HDFS-2825. Add test hook to turn off the writer preferring its local DN. Contributed by Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1235025 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -290,6 +290,9 @@ Release 0.23.1 - UNRELEASED
     for a client on the same node as the block file.  (Andrew Purtell,
     Suresh Srinivas and Jitendra Nath Pandey via szetszwo)
 
+    HDFS-2825. Add test hook to turn off the writer preferring its local
+    DN. (todd)
+
   BUG FIXES
 
     HDFS-2541. For a sufficiently large value of blocks, the DN Scanner 

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

@@ -38,6 +38,8 @@ import org.apache.hadoop.net.NetworkTopology;
 import org.apache.hadoop.net.Node;
 import org.apache.hadoop.net.NodeBase;
 
+import com.google.common.annotations.VisibleForTesting;
+
 /** The class is responsible for choosing the desired number of targets
  * for placing block replicas.
  * The replica placement strategy is that if the writer is on a datanode,
@@ -49,6 +51,7 @@ import org.apache.hadoop.net.NodeBase;
 @InterfaceAudience.Private
 public class BlockPlacementPolicyDefault extends BlockPlacementPolicy {
   private boolean considerLoad; 
+  private boolean preferLocalNode = true;
   private NetworkTopology clusterMap;
   private FSClusterStats stats;
   static final String enableDebugLogging = "For more information, please enable"
@@ -223,17 +226,17 @@ public class BlockPlacementPolicyDefault extends BlockPlacementPolicy {
     if (localMachine == null)
       return chooseRandom(NodeBase.ROOT, excludedNodes, 
                           blocksize, maxNodesPerRack, results);
-      
-    // otherwise try local machine first
-    Node oldNode = excludedNodes.put(localMachine, localMachine);
-    if (oldNode == null) { // was not in the excluded list
-      if (isGoodTarget(localMachine, blocksize,
-                       maxNodesPerRack, false, results)) {
-        results.add(localMachine);
-        return localMachine;
-      }
-    } 
-      
+    if (preferLocalNode) {
+      // otherwise try local machine first
+      Node oldNode = excludedNodes.put(localMachine, localMachine);
+      if (oldNode == null) { // was not in the excluded list
+        if (isGoodTarget(localMachine, blocksize,
+                         maxNodesPerRack, false, results)) {
+          results.add(localMachine);
+          return localMachine;
+        }
+      } 
+    }      
     // try a node on local rack
     return chooseLocalRack(localMachine, excludedNodes, 
                            blocksize, maxNodesPerRack, results);
@@ -568,5 +571,10 @@ public class BlockPlacementPolicyDefault extends BlockPlacementPolicy {
     }
     return cur;
   }
+  
+  @VisibleForTesting
+  void setPreferLocalNode(boolean prefer) {
+    this.preferLocalNode = prefer;
+  }
 }
 

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

@@ -27,6 +27,8 @@ import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.util.Daemon;
 
+import com.google.common.base.Preconditions;
+
 public class BlockManagerTestUtil {
   public static void setNodeReplicationLimit(final BlockManager blockManager,
       final int limit) {
@@ -122,4 +124,17 @@ public class BlockManagerTestUtil {
     return blockManager.computeDatanodeWork();
   }
   
+  
+  /**
+   * Change whether the block placement policy will prefer the writer's
+   * local Datanode or not.
+   * @param prefer
+   */
+  public static void setWritingPrefersLocalNode(
+      BlockManager bm, boolean prefer) {
+    BlockPlacementPolicy bpp = bm.getBlockPlacementPolicy();
+    Preconditions.checkState(bpp instanceof BlockPlacementPolicyDefault,
+        "Must use default policy, got %s", bpp.getClass());
+    ((BlockPlacementPolicyDefault)bpp).setPreferLocalNode(prefer);
+  }
 }