HDFS-4521. Invalid network toploogies should not be cached. Contributed by Colin Patrick McCabe.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1457883 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/CachedDNSToSwitchMapping.java

@@ -149,4 +149,9 @@ public class CachedDNSToSwitchMapping extends AbstractDNSToSwitchMapping {
   public boolean isSingleSwitch() {
     return isMappingSingleSwitch(rawMapping);
   }
+  
+  @Override
+  public void reloadCachedMappings() {
+    cache.clear();
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/DNSToSwitchMapping.java

@@ -51,4 +51,12 @@ public interface DNSToSwitchMapping {
    * If <i>names</i> is empty, the returned list is also empty
    */
   public List<String> resolve(List<String> names);
+
+  /**
+   * Reload all of the cached mappings.
+   *
+   * If there is a cache, this method will clear it, so that future accesses
+   * will get a chance to see the new data.
+   */
+  public void reloadCachedMappings();
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetworkTopology.java

@@ -342,8 +342,16 @@ public class NetworkTopology {
       throw new IllegalArgumentException(
         "Not allow to add an inner node: "+NodeBase.getPath(node));
     }
+    int newDepth = NodeBase.locationToDepth(node.getNetworkLocation()) + 1;
     netlock.writeLock().lock();
     try {
+      if ((depthOfAllLeaves != -1) && (depthOfAllLeaves != newDepth)) {
+        LOG.error("Error: can't add leaf node at depth " +
+            newDepth + " to topology:\n" + oldTopoStr);
+        throw new InvalidTopologyException("Invalid network topology. " +
+            "You cannot have a rack and a non-rack node at the same " +
+            "level of the network topology.");
+      }
       Node rack = getNode(node.getNetworkLocation());
       if (rack != null && !(rack instanceof InnerNode)) {
         throw new IllegalArgumentException("Unexpected data node " 
@@ -358,14 +366,6 @@ public class NetworkTopology {
         if (!(node instanceof InnerNode)) {
           if (depthOfAllLeaves == -1) {
             depthOfAllLeaves = node.getLevel();
-          } else {
-            if (depthOfAllLeaves != node.getLevel()) {
-              LOG.error("Error: can't add leaf node at depth " +
-                  node.getLevel() + " to topology:\n" + oldTopoStr);
-              throw new InvalidTopologyException("Invalid network topology. " +
-                  "You cannot have a rack and a non-rack node at the same " +
-                  "level of the network topology.");
-            }
           }
         }
       }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NodeBase.java

@@ -167,4 +167,16 @@ public class NodeBase implements Node {
   public void setLevel(int level) {
     this.level = level;
   }
+  
+  public static int locationToDepth(String location) {
+    String normalizedLocation = normalize(location);
+    int length = normalizedLocation.length();
+    int depth = 0;
+    for (int i = 0; i < length; i++) {
+      if (normalizedLocation.charAt(i) == PATH_SEPARATOR) {
+        depth++;
+      }
+    }
+    return depth;
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/ScriptBasedMapping.java

@@ -263,5 +263,11 @@ public final class ScriptBasedMapping extends CachedDNSToSwitchMapping {
     public String toString() {
       return scriptName != null ? ("script " + scriptName) : NO_SCRIPT;
     }
+
+    @Override
+    public void reloadCachedMappings() {
+      // Nothing to do here, since RawScriptBasedMapping has no cache, and
+      // does not inherit from CachedDNSToSwitchMapping
+    }
   }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/TableMapping.java

@@ -76,20 +76,24 @@ public class TableMapping extends CachedDNSToSwitchMapping {
     getRawMapping().setConf(conf);
   }
   
+  @Override
+  public void reloadCachedMappings() {
+    super.reloadCachedMappings();
+    getRawMapping().reloadCachedMappings();
+  }
+  
   private static final class RawTableMapping extends Configured
       implements DNSToSwitchMapping {
     
-    private final Map<String, String> map = new HashMap<String, String>();
+    private Map<String, String> map;
-    private boolean initialized = false;
   
-    private synchronized void load() {
+    private Map<String, String> load() {
-      map.clear();
+      Map<String, String> loadMap = new HashMap<String, String>();
   
