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源码分析-NN启动(一)

2021-07-25 19:08:01 星期日  阅读：1187

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 #### NameNode工作机制  #### NameNode启动源码梳理  #### NameNode初始化关键源码展示 NameNode启动的main方法 ``` public static void main(String argv[]) throws Exception { if (DFSUtil.parseHelpArgument(argv, NameNode.USAGE, System.out, true)) { System.exit(0); } try { StringUtils.startupShutdownMessage(NameNode.class, argv, LOG); // 创建 NameNode NameNode namenode = createNameNode(argv, null); if (namenode != null) { namenode.join(); } } catch (Throwable e) { LOG.error("Failed to start namenode.", e); terminate(1, e); } } ``` createNameNode方法 ``` public static NameNode createNameNode(String argv[], Configuration conf) throws IOException { ...... StartupOption startOpt = parseArguments(argv); if (startOpt == null) { printUsage(System.err); return null; } setStartupOption(conf, startOpt); boolean aborted = false; switch (startOpt) { case FORMAT: aborted = format(conf, startOpt.getForceFormat(), startOpt.getInteractiveFormat()); terminate(aborted ? 1 : 0); return null; // avoid javac warning case GENCLUSTERID: ......default: DefaultMetricsSystem.initialize("NameNode"); // 创建 NameNode 对象 return new NameNode(conf); } } ``` NameNode对象 ```java public NameNode(Configuration conf) throws IOException { this(conf, NamenodeRole.NAMENODE); } protected NameNode(Configuration conf, NamenodeRole role) throws IOException { ... ... try { initializeGenericKeys(conf, nsId, namenodeId); initialize(getConf()); ... ... } catch (IOException e) { this.stopAtException(e); throw e; } catch (HadoopIllegalArgumentException e) { this.stopAtException(e); throw e; } this.started.set(true); } ``` NameNode对象初始化 ```java protected void initialize(Configuration conf) throws IOException { ... ... if (NamenodeRole.NAMENODE == role) { // 启动 HTTP 服务端(9870) startHttpServer(conf); } // 加载镜像文件和编辑日志到内存 loadNamesystem(conf); startAliasMapServerIfNecessary(conf); // 创建NN的RPC服务端 rpcServer = createRpcServer(conf); initReconfigurableBackoffKey(); if (clientNamenodeAddress == null) { // This is expected for MiniDFSCluster. Set it now using // the RPC server"s bind address. clientNamenodeAddress = NetUtils.getHostPortString(getNameNodeAddress()); LOG.info("Clients are to use " + clientNamenodeAddress + " to access" + " this namenode/service."); } if (NamenodeRole.NAMENODE == role) { httpServer.setNameNodeAddress(getNameNodeAddress()); httpServer.setFSImage(getFSImage()); } // NN 启动资源检查 startCommonServices(conf); startMetricsLogger(conf); } ``` 参考文章：[尚硅谷官网](http://www.atguigu.com/)