diff --git a/hdfs/nameNode启动过程.md b/hdfs/nameNode启动过程.md new file mode 100644 index 0000000..da873ef --- /dev/null +++ b/hdfs/nameNode启动过程.md @@ -0,0 +1,234 @@ + +# 简介 + +本章详细介绍NameNode启动过程。主要是代码级别的解释。 + +nameNode的启动主要是有NameNode.java主导的，由main函数开始了解。 + +下面是main函数里面的主要内容，可以看到主要由createNameNode实现NameNode的启动。 +```java +NameNode namenode = createNameNode(argv, null); +if (namenode != null) { + namenode.join(); +} +``` + +在createNameNode函数里面主要是分为两部分： +- 参数解析：主要关心解析startOpt，startOpt可以控制具体操作，比如format、rockback等。主要操作如下,后续会详细介绍。 + ```java + FORMAT ("-format"), + CLUSTERID ("-clusterid"), + GENCLUSTERID ("-genclusterid"), + REGULAR ("-regular"), + BACKUP ("-backup"), + CHECKPOINT("-checkpoint"), + UPGRADE ("-upgrade"), + ROLLBACK("-rollback"), + ROLLINGUPGRADE("-rollingUpgrade"), + IMPORT ("-importCheckpoint"), + BOOTSTRAPSTANDBY("-bootstrapStandby"), + INITIALIZESHAREDEDITS("-initializeSharedEdits"), + RECOVER ("-recover"), + FORCE("-force"), + NONINTERACTIVE("-nonInteractive"), + SKIPSHAREDEDITSCHECK("-skipSharedEditsCheck"), + RENAMERESERVED("-renameReserved"), + METADATAVERSION("-metadataVersion"), + UPGRADEONLY("-upgradeOnly"), + HOTSWAP("-hotswap"), + OBSERVER("-observer"); + ``` + 模型情况下会走到启动的启动的流程里面。 +- 启动NameNode或者其他操作，比如format等。 + +## 启动 + +NameNode的核心主要在NameNode的构造函数里面。 + +```java +this.haEnabled = HAUtil.isHAEnabled(conf, nsId); +// 检查HA的状态，主要是判断当前启动的是主实例还是备实例 +state = createHAState(getStartupOption(conf)); +this.allowStaleStandbyReads = HAUtil.shouldAllowStandbyReads(conf); +this.haContext = createHAContext(); +try { + initializeGenericKeys(conf, nsId, namenodeId); + // 启动NameNode + initialize(getConf()); + state.prepareToEnterState(haContext); + try { + haContext.writeLock(); + state.enterState(haContext); + } finally { + haContext.writeUnlock(); + } +} catch (IOException e) { + this.stopAtException(e); + throw e; +} catch (HadoopIllegalArgumentException e) { + this.stopAtException(e); + throw e; +} +``` + +initialize函数详解如下： + +```java +protected void initialize(Configuration conf) throws IOException { + // .... 省略 + //登录kerberos + UserGroupInformation.setConfiguration(conf); + loginAsNameNodeUser(conf); + + // 初始化监控信息 + NameNode.initMetrics(conf, this.getRole()); + StartupProgressMetrics.register(startupProgress); + + pauseMonitor = new JvmPauseMonitor(); + pauseMonitor.init(conf); + pauseMonitor.start(); + metrics.getJvmMetrics().setPauseMonitor(pauseMonitor); + + // .... 省略 + + if (NamenodeRole.NAMENODE == role) { + startHttpServer(conf); + } + // 从本地加载FSImage，并且与Editlog合并产生新的FSImage + loadNamesystem(conf); + //TODO 待确认用途 + startAliasMapServerIfNecessary(conf); + + //创建rpcserver，封装了NameNodeRpcServer、ClientRPCServer + //支持ClientNameNodeProtocol、DataNodeProtocolPB等协议 + rpcServer = createRpcServer(conf); + + initReconfigurableBackoffKey(); + + // .... 