       String filename = getConf().get(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, null);
       if (StringUtils.isBlank(filename)) {
-        LOG.warn(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY + " not configured. "
+        LOG.warn(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY + " not configured. ");
-            + NetworkTopology.DEFAULT_RACK + " will be returned.");
+        return null;
-        return;
       }
   
       BufferedReader reader = null;
@@ -101,7 +105,7 @@ public class TableMapping extends CachedDNSToSwitchMapping {
           if (line.length() != 0 && line.charAt(0) != '#') {
             String[] columns = line.split("\\s+");
             if (columns.length == 2) {
-              map.put(columns[0], columns[1]);
+              loadMap.put(columns[0], columns[1]);
             } else {
               LOG.warn("Line does not have two columns. Ignoring. " + line);
             }
@@ -109,29 +113,31 @@ public class TableMapping extends CachedDNSToSwitchMapping {
           line = reader.readLine();
         }
       } catch (Exception e) {
-        LOG.warn(filename + " cannot be read. " + NetworkTopology.DEFAULT_RACK
+        LOG.warn(filename + " cannot be read.", e);
-            + " will be returned.", e);
+        return null;
-        map.clear();
       } finally {
         if (reader != null) {
           try {
             reader.close();
           } catch (IOException e) {
-            LOG.warn(filename + " cannot be read. "
+            LOG.warn(filename + " cannot be read.", e);
-                + NetworkTopology.DEFAULT_RACK + " will be returned.", e);
+            return null;
-            map.clear();
           }
         }
       }
+      return loadMap;
     }
   
     @Override
     public synchronized List<String> resolve(List<String> names) {
-      if (!initialized) {
+      if (map == null) {
-        initialized = true;
+        map = load();
-        load();
+        if (map == null) {
+          LOG.warn("Failed to read topology table. " +
+            NetworkTopology.DEFAULT_RACK + " will be used for all nodes.");
+          map = new HashMap<String, String>();
+        }
       }
-  
       List<String> results = new ArrayList<String>(names.size());
       for (String name : names) {
         String result = map.get(name);
@@ -143,6 +149,18 @@ public class TableMapping extends CachedDNSToSwitchMapping {
       }
       return results;
     }
-    
+
+    @Override
+    public void reloadCachedMappings() {
+      Map<String, String> newMap = load();
+      if (newMap == null) {
+        LOG.error("Failed to reload the topology table.  The cached " +
+            "mappings will not be cleared.");
+      } else {
+        synchronized(this) {
+          map = newMap;
+        }
+      }
+    }
   }
 }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/StaticMapping.java

@@ -147,4 +147,9 @@ public class StaticMapping extends AbstractDNSToSwitchMapping  {
       nameToRackMap.clear();
     }
   }
+  
+  public void reloadCachedMappings() {
+    // reloadCachedMappings does nothing for StaticMapping; there is
+    // nowhere to reload from since all data is in memory.
+  }
 }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestSwitchMapping.java

@@ -116,5 +116,9 @@ public class TestSwitchMapping extends Assert {
     public List<String> resolve(List<String> names) {
       return names;
     }
+
+    @Override
+    public void reloadCachedMappings() {
+    }
   }
 }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestTableMapping.java

@@ -34,23 +34,17 @@ import org.junit.Before;
 import org.junit.Test;
 
 public class TestTableMapping {
-  
-  private File mappingFile;
-  
-  @Before
-  public void setUp() throws IOException {
-    mappingFile = File.createTempFile(getClass().getSimpleName(), ".txt");
-    Files.write("a.b.c /rack1\n" +
-                "1.2.3.4\t/rack2\n", mappingFile, Charsets.UTF_8);
-    mappingFile.deleteOnExit();
-  }
-
   @Test
   public void testResolve() throws IOException {
+    File mapFile = File.createTempFile(getClass().getSimpleName() +
+        ".testResolve", ".txt");
+    Files.write("a.b.c /rack1\n" +
+                "1.2.3.4\t/rack2\n", mapFile, Charsets.UTF_8);
+    mapFile.deleteOnExit();
     TableMapping mapping = new TableMapping();
 
     Configuration conf = new Configuration();
-    conf.set(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, mappingFile.getCanonicalPath());
+    conf.set(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, mapFile.getCanonicalPath());
     mapping.setConf(conf);
 
