001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hdfs.server.protocol;
019
020import java.io.DataInput;
021import java.io.DataOutput;
022import java.io.IOException;
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.classification.InterfaceStability;
026import org.apache.hadoop.io.Writable;
027import org.apache.hadoop.io.WritableFactory;
028import org.apache.hadoop.io.WritableFactories;
029import org.apache.hadoop.io.WritableUtils;
030import org.apache.avro.reflect.Union;
031
032/**
033 * Base class for data-node command.
034 * Issued by the name-node to notify data-nodes what should be done.
035 */
036
037// Declare subclasses for Avro's denormalized representation
038@Union({Void.class,
039      DatanodeCommand.Register.class, DatanodeCommand.Finalize.class,
040      BlockCommand.class, UpgradeCommand.class,
041      BlockRecoveryCommand.class, KeyUpdateCommand.class})
042
043@InterfaceAudience.Private
044@InterfaceStability.Evolving
045public abstract class DatanodeCommand extends ServerCommand {
046  static class Register extends DatanodeCommand {
047    private Register() {super(DatanodeProtocol.DNA_REGISTER);}
048    public void readFields(DataInput in) {}
049    public void write(DataOutput out) {}
050  }
051
052  public static class Finalize extends DatanodeCommand {
053    String blockPoolId;
054    private Finalize() {
055      super(DatanodeProtocol.DNA_FINALIZE);
056    }
057    
058    public Finalize(String bpid) {
059      super(DatanodeProtocol.DNA_FINALIZE);
060      blockPoolId = bpid;
061    }
062    
063    public String getBlockPoolId() {
064      return blockPoolId;
065    }
066    
067    public void readFields(DataInput in) throws IOException {
068      blockPoolId = WritableUtils.readString(in);
069    }
070    public void write(DataOutput out) throws IOException {
071      WritableUtils.writeString(out, blockPoolId);
072    }
073  }
074
075  static {                                      // register a ctor
076    WritableFactories.setFactory(Register.class,
077        new WritableFactory() {
078          public Writable newInstance() {return new Register();}
079        });
080    WritableFactories.setFactory(Finalize.class,
081        new WritableFactory() {
082          public Writable newInstance() {return new Finalize();}
083        });
084  }
085
086  public static final DatanodeCommand REGISTER = new Register();
087  
088  public DatanodeCommand() {
089    super();
090  }
091  
092  DatanodeCommand(int action) {
093    super(action);
094  }
095}