hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/RegisterCommand.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 org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

/**
 * A RegisterCommand is an instruction to a datanode to register with the namenode.
 * This command can't be combined with other commands in the same response.
 * This is because after the datanode processes RegisterCommand, it will skip
 * the rest of the DatanodeCommands in the same HeartbeatResponse.
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class RegisterCommand extends DatanodeCommand {
  
  public static final DatanodeCommand REGISTER = new RegisterCommand();

  public RegisterCommand() {
    super(DatanodeProtocol.DNA_REGISTER);
  }
}