     List<String> names = new ArrayList<String>();
@@ -65,10 +59,15 @@ public class TestTableMapping {
 
   @Test
   public void testTableCaching() throws IOException {
+    File mapFile = File.createTempFile(getClass().getSimpleName() +
+        ".testTableCaching", ".txt");
+    Files.write("a.b.c /rack1\n" +
+                "1.2.3.4\t/rack2\n", mapFile, Charsets.UTF_8);
+    mapFile.deleteOnExit();
     TableMapping mapping = new TableMapping();
 
     Configuration conf = new Configuration();
-    conf.set(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, mappingFile.getCanonicalPath());
+    conf.set(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, mapFile.getCanonicalPath());
     mapping.setConf(conf);
 
     List<String> names = new ArrayList<String>();
@@ -123,13 +122,53 @@ public class TestTableMapping {
   }
 
   @Test
-  public void testBadFile() throws IOException {
+  public void testClearingCachedMappings() throws IOException {
-    Files.write("bad contents", mappingFile, Charsets.UTF_8);
+    File mapFile = File.createTempFile(getClass().getSimpleName() +
-    
+        ".testClearingCachedMappings", ".txt");
+    Files.write("a.b.c /rack1\n" +
+                "1.2.3.4\t/rack2\n", mapFile, Charsets.UTF_8);
+    mapFile.deleteOnExit();
+
     TableMapping mapping = new TableMapping();
 
     Configuration conf = new Configuration();
-    conf.set(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, mappingFile.getCanonicalPath());
+    conf.set(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, mapFile.getCanonicalPath());
+    mapping.setConf(conf);
+
+    List<String> names = new ArrayList<String>();
+    names.add("a.b.c");
+    names.add("1.2.3.4");
+
+    List<String> result = mapping.resolve(names);
+    assertEquals(names.size(), result.size());
+    assertEquals("/rack1", result.get(0));
+    assertEquals("/rack2", result.get(1));
+
+    Files.write("", mapFile, Charsets.UTF_8);
+
+    mapping.reloadCachedMappings();
+
+    names = new ArrayList<String>();
+    names.add("a.b.c");
+    names.add("1.2.3.4");
+
+    result = mapping.resolve(names);
+    assertEquals(names.size(), result.size());
+    assertEquals(NetworkTopology.DEFAULT_RACK, result.get(0));
+    assertEquals(NetworkTopology.DEFAULT_RACK, result.get(1));
+  }
+
+
+  @Test(timeout=60000)
+  public void testBadFile() throws IOException {
+    File mapFile = File.createTempFile(getClass().getSimpleName() +
+        ".testBadFile", ".txt");
+    Files.write("bad contents", mapFile, Charsets.UTF_8);
+    mapFile.deleteOnExit();
+    TableMapping mapping = new TableMapping();
+
+    Configuration conf = new Configuration();
+    conf.set(NET_TOPOLOGY_TABLE_MAPPING_FILE_KEY, mapFile.getCanonicalPath());
     mapping.setConf(conf);
 
     List<String> names = new ArrayList<String>();
@@ -141,5 +180,4 @@ public class TestTableMapping {
     assertEquals(result.get(0), NetworkTopology.DEFAULT_RACK);
     assertEquals(result.get(1), NetworkTopology.DEFAULT_RACK);
   }
-
 }

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

@@ -23,6 +23,9 @@ Release 2.0.5-beta - UNRELEASED
     HDFS-4569. Small image transfer related cleanups.
     (Andrew Wang via suresh)
 
+    HDFS-4521. Invalid network toploogies should not be cached. (Colin Patrick
+    McCabe via atm)
+
   OPTIMIZATIONS
 
   BUG FIXES

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

@@ -66,6 +66,7 @@ import org.apache.hadoop.ipc.Server;
 import org.apache.hadoop.net.CachedDNSToSwitchMapping;
 import org.apache.hadoop.net.DNSToSwitchMapping;
 import org.apache.hadoop.net.NetworkTopology;
+import org.apache.hadoop.net.NetworkTopology.InvalidTopologyException;
 import org.apache.hadoop.net.ScriptBasedMapping;
 import org.apache.hadoop.util.Daemon;
 import org.apache.hadoop.util.HostsFileReader;
@@ -418,8 +419,8 @@ public class DatanodeManager {
       host2DatanodeMap.remove(datanodeMap.put(node.getStorageID(), node));
     }
 
