HDFS-2979. Balancer should use logical uri for creating failover proxy with HA enabled. Contributed by Aaron T. Myers.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-1623@1295340 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt

@@ -242,3 +242,5 @@ HDFS-2958. Sweep for remaining proxy construction which doesn't go through failo
 HDFS-2920. fix remaining TODO items. (atm and todd)
 
 HDFS-3027. Implement a simple NN health check. (atm)
+
+HDFS-2979. Balancer should use logical uri for creating failover proxy with HA enabled. (atm)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java

@@ -28,9 +28,11 @@ import java.security.SecureRandom;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
+import java.util.Set;
 import java.util.StringTokenizer;
 
 import javax.net.SocketFactory;
@@ -43,6 +45,7 @@ import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.protocol.ClientDatanodeProtocol;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
+import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocolPB.ClientDatanodeProtocolTranslatorPB;
@@ -605,6 +608,68 @@ public class DFSUtil {
         "nnId=" + namenodeId + ";addr=" + addr + "]";
     }
   }
+  
+  /**
+   * Get a URI for each configured nameservice. If a nameservice is
+   * HA-enabled, then the logical URI of the nameservice is returned. If the
+   * nameservice is not HA-enabled, then a URI corresponding to an RPC address
+   * of the single NN for that nameservice is returned, preferring the service
+   * RPC address over the client RPC address.
+   * 
+   * @param conf configuration
+   * @return a collection of all configured NN URIs, preferring service
+   *         addresses
+   */
+  public static Collection<URI> getNsServiceRpcUris(Configuration conf) {
+    return getNameServiceUris(conf,
+        DFSConfigKeys.DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY,
+        DFSConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY);
+  }
+
+  /**
+   * Get a URI for each configured nameservice. If a nameservice is
+   * HA-enabled, then the logical URI of the nameservice is returned. If the
+   * nameservice is not HA-enabled, then a URI corresponding to the address of
+   * the single NN for that nameservice is returned.
+   * 
+   * @param conf configuration
+   * @param keys configuration keys to try in order to get the URI for non-HA
+   *        nameservices
+   * @return a collection of all configured NN URIs
+   */
+  public static Collection<URI> getNameServiceUris(Configuration conf,
+      String... keys) {
+    Set<URI> ret = new HashSet<URI>();
+    for (String nsId : getNameServiceIds(conf)) {
+      if (HAUtil.isHAEnabled(conf, nsId)) {
+        // Add the logical URI of the nameservice.
+        try {
+          ret.add(new URI(HdfsConstants.HDFS_URI_SCHEME + "://" + nsId));
+        } catch (URISyntaxException ue) {
+          throw new IllegalArgumentException(ue);
+        }
+      } else {
+        // Add the URI corresponding to the address of the NN.
+        for (String key : keys) {
+          String addr = conf.get(concatSuffixes(key, nsId));
+          if (addr != null) {
+            ret.add(createUri(HdfsConstants.HDFS_URI_SCHEME,
+                NetUtils.createSocketAddr(addr)));
+            break;
+          }
+        }
+      }
+    }
+    // Add the generic configuration keys.
+    for (String key : keys) {
+      String addr = conf.get(key);
+      if (addr != null) {
+        ret.add(createUri("hdfs", NetUtils.createSocketAddr(addr)));
+        break;
+      }
+    }
+    return ret;
+  }
 
   /**
    * Given the InetSocketAddress this method returns the nameservice Id

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/Balancer.java

@@ -24,8 +24,8 @@ import java.io.BufferedOutputStream;
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
-import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.net.URI;
 import java.text.DateFormat;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -39,7 +39,6 @@ import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -1380,8 +1379,7 @@ public class Balancer {
    * for each namenode,
    * execute a {@link Balancer} to work through all datanodes once.  
    */
-  static int run(Map<String, Map<String, InetSocketAddress>> namenodes,
-      final Parameters p,
+  static int run(Collection<URI> namenodes, final Parameters p,
       Configuration conf) throws IOException, InterruptedException {
     final long sleeptime = 2000*conf.getLong(
         DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY,
@@ -1395,10 +1393,8 @@ public class Balancer {
     final List<NameNodeConnector> connectors
         = new ArrayList<NameNodeConnector>(namenodes.size());
     try {
-      for(Entry<String, Map<String, InetSocketAddress>> entry :
-          namenodes.entrySet()) {
-        connectors.add(
-            new NameNodeConnector(entry.getValue().values(), conf));
+      for (URI uri : namenodes) {
+        connectors.add(new NameNodeConnector(uri, conf));
       }
     
