hdfs/nameNode启动过程.md

@@ -1,5 +1,5 @@
 
-## 简介
+# 简介
 
 本章详细介绍NameNode启动过程。主要是代码级别的解释。
 
@@ -41,7 +41,7 @@ if (namenode != null) {
   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
+## 启动
 
 NameNode的核心主要在NameNode的构造函数里面。
 
@@ -120,3 +120,116 @@ protected void initialize(Configuration conf) throws IOException {
   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 {
+      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();
+  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);
+}
+```
+
+
+
+