+    networktopology.add(node); // may throw InvalidTopologyException
     host2DatanodeMap.add(node);
-    networktopology.add(node);
     checkIfClusterIsNowMultiRack(node);
 
     if (LOG.isDebugEnabled()) {
@@ -634,92 +635,122 @@ public class DatanodeManager {
       nodeReg.setIpAddr(ip);
       nodeReg.setPeerHostName(hostname);
     }
-
-    nodeReg.setExportedKeys(blockManager.getBlockKeys());
-
-    // Checks if the node is not on the hosts list.  If it is not, then
-    // it will be disallowed from registering. 
-    if (!inHostsList(nodeReg)) {
-      throw new DisallowedDatanodeException(nodeReg);
-    }
-      
-    NameNode.stateChangeLog.info("BLOCK* registerDatanode: from "
-        + nodeReg + " storage " + nodeReg.getStorageID());
-
-    DatanodeDescriptor nodeS = datanodeMap.get(nodeReg.getStorageID());
-    DatanodeDescriptor nodeN = host2DatanodeMap.getDatanodeByXferAddr(
-        nodeReg.getIpAddr(), nodeReg.getXferPort());
-      
-    if (nodeN != null && nodeN != nodeS) {
-      NameNode.LOG.info("BLOCK* registerDatanode: " + nodeN);
-      // nodeN previously served a different data storage, 
-      // which is not served by anybody anymore.
-      removeDatanode(nodeN);
-      // physically remove node from datanodeMap
-      wipeDatanode(nodeN);
-      nodeN = null;
-    }
-
-    if (nodeS != null) {
-      if (nodeN == nodeS) {
-        // The same datanode has been just restarted to serve the same data 
-        // storage. We do not need to remove old data blocks, the delta will
-        // be calculated on the next block report from the datanode
-        if(NameNode.stateChangeLog.isDebugEnabled()) {
-          NameNode.stateChangeLog.debug("BLOCK* registerDatanode: "
-              + "node restarted.");
-        }
-      } else {
-        // nodeS is found
-        /* The registering datanode is a replacement node for the existing 
-          data storage, which from now on will be served by a new node.
-          If this message repeats, both nodes might have same storageID 
-          by (insanely rare) random chance. User needs to restart one of the
-          nodes with its data cleared (or user can just remove the StorageID
-          value in "VERSION" file under the data directory of the datanode,
-          but this is might not work if VERSION file format has changed 
-       */        
-        NameNode.stateChangeLog.info("BLOCK* registerDatanode: " + nodeS
-            + " is replaced by " + nodeReg + " with the same storageID "
-            + nodeReg.getStorageID());
-      }
-      // update cluster map
-      getNetworkTopology().remove(nodeS);
-      nodeS.updateRegInfo(nodeReg);
-      nodeS.setDisallowed(false); // Node is in the include list
-      
-      // resolve network location
-      resolveNetworkLocation(nodeS);
-      getNetworkTopology().add(nodeS);
-        
-      // also treat the registration message as a heartbeat
-      heartbeatManager.register(nodeS);
-      checkDecommissioning(nodeS);
-      return;
-    } 
-
-    // this is a new datanode serving a new data storage
-    if ("".equals(nodeReg.getStorageID())) {
-      // this data storage has never been registered
-      // it is either empty or was created by pre-storageID version of DFS
-      nodeReg.setStorageID(newStorageID());
-      if (NameNode.stateChangeLog.isDebugEnabled()) {
-        NameNode.stateChangeLog.debug(
-            "BLOCK* NameSystem.registerDatanode: "
-            + "new storageID " + nodeReg.getStorageID() + " assigned.");
-      }
-    }
-    // register new datanode
-    DatanodeDescriptor nodeDescr 
-      = new DatanodeDescriptor(nodeReg, NetworkTopology.DEFAULT_RACK);
-    resolveNetworkLocation(nodeDescr);
-    addDatanode(nodeDescr);
-    checkDecommissioning(nodeDescr);
     