       boolean done = false;
@@ -1480,8 +1476,7 @@ public class Balancer {
       try {
         checkReplicationPolicyCompatibility(conf);
 
-        final Map<String, Map<String, InetSocketAddress>> namenodes =
-          DFSUtil.getNNServiceRpcAddresses(conf);
+        final Collection<URI> namenodes = DFSUtil.getNsServiceRpcUris(conf);
         return Balancer.run(namenodes, parse(args), conf);
       } catch (IOException e) {
         System.out.println(e + ".  Exiting ...");

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/NameNodeConnector.java

@@ -21,9 +21,7 @@ import java.io.DataOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.net.InetAddress;
-import java.net.InetSocketAddress;
 import java.net.URI;
-import java.util.Collection;
 import java.util.EnumSet;
 
 import org.apache.commons.logging.Log;
@@ -38,7 +36,6 @@ import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager;
 import org.apache.hadoop.hdfs.security.token.block.ExportedBlockKeys;
-import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocol;
 import org.apache.hadoop.hdfs.server.protocol.NamespaceInfo;
 import org.apache.hadoop.io.IOUtils;
@@ -46,8 +43,6 @@ import org.apache.hadoop.ipc.RemoteException;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.Daemon;
 
-import com.google.common.collect.Lists;
-
 /**
  * The class provides utilities for {@link Balancer} to access a NameNode
  */
@@ -56,7 +51,7 @@ class NameNodeConnector {
   private static final Log LOG = Balancer.LOG;
   private static final Path BALANCER_ID_PATH = new Path("/system/balancer.id");
 
-  final InetSocketAddress namenodeAddress;
+  final URI nameNodeUri;
   final String blockpoolID;
 
   final NamenodeProtocol namenode;
@@ -70,10 +65,9 @@ class NameNodeConnector {
   private BlockTokenSecretManager blockTokenSecretManager;
   private Daemon keyupdaterthread; // AccessKeyUpdater thread
 
-  NameNodeConnector(Collection<InetSocketAddress> haNNs,
+  NameNodeConnector(URI nameNodeUri,
       Configuration conf) throws IOException {
-    this.namenodeAddress = Lists.newArrayList(haNNs).get(0);
-    URI nameNodeUri = NameNode.getUri(this.namenodeAddress);
+    this.nameNodeUri = nameNodeUri;
     
     this.namenode =
       NameNodeProxies.createProxy(conf, nameNodeUri, NamenodeProtocol.class)
@@ -186,7 +180,7 @@ class NameNodeConnector {
 
   @Override
   public String toString() {
-    return getClass().getSimpleName() + "[namenodeAddress=" + namenodeAddress
+    return getClass().getSimpleName() + "[namenodeUri=" + nameNodeUri
         + ", id=" + blockpoolID
         + "]";
   }

