BPServiceActor详解

hdfs/BPServiceActor详解.md

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+
+# 简介
+BPServiceActor 主要在DataNode中用于和NameNode沟通的类。主要功能如下：
+- 与 namenode 进行预注册握手。
+- 向 namenode 注册。
+- 定期向 namenode 发送心跳。
+- 处理从 namenode 收到的命令。
+
+
+# 核心功能
+
+## 预注册
+
+
+## 注册DataNode
+
+### DataNode注册核心逻辑
+
+注册DataNode的核心函数是register
+
+```java
+void register(NamespaceInfo nsInfo) throws IOException {
+    // The handshake() phase loaded the block pool storage
+    // off disk - so update the bpRegistration object from that info
+    DatanodeRegistration newBpRegistration = bpos.createRegistration();
+
+    LOG.info(this + " beginning handshake with NN");
+
+    while (shouldRun()) {
+        try {
+            // 向NN注册DataNodde
+            newBpRegistration = bpNamenode.registerDatanode(newBpRegistration);
+            newBpRegistration.setNamespaceInfo(nsInfo);
+            bpRegistration = newBpRegistration;
+            break;
+            // ... 省略部分异常处理
+        }
+    }
+
+    if (bpRegistration == null) {
+        throw new IOException("DN shut down before block pool registered");
+    }
+
+    // .. 省略 ..
+    // reset lease id whenever registered to NN.
+    // ask for a new lease id at the next heartbeat.
+    fullBlockReportLeaseId = 0;
+
+    // random short delay - helps scatter the BR from all DatanodeRegistration 
+    // 定时汇报block块信息给NN
+    scheduler.scheduleBlockReport(dnConf.initialBlockReportDelayMs, true);
+}
+```
+
+### NameNode 处理注册信息
+
+NameNode处理DataNode的注册信息，主要接口是在NameNodeRpcServer的ipc接口registerDatanode。
+其主要的实现实在DatanodeManager中的函数registerDatanode。
+
+
+主要实现如下：
+
+```java
+// update cluster map
+getNetworkTopology().remove(nodeS);
+if(shouldCountVersion(nodeS)) {
+    decrementVersionCount(nodeS.getSoftwareVersion());
+}
+nodeS.updateRegInfo(nodeReg);
+
+nodeS.setSoftwareVersion(nodeReg.getSoftwareVersion());
+nodeS.setDisallowed(false); // Node is in the include list
+
+// resolve network location
+if(this.rejectUnresolvedTopologyDN) {
+    nodeS.setNetworkLocation(resolveNetworkLocation(nodeS));
+    nodeS.setDependentHostNames(getNetworkDependencies(nodeS));
+} else {
+    nodeS.setNetworkLocation(
+            resolveNetworkLocationWithFallBackToDefaultLocation(nodeS));
+    nodeS.setDependentHostNames(
+            getNetworkDependenciesWithDefault(nodeS));
+}
+getNetworkTopology().add(nodeS);
+resolveUpgradeDomain(nodeS);
+
+// also treat the registration message as a heartbeat
+heartbeatManager.register(nodeS);
+incrementVersionCount(nodeS.getSoftwareVersion());
+startAdminOperationIfNecessary(nodeS);
+success = true;
+
+```
+
+主要做了下面两件事：
+- 更新节点信息，比如网络拓扑信息。
+- 在心跳管理里面注册当前节点。只要将节点信息添加到节点列表里面即可。
+
+
+## 发送心跳
+
+
+## 处理NN的命令
+
+
+