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Posted to hdfs-commits@hadoop.apache.org by su...@apache.org on 2013/07/26 06:47:25 UTC

svn commit: r1507191 - in /hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs: ./ src/main/java/org/apache/hadoop/hdfs/ src/main/java/org/apache/hadoop/hdfs/server/datanode/ src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/im...

Author: suresh
Date: Fri Jul 26 04:47:25 2013
New Revision: 1507191

URL: http://svn.apache.org/r1507191
Log:
HDFS-5016. Merge 1507189 from trunk

Modified:
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInPipeline.java
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
    hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestInterDatanodeProtocol.java

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt Fri Jul 26 04:47:25 2013
@@ -516,6 +516,9 @@ Release 2.1.0-beta - 2013-07-02
 
     HDFS-4602. TestBookKeeperHACheckpoints fails. (umamahesh)
 
+    HDFS-5016. Deadlock in pipeline recovery causes Datanode to be marked dead.
+    (suresh)
+
   BREAKDOWN OF HDFS-347 SUBTASKS AND RELATED JIRAS
 
     HDFS-4353. Encapsulate connections to peers in Peer and PeerServer classes.

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java Fri Jul 26 04:47:25 2013
@@ -495,4 +495,9 @@ public class DFSConfigKeys extends Commo
   public static final long DFS_NAMENODE_RETRY_CACHE_EXPIRYTIME_MILLIS_DEFAULT = 600000; // 10 minutes
   public static final String DFS_NAMENODE_RETRY_CACHE_HEAP_PERCENT_KEY = "dfs.namenode.retrycache.heap.percent";
   public static final float DFS_NAMENODE_RETRY_CACHE_HEAP_PERCENT_DEFAULT = 0.03f;
+
+  // Hidden configuration undocumented in hdfs-site. xml
+  // Timeout to wait for block receiver and responder thread to stop
+  public static final String DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_KEY = "dfs.datanode.xceiver.stop.timeout.millis";
+  public static final long   DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT = 60000;
 }

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java Fri Jul 26 04:47:25 2013
@@ -51,6 +51,7 @@ import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.nativeio.NativeIO;
 import org.apache.hadoop.util.Daemon;
 import org.apache.hadoop.util.DataChecksum;
+import org.apache.hadoop.util.StringUtils;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -731,7 +732,13 @@ class BlockReceiver implements Closeable
       }
       if (responder != null) {
         try {
-          responder.join();
+          responder.join(datanode.getDnConf().getXceiverStopTimeout());
+          if (responder.isAlive()) {
+            String msg = "Join on responder thread " + responder
+                + " timed out";
+            LOG.warn(msg + "\n" + StringUtils.getStackTrace(responder));
+            throw new IOException(msg);
+          }
         } catch (InterruptedException e) {
           responder.interrupt();
           throw new IOException("Interrupted receiveBlock");

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java Fri Jul 26 04:47:25 2013
@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.hdfs.server.datanode;
 
+import org.apache.hadoop.classification.InterfaceAudience;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCKREPORT_INITIAL_DELAY_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCKREPORT_INITIAL_DELAY_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCKREPORT_INTERVAL_MSEC_DEFAULT;
@@ -29,6 +30,8 @@ import static org.apache.hadoop.hdfs.DFS
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_SYNCONCLOSE_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_TRANSFERTO_ALLOWED_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_TRANSFERTO_ALLOWED_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_MIN_SUPPORTED_NAMENODE_VERSION_KEY;
@@ -44,7 +47,8 @@ import org.apache.hadoop.hdfs.server.com
  * Simple class encapsulating all of the configuration that the DataNode
  * loads at startup time.
  */
-class DNConf {
+@InterfaceAudience.Private
+public class DNConf {
   final int socketTimeout;
   final int socketWriteTimeout;
   final int socketKeepaliveTimeout;
@@ -66,6 +70,8 @@ class DNConf {
   
   final String minimumNameNodeVersion;
   final String encryptionAlgorithm;
+  
+  final long xceiverStopTimeout;
 
   public DNConf(Configuration conf) {
     socketTimeout = conf.getInt(DFS_CLIENT_SOCKET_TIMEOUT_KEY,
@@ -127,10 +133,18 @@ class DNConf {
     this.encryptDataTransfer = conf.getBoolean(DFS_ENCRYPT_DATA_TRANSFER_KEY,
         DFS_ENCRYPT_DATA_TRANSFER_DEFAULT);
     this.encryptionAlgorithm = conf.get(DFS_DATA_ENCRYPTION_ALGORITHM_KEY);
+    
+    this.xceiverStopTimeout = conf.getLong(
+        DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_KEY,
+        DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
   }
   
   // We get minimumNameNodeVersion via a method so it can be mocked out in tests.
   String getMinimumNameNodeVersion() {
     return this.minimumNameNodeVersion;
   }
+  
+  public long getXceiverStopTimeout() {
+    return xceiverStopTimeout;
+  }
 }