-    // also treat the registration message as a heartbeat
+    try {
-    // no need to update its timestamp
+      nodeReg.setExportedKeys(blockManager.getBlockKeys());
-    // because its is done when the descriptor is created
+  
-    heartbeatManager.addDatanode(nodeDescr);
+      // Checks if the node is not on the hosts list.  If it is not, then
+      // it will be disallowed from registering. 
+      if (!inHostsList(nodeReg)) {
+        throw new DisallowedDatanodeException(nodeReg);
+      }
+        
+      NameNode.stateChangeLog.info("BLOCK* registerDatanode: from "
+          + nodeReg + " storage " + nodeReg.getStorageID());
+  
+      DatanodeDescriptor nodeS = datanodeMap.get(nodeReg.getStorageID());
+      DatanodeDescriptor nodeN = host2DatanodeMap.getDatanodeByXferAddr(
+          nodeReg.getIpAddr(), nodeReg.getXferPort());
+        
+      if (nodeN != null && nodeN != nodeS) {
+        NameNode.LOG.info("BLOCK* registerDatanode: " + nodeN);
+        // nodeN previously served a different data storage, 
+        // which is not served by anybody anymore.
+        removeDatanode(nodeN);
+        // physically remove node from datanodeMap
+        wipeDatanode(nodeN);
+        nodeN = null;
+      }
+  
+      if (nodeS != null) {
+        if (nodeN == nodeS) {
+          // The same datanode has been just restarted to serve the same data 
+          // storage. We do not need to remove old data blocks, the delta will
+          // be calculated on the next block report from the datanode
+          if(NameNode.stateChangeLog.isDebugEnabled()) {
+            NameNode.stateChangeLog.debug("BLOCK* registerDatanode: "
+                + "node restarted.");
+          }
+        } else {
+          // nodeS is found
+          /* The registering datanode is a replacement node for the existing 
+            data storage, which from now on will be served by a new node.
+            If this message repeats, both nodes might have same storageID 
+            by (insanely rare) random chance. User needs to restart one of the
+            nodes with its data cleared (or user can just remove the StorageID
+            value in "VERSION" file under the data directory of the datanode,
+            but this is might not work if VERSION file format has changed 
+         */        
+          NameNode.stateChangeLog.info("BLOCK* registerDatanode: " + nodeS
+              + " is replaced by " + nodeReg + " with the same storageID "
+              + nodeReg.getStorageID());
+        }
+        
+        boolean success = false;
+        try {
+          // update cluster map
+          getNetworkTopology().remove(nodeS);
+          nodeS.updateRegInfo(nodeReg);
+          nodeS.setDisallowed(false); // Node is in the include list
+          
+          // resolve network location
+          resolveNetworkLocation(nodeS);
+          getNetworkTopology().add(nodeS);
+            
+          // also treat the registration message as a heartbeat
+          heartbeatManager.register(nodeS);
+          checkDecommissioning(nodeS);
+          success = true;
+        } finally {
+          if (!success) {
+            removeDatanode(nodeS);
+            wipeDatanode(nodeS);
+          }
+        }
+        return;
+      } 
+  
+      // this is a new datanode serving a new data storage
+      if ("".equals(nodeReg.getStorageID())) {
+        // this data storage has never been registered
+        // it is either empty or was created by pre-storageID version of DFS
+        nodeReg.setStorageID(newStorageID());
+        if (NameNode.stateChangeLog.isDebugEnabled()) {
+          NameNode.stateChangeLog.debug(
+              "BLOCK* NameSystem.registerDatanode: "
+              + "new storageID " + nodeReg.getStorageID() + " assigned.");
+        }
+      }
+      
+      DatanodeDescriptor nodeDescr 
+        = new DatanodeDescriptor(nodeReg, NetworkTopology.DEFAULT_RACK);
+      boolean success = false;
+      try {
+        resolveNetworkLocation(nodeDescr);
+        networktopology.add(nodeDescr);
+  
+        // register new datanode
+        addDatanode(nodeDescr);
+        checkDecommissioning(nodeDescr);
+        
+        // also treat the registration message as a heartbeat
+        // no need to update its timestamp
+        // because its is done when the descriptor is created
+        heartbeatManager.addDatanode(nodeDescr);
+        success = true;
+      } finally {
+        if (!success) {
+          removeDatanode(nodeDescr);
+          wipeDatanode(nodeDescr);
+        }
+      }
+    } catch (InvalidTopologyException e) {
+      // If the network location is invalid, clear the cached mappings
+      // so that we have a chance to re-add this DataNode with the
+      // correct network location later.
+      dnsToSwitchMapping.reloadCachedMappings();
+      throw e;
+    }
   }
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/net/TestNetworkTopology.java