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

@@ -526,21 +526,21 @@ public class NameNode {
 
   protected NameNode(Configuration conf, NamenodeRole role) 
       throws IOException { 
-    this.conf = conf;
+    this.conf = new Configuration(conf);
     this.role = role;
-    String nsId = getNameServiceId(conf);
-    String namenodeId = HAUtil.getNameNodeId(conf, nsId);
-    this.haEnabled = HAUtil.isHAEnabled(conf, nsId);
+    String nsId = getNameServiceId(this.conf);
+    String namenodeId = HAUtil.getNameNodeId(this.conf, nsId);
+    this.haEnabled = HAUtil.isHAEnabled(this.conf, nsId);
     if (!haEnabled) {
       state = ACTIVE_STATE;
     } else {
       state = STANDBY_STATE;
     }
-    this.allowStaleStandbyReads = HAUtil.shouldAllowStandbyReads(conf);
+    this.allowStaleStandbyReads = HAUtil.shouldAllowStandbyReads(this.conf);
     this.haContext = createHAContext();
     try {
-      initializeGenericKeys(conf, nsId, namenodeId);
-      initialize(conf);
+      initializeGenericKeys(this.conf, nsId, namenodeId);
+      initialize(this.conf);
       state.prepareToEnterState(haContext);
       state.enterState(haContext);
     } catch (IOException e) {
@@ -651,6 +651,7 @@ public class NameNode {
       throws IOException {
     String nsId = DFSUtil.getNamenodeNameServiceId(conf);
     String namenodeId = HAUtil.getNameNodeId(conf, nsId);
+    conf = new Configuration(conf);
     initializeGenericKeys(conf, nsId, namenodeId);
 
     if (!conf.getBoolean(DFS_NAMENODE_SUPPORT_ALLOW_FORMAT_KEY, 
@@ -697,6 +698,7 @@ public class NameNode {
   private static boolean finalize(Configuration conf,
                                boolean isConfirmationNeeded
                                ) throws IOException {
+    conf = new Configuration(conf);
     String nsId = DFSUtil.getNamenodeNameServiceId(conf);
     String namenodeId = HAUtil.getNameNodeId(conf, nsId);
     initializeGenericKeys(conf, nsId, namenodeId);

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

@@ -25,6 +25,8 @@ import static org.junit.Assert.*;
 
 import java.io.IOException;
 import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URISyntaxException;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
@@ -41,6 +43,8 @@ import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.BlockLocation;
+import org.apache.hadoop.fs.CommonConfigurationKeys;
+
 import static org.apache.hadoop.hdfs.DFSConfigKeys.*;
 
 public class TestDFSUtil {
@@ -233,11 +237,12 @@ public class TestDFSUtil {
    * {@link DFSUtil#isDefaultNamenodeAddress(Configuration, InetSocketAddress, String...)}
    */
   @Test
-  public void testSingleNamenode() {
+  public void testSingleNamenode() throws URISyntaxException {
     HdfsConfiguration conf = new HdfsConfiguration();
     final String DEFAULT_ADDRESS = "localhost:9000";
     final String NN2_ADDRESS = "localhost:9001";
     conf.set(DFS_NAMENODE_RPC_ADDRESS_KEY, DEFAULT_ADDRESS);
+    conf.set(CommonConfigurationKeys.FS_DEFAULT_NAME_KEY, DEFAULT_ADDRESS);
 
     InetSocketAddress testAddress1 = NetUtils.createSocketAddr(DEFAULT_ADDRESS);
     boolean isDefault = DFSUtil.isDefaultNamenodeAddress(conf, testAddress1,
@@ -247,6 +252,10 @@ public class TestDFSUtil {
     isDefault = DFSUtil.isDefaultNamenodeAddress(conf, testAddress2,
         DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY, DFS_NAMENODE_RPC_ADDRESS_KEY);
     assertFalse(isDefault);
+    
+    Collection<URI> uris = DFSUtil.getNameServiceUris(conf, DFS_NAMENODE_RPC_ADDRESS_KEY);
+    assertEquals(1, uris.size());
+    assertTrue(uris.contains(new URI("hdfs://" + DEFAULT_ADDRESS)));
   }
 
   /** Tests to ensure default namenode is used as fallback */
@@ -407,13 +416,14 @@ public class TestDFSUtil {
   }
   
   @Test
-  public void testHANameNodesWithFederation() {
+  public void testHANameNodesWithFederation() throws URISyntaxException {
     HdfsConfiguration conf = new HdfsConfiguration();
     
     final String NS1_NN1_HOST = "ns1-nn1.example.com:8020";
     final String NS1_NN2_HOST = "ns1-nn2.example.com:8020";
     final String NS2_NN1_HOST = "ns2-nn1.example.com:8020";
     final String NS2_NN2_HOST = "ns2-nn2.example.com:8020";
+    conf.set(CommonConfigurationKeys.FS_DEFAULT_NAME_KEY, "hdfs://ns1");
     