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java Fri Jul 26 04:47:25 2013
@@ -2448,7 +2448,7 @@ public class DataNode extends Configured
     return dxcs.balanceThrottler.getBandwidth();
   }
   
-  DNConf getDnConf() {
+  public DNConf getDnConf() {
     return dnConf;
   }
 

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInPipeline.java
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInPipeline.java?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInPipeline.java (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInPipeline.java Fri Jul 26 04:47:25 2013
@@ -28,6 +28,7 @@ import org.apache.hadoop.hdfs.server.dat
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.util.DataChecksum;
+import org.apache.hadoop.util.StringUtils;
 
 /** 
  * This class defines a replica in a pipeline, which
@@ -150,11 +151,16 @@ public class ReplicaInPipeline extends R
    * Interrupt the writing thread and wait until it dies
    * @throws IOException the waiting is interrupted
    */
-  public void stopWriter() throws IOException {
+  public void stopWriter(long xceiverStopTimeout) throws IOException {
     if (writer != null && writer != Thread.currentThread() && writer.isAlive()) {
       writer.interrupt();
       try {
-        writer.join();
+        writer.join(xceiverStopTimeout);
+        if (writer.isAlive()) {
+          final String msg = "Join on writer thread " + writer + " timed out";
+          DataNode.LOG.warn(msg + "\n" + StringUtils.getStackTrace(writer));
+          throw new IOException(msg);
+        }
       } catch (InterruptedException e) {
         throw new IOException("Waiting for writer thread is interrupted.");
       }

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java Fri Jul 26 04:47:25 2013
@@ -76,7 +76,6 @@ import org.apache.hadoop.hdfs.server.dat
 import org.apache.hadoop.hdfs.server.datanode.metrics.FSDatasetMBean;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
 import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
-import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.nativeio.NativeIO;
 import org.apache.hadoop.metrics2.util.MBeans;
 import org.apache.hadoop.util.DataChecksum;
@@ -615,7 +614,7 @@ class FsDatasetImpl implements FsDataset
     if (replicaInfo.getState() == ReplicaState.RBW) {
       ReplicaBeingWritten rbw = (ReplicaBeingWritten)replicaInfo;
       // kill the previous writer
-      rbw.stopWriter();
+      rbw.stopWriter(datanode.getDnConf().getXceiverStopTimeout());
       rbw.setWriter(Thread.currentThread());
       // check length: bytesRcvd, bytesOnDisk, and bytesAcked should be the same
       if (replicaLen != rbw.getBytesOnDisk() 
@@ -735,7 +734,7 @@ class FsDatasetImpl implements FsDataset
     LOG.info("Recovering " + rbw);
 
     // Stop the previous writer
-    rbw.stopWriter();
+    rbw.stopWriter(datanode.getDnConf().getXceiverStopTimeout());
     rbw.setWriter(Thread.currentThread());
 
     // check generation stamp
@@ -1451,13 +1450,14 @@ class FsDatasetImpl implements FsDataset
   @Override // FsDatasetSpi
   public synchronized ReplicaRecoveryInfo initReplicaRecovery(
       RecoveringBlock rBlock) throws IOException {
-    return initReplicaRecovery(rBlock.getBlock().getBlockPoolId(),
-        volumeMap, rBlock.getBlock().getLocalBlock(), rBlock.getNewGenerationStamp());
+    return initReplicaRecovery(rBlock.getBlock().getBlockPoolId(), volumeMap,
+        rBlock.getBlock().getLocalBlock(), rBlock.getNewGenerationStamp(),
+        datanode.getDnConf().getXceiverStopTimeout());
   }
 
   /** static version of {@link #initReplicaRecovery(Block, long)}. */
-  static ReplicaRecoveryInfo initReplicaRecovery(String bpid,
-      ReplicaMap map, Block block, long recoveryId) throws IOException {
+  static ReplicaRecoveryInfo initReplicaRecovery(String bpid, ReplicaMap map,
+      Block block, long recoveryId, long xceiverStopTimeout) throws IOException {
     final ReplicaInfo replica = map.get(bpid, block.getBlockId());
     LOG.info("initReplicaRecovery: " + block + ", recoveryId=" + recoveryId
         + ", replica=" + replica);
@@ -1470,7 +1470,7 @@ class FsDatasetImpl implements FsDataset
     //stop writer if there is any
     if (replica instanceof ReplicaInPipeline) {
       final ReplicaInPipeline rip = (ReplicaInPipeline)replica;
-      rip.stopWriter();
+      rip.stopWriter(xceiverStopTimeout);
 
       //check replica bytes on disk.
       if (rip.getBytesOnDisk() < rip.getVisibleLength()) {