@@ -26,12 +26,23 @@ import static org.junit.Assert.fail;
 import java.util.HashMap;
 import java.util.Map;
 
+import junit.framework.Assert;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.DFSTestUtil;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
+import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
+import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
 import org.junit.Before;
 import org.junit.Test;
 
 public class TestNetworkTopology {
+  private static final Log LOG = LogFactory.getLog(TestNetworkTopology.class);
   private final static NetworkTopology cluster = new NetworkTopology();
   private DatanodeDescriptor dataNodes[];
   
@@ -213,4 +224,65 @@ public class TestNetworkTopology {
       }
     }
   }
+
+  @Test(timeout=180000)
+  public void testInvalidNetworkTopologiesNotCachedInHdfs() throws Exception {
+    // start a cluster
+    Configuration conf = new HdfsConfiguration();
+    MiniDFSCluster cluster = null;
+    try {
+      // bad rack topology
+      String racks[] = { "/a/b", "/c" };
+      String hosts[] = { "foo1.example.com", "foo2.example.com" };
+      cluster = new MiniDFSCluster.Builder(conf).numDataNodes(2).
+          racks(racks).hosts(hosts).build();
+      cluster.waitActive();
+      
+      NamenodeProtocols nn = cluster.getNameNodeRpc();
+      Assert.assertNotNull(nn);
+      
+      // Wait for one DataNode to register.
+      // The other DataNode will not be able to register up because of the rack mismatch.
+      DatanodeInfo[] info;
+      while (true) {
+        info = nn.getDatanodeReport(DatanodeReportType.LIVE);
+        Assert.assertFalse(info.length == 2);
+        if (info.length == 1) {
+          break;
+        }
+        Thread.sleep(1000);
+      }
+      // Set the network topology of the other node to the match the network
+      // topology of the node that came up.
+      int validIdx = info[0].getHostName().equals(hosts[0]) ? 0 : 1;
+      int invalidIdx = validIdx == 1 ? 0 : 1;
+      StaticMapping.addNodeToRack(hosts[invalidIdx], racks[validIdx]);
+      LOG.info("datanode " + validIdx + " came up with network location " + 
+        info[0].getNetworkLocation());
+
+      // Restart the DN with the invalid topology and wait for it to register.
+      cluster.restartDataNode(invalidIdx);
+      Thread.sleep(5000);
+      while (true) {
+        info = nn.getDatanodeReport(DatanodeReportType.LIVE);
+        if (info.length == 2) {
+          break;
+        }
+        if (info.length == 0) {
+          LOG.info("got no valid DNs");
+        } else if (info.length == 1) {
+          LOG.info("got one valid DN: " + info[0].getHostName() +
+              " (at " + info[0].getNetworkLocation() + ")");
+        }
+        Thread.sleep(1000);
+      }
+      Assert.assertEquals(info[0].getNetworkLocation(),
+                          info[1].getNetworkLocation());
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+    }
+  }
+
 }

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/test/java/org/apache/hadoop/mapreduce/v2/hs/TestJobHistoryParsing.java

@@ -83,6 +83,10 @@ public class TestJobHistoryParsing {
     public List<String> resolve(List<String> names) {
       return Arrays.asList(new String[]{RACK_NAME});
     }
+
+    @Override
+    public void reloadCachedMappings() {
+    }
   }
 
   @Test

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestRackResolver.java

@@ -63,6 +63,10 @@ public class TestRackResolver {
       return returnList;
     }
 
+    @Override
+    public void reloadCachedMappings() {
+      // nothing to do here, since RawScriptBasedMapping has no cache.
+    }
   }
 
   @Test