     // Two nameservices, each with two NNs.
     conf.set(DFS_FEDERATION_NAMESERVICES, "ns1,ns2");
@@ -460,6 +470,11 @@ public class TestDFSUtil {
     // Ditto for nameservice IDs, if multiple are defined
     assertEquals(null, DFSUtil.getNamenodeNameServiceId(conf));
     assertEquals(null, DFSUtil.getSecondaryNameServiceId(conf));
+    
+    Collection<URI> uris = DFSUtil.getNameServiceUris(conf, DFS_NAMENODE_RPC_ADDRESS_KEY);
+    assertEquals(2, uris.size());
+    assertTrue(uris.contains(new URI("hdfs://ns1")));
+    assertTrue(uris.contains(new URI("hdfs://ns2")));
   }
 
   @Test
@@ -509,4 +524,34 @@ public class TestDFSUtil {
     assertEquals("127.0.0.1:12345",
         DFSUtil.substituteForWildcardAddress("127.0.0.1:12345", "foo"));
   }
+  
+  @Test
+  public void testGetNNUris() throws Exception {
+    HdfsConfiguration conf = new HdfsConfiguration();
+    
+    final String NS1_NN1_HOST = "ns1-nn1.example.com:8020";
+    final String NS1_NN2_HOST = "ns1-nn1.example.com:8020";
+    final String NS2_NN_HOST  = "ns2-nn.example.com:8020";
+    final String NN_HOST      = "nn.example.com:8020";
+    
+    conf.set(DFS_FEDERATION_NAMESERVICES, "ns1,ns2");
+    conf.set(DFSUtil.addKeySuffixes(DFS_HA_NAMENODES_KEY_PREFIX, "ns1"),"nn1,nn2");
+    conf.set(DFSUtil.addKeySuffixes(
+        DFS_NAMENODE_RPC_ADDRESS_KEY, "ns1", "nn1"), NS1_NN1_HOST);
+    conf.set(DFSUtil.addKeySuffixes(
+        DFS_NAMENODE_RPC_ADDRESS_KEY, "ns1", "nn2"), NS1_NN2_HOST);
+    
+    conf.set(DFSUtil.addKeySuffixes(DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY, "ns2"),
+        NS2_NN_HOST);
+    
+    conf.set(DFS_NAMENODE_RPC_ADDRESS_KEY, "hdfs://" + NN_HOST);
+    
+    Collection<URI> uris = DFSUtil.getNameServiceUris(conf, DFS_NAMENODE_RPC_ADDRESS_KEY, 
+        DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY);
+    
+    assertEquals(3, uris.size());
+    assertTrue(uris.contains(new URI("hdfs://ns1")));
+    assertTrue(uris.contains(new URI("hdfs://" + NS2_NN_HOST)));
+    assertTrue(uris.contains(new URI("hdfs://" + NN_HOST)));
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/balancer/TestBalancer.java

@@ -18,11 +18,11 @@
 package org.apache.hadoop.hdfs.server.balancer;
 
 import java.io.IOException;
-import java.net.InetSocketAddress;
+import java.net.URI;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.List;
-import java.util.Map;
 import java.util.Random;
 import java.util.concurrent.TimeoutException;
 
@@ -338,8 +338,7 @@ public class TestBalancer extends TestCase {
     waitForHeartBeat(totalUsedSpace, totalCapacity, client, cluster);
 
     // start rebalancing
-    Map<String, Map<String, InetSocketAddress>> namenodes =
-      DFSUtil.getNNServiceRpcAddresses(conf);
+    Collection<URI> namenodes = DFSUtil.getNsServiceRpcUris(conf);
     final int r = Balancer.run(namenodes, Balancer.Parameters.DEFALUT, conf);
     assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/balancer/TestBalancerWithHANameNodes.java

