branch-2.0.4-alpha/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/BlockCommand.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hdfs.server.protocol;

import java.util.List;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.BlockTargetPair;

/****************************************************
 * A BlockCommand is an instruction to a datanode 
 * regarding some blocks under its control.  It tells
 * the DataNode to either invalidate a set of indicated
 * blocks, or to copy a set of indicated blocks to 
 * another DataNode.
 * 
 ****************************************************/
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class BlockCommand extends DatanodeCommand {
  
  /**
   * This constant is used to indicate that the block deletion does not need
   * explicit ACK from the datanode. When a block is put into the list of blocks
   * to be deleted, it's size is set to this constant. We assume that no block
   * would actually have this size. Otherwise, we would miss ACKs for blocks
   * with such size. Positive number is used for compatibility reasons.
   */
  public static final long NO_ACK = Long.MAX_VALUE;
  
  String poolId;
  Block blocks[];
  DatanodeInfo targets[][];

  /**
   * Create BlockCommand for transferring blocks to another datanode
   * @param blocktargetlist    blocks to be transferred 
   */
  public BlockCommand(int action, String poolId,
      List<BlockTargetPair> blocktargetlist) {
    super(action);
    this.poolId = poolId;
    blocks = new Block[blocktargetlist.size()]; 
    targets = new DatanodeInfo[blocks.length][];
    for(int i = 0; i < blocks.length; i++) {
      BlockTargetPair p = blocktargetlist.get(i);
      blocks[i] = p.block;
      targets[i] = p.targets;
    }
  }

  private static final DatanodeInfo[][] EMPTY_TARGET = {};

  /**
   * Create BlockCommand for the given action
   * @param blocks blocks related to the action
   */
  public BlockCommand(int action, String poolId, Block blocks[]) {
    this(action, poolId, blocks, EMPTY_TARGET);
  }

  /**
   * Create BlockCommand for the given action
   * @param blocks blocks related to the action
   */
  public BlockCommand(int action, String poolId, Block[] blocks,
      DatanodeInfo[][] targets) {
    super(action);
    this.poolId = poolId;
    this.blocks = blocks;
    this.targets = targets;
  }
  
  public String getBlockPoolId() {
    return poolId;
  }
  
  public Block[] getBlocks() {
    return blocks;
  }

  public DatanodeInfo[][] getTargets() {
    return targets;
  }
}