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