省略 + + if (NamenodeRole.NAMENODE == role) { + httpServer.setNameNodeAddress(getNameNodeAddress()); + httpServer.setFSImage(getFSImage()); + if (levelDBAliasMapServer != null) { + httpServer.setAliasMap(levelDBAliasMapServer.getAliasMap()); + } + } + + //启动执行多个重要的工作线程 + startCommonServices(conf); + startMetricsLogger(conf); +} +``` + +### startCommonServices函数详解 + +启动NameNode关键服务 + +```java +private void startCommonServices(Configuration conf) throws IOException { + // 创建NameNodeResourceChecker、激活BlockManager等 + namesystem.startCommonServices(conf, haContext); + registerNNSMXBean(); + if (NamenodeRole.NAMENODE != role) { + startHttpServer(conf); + httpServer.setNameNodeAddress(getNameNodeAddress()); + httpServer.setFSImage(getFSImage()); + if (levelDBAliasMapServer != null) { + httpServer.setAliasMap(levelDBAliasMapServer.getAliasMap()); + } + } + // 启动rpc服务 + rpcServer.start(); + try { + // 获取启动插件列表 + plugins = conf.getInstances(DFS_NAMENODE_PLUGINS_KEY, + ServicePlugin.class); + } catch (RuntimeException e) { + String pluginsValue = conf.get(DFS_NAMENODE_PLUGINS_KEY); + LOG.error("Unable to load NameNode plugins. Specified list of plugins: " + + pluginsValue, e); + throw e; + } + // 启动所有插件 + for (ServicePlugin p: plugins) { + try { + // 调用插件的start接口，需要插件自己实现，需要实现接口ServicePlugin + p.start(this); + } catch (Throwable t) { + LOG.warn("ServicePlugin " + p + " could not be started", t); + } + } + LOG.info(getRole() + " RPC up at: " + getNameNodeAddress()); + if (rpcServer.getServiceRpcAddress() != null) { + LOG.info(getRole() + " service RPC up at: " + + rpcServer.getServiceRpcAddress()); + } +} +``` + +### namesystem.startCommonServices + +在当前函数中启动blockManager和NameNodeResourceChecker，blockManager比较关键。 + +```java +void startCommonServices(Configuration conf, HAContext haContext) throws IOException { + this.registerMBean(); // register the MBean for the FSNamesystemState + writeLock(); + this.haContext = haContext; + try { + //创建NameNodeResourceChecker，并立即检查一次 + nnResourceChecker = new NameNodeResourceChecker(conf); + checkAvailableResources(); + assert !blockManager.isPopulatingReplQueues(); + StartupProgress prog = NameNode.getStartupProgress(); + prog.beginPhase(Phase.SAFEMODE); + //获取已完成的数据块总量 + long completeBlocksTotal = getCompleteBlocksTotal(); + prog.setTotal(Phase.SAFEMODE, STEP_AWAITING_REPORTED_BLOCKS, + completeBlocksTotal); + // 激活blockManager，blockManager负责管理文件系统中文件的物理块与实际存储位置的映射关系， + // 是NameNode的核心功能之一。 + blockManager.activate(conf, completeBlocksTotal); + } finally { + writeUnlock("startCommonServices"); + } + + registerMXBean(); + DefaultMetricsSystem.instance().register(this); + if (inodeAttributeProvider != null) { + inodeAttributeProvider.start(); + dir.setINodeAttributeProvider(inodeAttributeProvider); + } + // 注册快照管理器 + snapshotManager.registerMXBean(); + InetSocketAddress serviceAddress = NameNode.getServiceAddress(conf, true); + this.nameNodeHostName = (serviceAddress != null) ? serviceAddress.getHostName() : ""; +} +``` + +### blockManager.activate + +启动blockManager.activate 主要是初始化blockManager。 + +主要包含下面几个方面: +- pendingReconstruction +- datanodeManager +- bmSafeMode + +```java +public void activate(Configuration conf, long blockTotal) { + pendingReconstruction.start(); + // 初始化datanodeManager + datanodeManager.activate(conf); + this.redundancyThread.setName("RedundancyMonitor"); + this.redundancyThread.start(); + this.markedDeleteBlockScrubberThread.setName("MarkedDeleteBlockScrubberThread"); + this.markedDeleteBlockScrubberThread.start(); + this.blockReportThread.start(); + mxBeanName = MBeans.register("NameNode", "BlockStats", this); + bmSafeMode.activate(blockTotal); +} +``` + +