Modified: hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestInterDatanodeProtocol.java
URL: http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestInterDatanodeProtocol.java?rev=1507191&r1=1507190&r2=1507191&view=diff
==============================================================================
--- hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestInterDatanodeProtocol.java (original)
+++ hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestInterDatanodeProtocol.java Fri Jul 26 04:47:25 2013
@@ -167,7 +167,7 @@ public class TestInterDatanodeProtocol {
       cluster.waitActive();
 
       //create a file
-      DistributedFileSystem dfs = (DistributedFileSystem)cluster.getFileSystem();
+      DistributedFileSystem dfs = cluster.getFileSystem();
       String filestr = "/foo";
       Path filepath = new Path(filestr);
       DFSTestUtil.createFile(dfs, filepath, 1024L, (short)3, 0L);
@@ -225,7 +225,7 @@ public class TestInterDatanodeProtocol {
   }
 
   /** Test 
-   * {@link FsDatasetImpl#initReplicaRecovery(String, ReplicaMap, Block, long)}
+   * {@link FsDatasetImpl#initReplicaRecovery(String, ReplicaMap, Block, long, long)}
    */
   @Test
   public void testInitReplicaRecovery() throws IOException {
@@ -246,8 +246,9 @@ public class TestInterDatanodeProtocol {
       final ReplicaInfo originalInfo = map.get(bpid, b);
 
       final long recoveryid = gs + 1;
-      final ReplicaRecoveryInfo recoveryInfo = FsDatasetImpl.initReplicaRecovery(
-          bpid, map, blocks[0], recoveryid);
+      final ReplicaRecoveryInfo recoveryInfo = FsDatasetImpl
+          .initReplicaRecovery(bpid, map, blocks[0], recoveryid,
+              DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
       assertEquals(originalInfo, recoveryInfo);
 
       final ReplicaUnderRecovery updatedInfo = (ReplicaUnderRecovery)map.get(bpid, b);
@@ -256,7 +257,9 @@ public class TestInterDatanodeProtocol {
 
       //recover one more time 
       final long recoveryid2 = gs + 2;
-      final ReplicaRecoveryInfo recoveryInfo2 = FsDatasetImpl.initReplicaRecovery(bpid, map, blocks[0], recoveryid2);
+      final ReplicaRecoveryInfo recoveryInfo2 = FsDatasetImpl
+          .initReplicaRecovery(bpid, map, blocks[0], recoveryid2,
+              DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
       assertEquals(originalInfo, recoveryInfo2);
 
       final ReplicaUnderRecovery updatedInfo2 = (ReplicaUnderRecovery)map.get(bpid, b);
@@ -265,7 +268,8 @@ public class TestInterDatanodeProtocol {
       
       //case RecoveryInProgressException
       try {
-        FsDatasetImpl.initReplicaRecovery(bpid, map, b, recoveryid);
+        FsDatasetImpl.initReplicaRecovery(bpid, map, b, recoveryid,
+            DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
         Assert.fail();
       }
       catch(RecoveryInProgressException ripe) {
@@ -276,7 +280,9 @@ public class TestInterDatanodeProtocol {
     { // BlockRecoveryFI_01: replica not found
       final long recoveryid = gs + 1;
       final Block b = new Block(firstblockid - 1, length, gs);
-      ReplicaRecoveryInfo r = FsDatasetImpl.initReplicaRecovery(bpid, map, b, recoveryid);
+      ReplicaRecoveryInfo r = FsDatasetImpl.initReplicaRecovery(bpid, map, b,
+          recoveryid,
+          DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
       Assert.assertNull("Data-node should not have this replica.", r);
     }
     
@@ -284,7 +290,8 @@ public class TestInterDatanodeProtocol {
       final long recoveryid = gs - 1;
       final Block b = new Block(firstblockid + 1, length, gs);
       try {
-        FsDatasetImpl.initReplicaRecovery(bpid, map, b, recoveryid);
+        FsDatasetImpl.initReplicaRecovery(bpid, map, b, recoveryid,
+            DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
         Assert.fail();
       }
       catch(IOException ioe) {
@@ -297,7 +304,8 @@ public class TestInterDatanodeProtocol {
       final long recoveryid = gs + 1;
       final Block b = new Block(firstblockid, length, gs+1);
       try {
-        FsDatasetImpl.initReplicaRecovery(bpid, map, b, recoveryid);
+        FsDatasetImpl.initReplicaRecovery(bpid, map, b, recoveryid,
+            DFSConfigKeys.DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
         fail("InitReplicaRecovery should fail because replica's " +
         		"gs is less than the block's gs");
       } catch (IOException e) {
@@ -321,7 +329,7 @@ public class TestInterDatanodeProtocol {
       String bpid = cluster.getNamesystem().getBlockPoolId();
 
       //create a file
-      DistributedFileSystem dfs = (DistributedFileSystem)cluster.getFileSystem();
+      DistributedFileSystem dfs = cluster.getFileSystem();
       String filestr = "/foo";
       Path filepath = new Path(filestr);
       DFSTestUtil.createFile(dfs, filepath, 1024L, (short)3, 0L);