin.run(new String[] {"-metasave", "dfs.meta"});
     assertEquals(err.toString().trim(), 0, exitCode);
-    String message = "Created metasave file dfs.meta in the log directory"
+    String messageFromActiveNN = "Created metasave file dfs.meta "
-        + " of namenode.*";
+        + "in the log directory of namenode.*";
-    assertOutputMatches(message + newLine + message + newLine);
+    String messageFromStandbyNN = "Skip Standby NameNode, since it "
+        + "cannot perform metasave operation";
+    assertOutputMatches(messageFromActiveNN + newLine +
+        messageFromStandbyNN + newLine);
   }
 
   @Test (timeout = 30000)
   public void testMetaSaveNN1UpNN2Down() throws Exception {
     setUpHaCluster(false);
+    cluster.getDfsCluster().transitionToActive(0);
     cluster.getDfsCluster().shutdownNameNode(1);
     int exitCode = admin.run(new String[] {"-metasave", "dfs.meta"});
     assertNotEquals(err.toString().trim(), 0, exitCode);
@@ -437,6 +442,7 @@ public class TestDFSAdminWithHA {
   @Test (timeout = 30000)
   public void testMetaSaveNN1DownNN2Up() throws Exception {
     setUpHaCluster(false);
+    cluster.getDfsCluster().transitionToActive(1);
     cluster.getDfsCluster().shutdownNameNode(0);
     int exitCode = admin.run(new String[] {"-metasave", "dfs.meta"});
     assertNotEquals(err.toString().trim(), 0, exitCode);