/**
 * 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.protocol;


/**
 * 
 * The Client transfers data to/from datanode using a streaming protocol.
 *
 */
public interface DataTransferProtocol {
  
  
  /** Version for data transfers between clients and datanodes
   * This should change when serialization of DatanodeInfo, not just
   * when protocol changes. It is not very obvious. 
   */
  /*
   * Version 14:
   *    OP_REPLACE_BLOCK is sent from the Balancer server to the destination,
   *    including the block id, source, and proxy.
   *    OP_COPY_BLOCK is sent from the destination to the proxy, which contains
   *    only the block id.
   *    A reply to OP_COPY_BLOCK sends the block content.
   *    A reply to OP_REPLACE_BLOCK includes an operation status.
   */
  public static final int DATA_TRANSFER_VERSION = 14;

  // Processed at datanode stream-handler
  public static final byte OP_WRITE_BLOCK = (byte) 80;
  public static final byte OP_READ_BLOCK = (byte) 81;
  public static final byte OP_READ_METADATA = (byte) 82;
  public static final byte OP_REPLACE_BLOCK = (byte) 83;
  public static final byte OP_COPY_BLOCK = (byte) 84;
  public static final byte OP_BLOCK_CHECKSUM = (byte) 85;
  
  public static final int OP_STATUS_SUCCESS = 0;  
  public static final int OP_STATUS_ERROR = 1;  
  public static final int OP_STATUS_ERROR_CHECKSUM = 2;  
  public static final int OP_STATUS_ERROR_INVALID = 3;  
  public static final int OP_STATUS_ERROR_EXISTS = 4;  
  public static final int OP_STATUS_CHECKSUM_OK = 5;  

  public static final int CLIENT_HEARTBEAT_VERSION = 19;

}