@@ -18,9 +18,10 @@
 package org.apache.hadoop.hdfs.server.balancer;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
-import java.net.InetSocketAddress;
-import java.util.Map;
+import java.net.URI;
+import java.util.Collection;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileSystem;
@@ -67,12 +68,12 @@ public class TestBalancerWithHANameNodes {
     int numOfDatanodes = capacities.length;
     NNConf nn1Conf = new MiniDFSNNTopology.NNConf("nn1");
     nn1Conf.setIpcPort(NameNode.DEFAULT_PORT);
-    MiniDFSNNTopology simpleHATopology = new MiniDFSNNTopology()
-        .addNameservice(new MiniDFSNNTopology.NSConf(null).addNN(nn1Conf)
-            .addNN(new MiniDFSNNTopology.NNConf("nn2")));
-    cluster = new MiniDFSCluster.Builder(conf).nnTopology(simpleHATopology)
-        .numDataNodes(capacities.length).racks(racks).simulatedCapacities(
-            capacities).build();
+    cluster = new MiniDFSCluster.Builder(conf)
+        .nnTopology(MiniDFSNNTopology.simpleHATopology())
+        .numDataNodes(capacities.length)
+        .racks(racks)
+        .simulatedCapacities(capacities)
+        .build();
     HATestUtil.setFailoverConfigurations(cluster, conf);
     try {
       cluster.waitActive();
@@ -89,14 +90,12 @@ public class TestBalancerWithHANameNodes {
       // start up an empty node with the same capacity and on the same rack
       cluster.startDataNodes(conf, 1, true, null, new String[] { newNodeRack },
           new long[] { newNodeCapacity });
-
-      HATestUtil.setFailoverConfigurations(cluster, conf, NameNode.getUri(
-          cluster.getNameNode(0).getNameNodeAddress()).getHost());
       totalCapacity += newNodeCapacity;
       TestBalancer.waitForHeartBeat(totalUsedSpace, totalCapacity, client,
           cluster);
-      Map<String, Map<String, InetSocketAddress>> namenodes = DFSUtil
-          .getNNServiceRpcAddresses(conf);
+      Collection<URI> namenodes = DFSUtil.getNsServiceRpcUris(conf);
+      assertEquals(1, namenodes.size());
+      assertTrue(namenodes.contains(HATestUtil.getLogicalUri(cluster)));
       final int r = Balancer.run(namenodes, Balancer.Parameters.DEFALUT, conf);
       assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
       TestBalancer.waitForBalancer(totalUsedSpace, totalCapacity, client,

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/balancer/TestBalancerWithMultipleNameNodes.java

@@ -18,10 +18,10 @@
 package org.apache.hadoop.hdfs.server.balancer;
 
 import java.io.IOException;
-import java.net.InetSocketAddress;
+import java.net.URI;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.List;
-import java.util.Map;
 import java.util.Random;
 
 import org.apache.commons.logging.Log;
@@ -40,8 +40,8 @@ import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
-import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
+import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.hdfs.server.namenode.LeaseManager;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
@@ -157,8 +157,7 @@ public class TestBalancerWithMultipleNameNodes {
     LOG.info("BALANCER 1");
 
     // start rebalancing
-    final Map<String, Map<String, InetSocketAddress>> namenodes =
-      DFSUtil.getNNServiceRpcAddresses(s.conf);
+    final Collection<URI> namenodes = DFSUtil.getNsServiceRpcUris(s.conf);
     final int r = Balancer.run(namenodes, Balancer.Parameters.DEFALUT, s.conf);
     Assert.assertEquals(Balancer.ReturnStatus.SUCCESS.code, r);
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/HATestUtil.java

@@ -35,6 +35,7 @@ import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
 import org.apache.hadoop.hdfs.server.datanode.DataNodeAdapter;
 import org.apache.hadoop.hdfs.server.namenode.FSImageTestUtil;
@@ -188,6 +189,12 @@ public abstract class HATestUtil {
     return String.format(LOGICAL_HOSTNAME, cluster.getInstanceId());
   }
   
+  public static URI getLogicalUri(MiniDFSCluster cluster)
+      throws URISyntaxException {
+    return new URI(HdfsConstants.HDFS_URI_SCHEME + "://" +
+        getLogicalHostname(cluster));
+  }
+  
   public static void waitForCheckpoint(MiniDFSCluster cluster, int nnIdx,
       List<Integer> txids) throws InterruptedException {
     long start = System.currentTimeMillis();