HDFS-13418. NetworkTopology should be configurable when enable DFSNetworkTopology. Contributed by Tao Jie.

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

@@ -21,6 +21,7 @@ package org.apache.hadoop.hdfs;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
+import org.apache.hadoop.hdfs.net.DFSNetworkTopology;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.RamDiskReplicaLruTracker;
@@ -1003,6 +1004,12 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
       "dfs.use.dfs.network.topology";
   public static final boolean DFS_USE_DFS_NETWORK_TOPOLOGY_DEFAULT = true;
 
+  public static final String DFS_NET_TOPOLOGY_IMPL_KEY =
+      "dfs.net.topology.impl";
+
+  public static final Class<DFSNetworkTopology> DFS_NET_TOPOLOGY_IMPL_DEFAULT =
+      DFSNetworkTopology.class;
+
   // dfs.client.retry confs are moved to HdfsClientConfigKeys.Retry 
   @Deprecated
   public static final String  DFS_CLIENT_RETRY_POLICY_ENABLED_KEY

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/net/DFSNetworkTopology.java

@@ -22,11 +22,13 @@ import com.google.common.base.Preconditions;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.StorageType;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
 import org.apache.hadoop.net.NetworkTopology;
 import org.apache.hadoop.net.Node;
 import org.apache.hadoop.net.NodeBase;
+import org.apache.hadoop.util.ReflectionUtils;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -44,8 +46,11 @@ public class DFSNetworkTopology extends NetworkTopology {
   private static final Random RANDOM = new Random();
 
   public static DFSNetworkTopology getInstance(Configuration conf) {
-    DFSNetworkTopology nt = new DFSNetworkTopology();
+    DFSNetworkTopology nt = ReflectionUtils.newInstance(conf.getClass(
-    return (DFSNetworkTopology)nt.init(DFSTopologyNodeImpl.FACTORY);
+        DFSConfigKeys.DFS_NET_TOPOLOGY_IMPL_KEY,
+        DFSConfigKeys.DFS_NET_TOPOLOGY_IMPL_DEFAULT,
+        DFSNetworkTopology.class), conf);
+    return (DFSNetworkTopology) nt.init(DFSTopologyNodeImpl.FACTORY);
   }
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -4360,6 +4360,20 @@
     <value>true</value>
     <description>
      Enables DFSNetworkTopology to choose nodes for placing replicas.
+      When enabled, NetworkTopology will be instantiated as class defined in
+      property dfs.net.topology.impl, otherwise NetworkTopology will be
+      instantiated as class defined in property net.topology.impl.
+    </description>
+  </property>
+
+  <property>
+    <name>dfs.net.topology.impl</name>
+    <value>org.apache.hadoop.hdfs.net.DFSNetworkTopology</value>
+    <description>
+      The implementation class of NetworkTopology used in HDFS. By default,
+      the class org.apache.hadoop.hdfs.net.DFSNetworkTopology is specified and
+      used in block placement.
+      This property only works when dfs.use.dfs.network.topology is true.
     </description>
   </property>
 

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

@@ -40,6 +40,8 @@ import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
 import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.net.DFSNetworkTopology;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
@@ -52,11 +54,13 @@ import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
 import org.apache.hadoop.hdfs.server.common.StorageInfo;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeRegistration;
 import org.apache.hadoop.net.DNSToSwitchMapping;
+import org.apache.hadoop.net.NetworkTopology;
 import org.apache.hadoop.util.Shell;
 import org.junit.Assert;
 import org.junit.Test;
 import org.mockito.Mockito;
 import org.mockito.internal.util.reflection.Whitebox;
+
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.*;
 
@@ -491,4 +495,52 @@ public class TestDatanodeManager {
     Assert.assertEquals("Unexpected host or host in unexpected position",
         "127.0.0.1:23456", bothAgain.get(1).getInfoAddr());
   }
+
+  @Test
+  public void testNetworkTopologyInstantiation() throws Exception {
+    // case 1, dfs.use.dfs.network.topology=true, use the default
+    // DFSNetworkTopology impl.
+    Configuration conf1 = new HdfsConfiguration();
+    FSNamesystem fsn = Mockito.mock(FSNamesystem.class);
+    DatanodeManager dm1 = mockDatanodeManager(fsn, conf1);
+    assertEquals(DFSNetworkTopology.class, dm1.getNetworkTopology().getClass());
+
+    // case 2, dfs.use.dfs.network.topology=false, use the default
+    // NetworkTopology impl.
+    Configuration conf2 = new HdfsConfiguration();
+    conf2.setBoolean(DFSConfigKeys.DFS_USE_DFS_NETWORK_TOPOLOGY_KEY, false);
+    DatanodeManager dm2 = mockDatanodeManager(fsn, conf2);
+    assertEquals(NetworkTopology.class, dm2.getNetworkTopology()
+        .getClass());
+
+    // case 3, dfs.use.dfs.network.topology=false, and specify the
+    // net.topology.impl property.
+    Configuration conf3 = new HdfsConfiguration();
+    conf3.setClass(CommonConfigurationKeysPublic.NET_TOPOLOGY_IMPL_KEY,
+        MockDfsNetworkTopology.class, NetworkTopology.class);
+    conf3.setBoolean(DFSConfigKeys.DFS_USE_DFS_NETWORK_TOPOLOGY_KEY, false);
+    DatanodeManager dm3 = mockDatanodeManager(fsn, conf3);
+    assertEquals(MockDfsNetworkTopology.class, dm3.getNetworkTopology()
+        .getClass());
+
+    // case 4, dfs.use.dfs.network.topology=true, and specify the
+    // dfs.net.topology.impl property.
+    Configuration conf4 = new HdfsConfiguration();
+    conf4.setClass(DFSConfigKeys.DFS_NET_TOPOLOGY_IMPL_KEY,
+        MockDfsNetworkTopology.class, NetworkTopology.class);
+    conf4.setBoolean(DFSConfigKeys.DFS_USE_DFS_NETWORK_TOPOLOGY_KEY, true);
+    DatanodeManager dm4 = mockDatanodeManager(fsn, conf4);
+    assertEquals(MockDfsNetworkTopology.class, dm4.getNetworkTopology()
+        .getClass());
+  }
+
+  /**
+   * A NetworkTopology implementation for test.
+   *
+   */
+  public static class MockDfsNetworkTopology extends DFSNetworkTopology {
+    public MockDfsNetworkTopology(){
+      super();
+    }
+  }
 }