RPC源码阅读-交互协议

package org.apache.hadoop.ipc;

import java.io.IOException;

/**
 * Superclass of all protocols that use Hadoop RPC.
 * Subclasses of this interface are also supposed to have
 * a static final long versionID field.
 */
public interface VersionedProtocol {
  
  /**
   * Return protocol version corresponding to protocol interface.
   * @param protocol The classname of the protocol interface
   * @param clientVersion The version of the protocol that the client speaks
   * @return the version that the server will speak
   * @throws IOException if any IO error occurs
   */
  public long getProtocolVersion(String protocol,
                                 long clientVersion) throws IOException;

  /**
   * Return protocol version corresponding to protocol interface.
   * @param protocol The classname of the protocol interface
   * @param clientVersion The version of the protocol that the client speaks
   * @param clientMethodsHash the hashcode of client protocol methods
   * @return the server protocol signature containing its version and
   *         a list of its supported methods
   * @see ProtocolSignature#getProtocolSignature(VersionedProtocol, String, 
   *                long, int) for a default implementation
   */
  public ProtocolSignature getProtocolSignature(String protocol, 
                                 long clientVersion,
                                 int clientMethodsHash) throws IOException;
}

ClientDatanodeProtocol ：一个客户端和datanode之间的协议接口，用于数据块恢复
ClientProtocol ：client与Namenode交互的接口，所有控制流的请求均在这里，如：创建文件、删除文件等；
DatanodeProtocol : Datanode与Namenode交互的接口，如心跳、blockreport等；
NamenodeProtocol ：SecondaryNode与Namenode交互的接口。

InterDatanodeProtocol ：Datanode内部交互的接口，用来更新block的元数据；
InnerTrackerProtocol ：TaskTracker与JobTracker交互的接口，功能与DatanodeProtocol相似；//在hadoop2.6中找不到
JobSubmissionProtocol ：JobClient与JobTracker交互的接口，用来提交Job、获得Job等与Job相关的操作；//在hadoop2.6中找不到
TaskUmbilicalProtocol ：Task中子进程与母进程交互的接口，子进程即map、reduce等操作，母进程即TaskTracker，该接口可以回报子进程的运行状态（词汇扫盲: umbilical 脐带的, 关系亲密的） 。