Hadoop学习二十九：Hadoop-hdfs NameNode源码 成员变量

xiyou

一. NameNode概述
　　* The NameNode controls two critical tables:
 *   1)  filename->blocksequence (namespace)
 *   2)  block->machinelist ("inodes")
 *
 * The first table is stored on disk and is very precious.
 * The second table is rebuilt every time the NameNode comes
 * up.

• 上面这段其实就和FSNameSystem作用一样，因为NameNode的功能基本就是靠FSNameSystem实现的。
  
• 当然，同DataNode一样，NameNode也是一个RPC Server。
  
• NameNode也要提供Http服务。
  

二. NameNode成员变量

  //一个文件系统  一个NameNode 一个FSNamesystem 一个FSDirectory
public FSNamesystem namesystem; // TODO: This should private. Use getNamesystem() instead.
//BackupNode, Datanodes and all other services与serviceRpcServer通信
private Server serviceRpcServer;
//Clients 与server通信
private Server server;
//serviceRpcServer ip port
protected InetSocketAddress serviceRPCAddress = null;
//server ip port
private InetSocketAddress serverAddress = null;
//NameNode可以提供http服务
private HttpServer httpServer;
//http服务 ip port
private InetSocketAddress httpAddress = null;
//暂时不知道做什么  后面看把
private Thread emptier;