HDFS-4099. Clean up replication code and add more javadoc.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1400986 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -408,6 +408,8 @@ Release 2.0.3-alpha - Unreleased
     HDFS-4088. Remove "throws QuotaExceededException" from an
     INodeDirectoryWithQuota constructor. (szetszwo)
 
+    HDFS-4099. Clean up replication code and add more javadoc. (szetszwo)
+
   OPTIMIZATIONS
 
   BUG FIXES

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

@@ -17,6 +17,8 @@
  */
 package org.apache.hadoop.hdfs.server.blockmanagement;
 
+import static org.apache.hadoop.util.ExitUtil.terminate;
+
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.ArrayList;
@@ -49,14 +51,11 @@ import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.UnregisteredNodeException;
-import org.apache.hadoop.hdfs.security.token.block.DataEncryptionKey;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager.AccessMode;
+import org.apache.hadoop.hdfs.security.token.block.DataEncryptionKey;
 import org.apache.hadoop.hdfs.security.token.block.ExportedBlockKeys;
 import org.apache.hadoop.hdfs.server.blockmanagement.PendingDataNodeMessages.ReportedBlockInfo;
-
-import static org.apache.hadoop.util.ExitUtil.terminate;
-
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.BlockUCState;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
 import org.apache.hadoop.hdfs.server.namenode.FSClusterStats;
@@ -2833,28 +2832,32 @@ assert storedBlock.findDatanode(dn) < 0 : "Block " + block
     }
   }
 
-  public void checkReplication(Block block, short numExpectedReplicas) {
-    // filter out containingNodes that are marked for decommission.
-    NumberReplicas number = countNodes(block);
-    if (isNeededReplication(block, numExpectedReplicas, number.liveReplicas())) { 
-      neededReplications.add(block,
-                             number.liveReplicas(),
-                             number.decommissionedReplicas(),
-                             numExpectedReplicas);
-      return;
-    }
-    if (number.liveReplicas() > numExpectedReplicas) {
-      processOverReplicatedBlock(block, numExpectedReplicas, null, null);
+  /**
+   * Check replication of the blocks in the collection.
+   * If any block is needed replication, insert it into the replication queue.
+   * Otherwise, if the block is more than the expected replication factor,
+   * process it as an over replicated block.
+   */
+  public void checkReplication(BlockCollection bc) {
+    final short expected = bc.getBlockReplication();
+    for (Block block : bc.getBlocks()) {
+      final NumberReplicas n = countNodes(block);
+      if (isNeededReplication(block, expected, n.liveReplicas())) { 
+        neededReplications.add(block, n.liveReplicas(),
+            n.decommissionedReplicas(), expected);
+      } else if (n.liveReplicas() > expected) {
+        processOverReplicatedBlock(block, expected, null, null);
+      }
     }
   }
 
-  /* get replication factor of a block */
+  /** 
+   * @return 0 if the block is not found;
+   *         otherwise, return the replication factor of the block.
+   */
   private int getReplication(Block block) {
-    BlockCollection bc = blocksMap.getBlockCollection(block);
-    if (bc == null) { // block does not belong to any file
-      return 0;
-    }
-    return bc.getBlockReplication();
+    final BlockCollection bc = blocksMap.getBlockCollection(block);
+    return bc == null? 0: bc.getBlockReplication();
   }
 
 
@@ -2929,12 +2932,12 @@ assert storedBlock.findDatanode(dn) < 0 : "Block " + block
     return enoughRacks;
   }
 
-  boolean isNeededReplication(Block b, int expectedReplication, int curReplicas) {
-    if ((curReplicas >= expectedReplication) && (blockHasEnoughRacks(b))) {
-      return false;
-    } else {
-      return true;
-    }
+  /**
+   * A block needs replication if the number of replicas is less than expected
+   * or if it does not have enough racks.
+   */
+  private boolean isNeededReplication(Block b, int expected, int current) {
+    return current < expected || !blockHasEnoughRacks(b);
   }
   
   public long getMissingBlocksCount() {

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

@@ -2428,21 +2428,6 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
     return true;
   }
 
-  /** 
-   * Check all blocks of a file. If any blocks are lower than their intended
-   * replication factor, then insert them into neededReplication and if 
-   * the blocks are more than the intended replication factor then insert 
-   * them into invalidateBlocks.
-   */
-  private void checkReplicationFactor(INodeFile file) {
-    short numExpectedReplicas = file.getBlockReplication();
-    Block[] pendingBlocks = file.getBlocks();
-    int nrBlocks = pendingBlocks.length;
-    for (int i = 0; i < nrBlocks; i++) {
-      blockManager.checkReplication(pendingBlocks[i], numExpectedReplicas);
-    }
-  }
-    
   /**
    * Allocate a block at the given pending filename
    * 
@@ -3175,7 +3160,7 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
     // close file and persist block allocations for this file
     dir.closeFile(src, newFile);
 
-    checkReplicationFactor(newFile);
+    blockManager.checkReplication(newFile);
   }
 
   void commitBlockSynchronization(ExtendedBlock lastblock,