【Zookeeper】源码分析之服务器(三)之LeaderZooKeeperServer


一、前言

  前面分析了ZooKeeperServer源码,由于QuorumZooKeeperServer的源码相对简单,于是直接分析LeaderZooKeeperServer。

二、LeaderZooKeeperServer源码分析

  2.1 类的继承关系 

public class LeaderZooKeeperServer extends QuorumZooKeeperServer {}

  说明:LeaderZooKeeperServer继承QuorumZooKeeperServer抽象类,其会继承ZooKeeperServer中的很多方法。

  2.2 类的属性  

public class LeaderZooKeeperServer extends QuorumZooKeeperServer {
    // 提交请求处理器
    CommitProcessor commitProcessor;
}

  说明:其只有一个CommitProcessor类,表示提交请求处理器,其在处理链中的位置位于ProposalRequestProcessor之后,ToBeAppliedRequestProcessor之前。

  2.3 类的构造函数

    LeaderZooKeeperServer(FileTxnSnapLog logFactory, QuorumPeer self,
            DataTreeBuilder treeBuilder, ZKDatabase zkDb) throws IOException {
        super(logFactory, self.tickTime, self.minSessionTimeout,
                self.maxSessionTimeout, treeBuilder, zkDb, self);
    }

  说明:其直接调用父类QuorumZooKeeperServer的构造函数,然后再调用ZooKeeperServer的构造函数,逐级构造。

  2.4 核心函数分析

  1. setupRequestProcessors函数  

    protected void setupRequestProcessors() {
        // 创建FinalRequestProcessor
        RequestProcessor finalProcessor = new FinalRequestProcessor(this);
        // 创建ToBeAppliedRequestProcessor
        RequestProcessor toBeAppliedProcessor = new Leader.ToBeAppliedRequestProcessor(
                finalProcessor, getLeader().toBeApplied);
        // 创建CommitProcessor
        commitProcessor = new CommitProcessor(toBeAppliedProcessor,
                Long.toString(getServerId()), false);
        // 启动CommitProcessor
        commitProcessor.start();
        // 创建ProposalRequestProcessor
        ProposalRequestProcessor proposalProcessor = new ProposalRequestProcessor(this,
                commitProcessor);
        // 初始化ProposalProcessor
        proposalProcessor.initialize();
        // firstProcessor为PrepRequestProcessor
        firstProcessor = new PrepRequestProcessor(this, proposalProcessor);
        // 启动PrepRequestProcessor
        ((PrepRequestProcessor)firstProcessor).start();
    }

  说明:该函数表示创建处理链,可以看到其处理链的顺序为PrepRequestProcessor -> ProposalRequestProcessor -> CommitProcessor -> Leader.ToBeAppliedRequestProcessor -> FinalRequestProcessor。

  2. registerJMX函数 

    protected void registerJMX() {
        // register with JMX
        try {
            // 创建DataTreeBean
            jmxDataTreeBean = new DataTreeBean(getZKDatabase().getDataTree());
            // 进行注册
            MBeanRegistry.getInstance().register(jmxDataTreeBean, jmxServerBean);
        } catch (Exception e) {
            LOG.warn("Failed to register with JMX", e);
            jmxDataTreeBean = null;
        }
    }

  说明:该函数用于注册JMX服务,首先使用DataTree初始化DataTreeBean,然后使用DataTreeBean和ServerBean调用register函数进行注册,其源码如下 

    public void register(ZKMBeanInfo bean, ZKMBeanInfo parent)
        throws JMException
    {
        // 确保bean不为空
        assert bean != null;
        String path = null;
        if (parent != null) { // parent(ServerBean)不为空
            // 通过parent从bean2Path中获取path
            path = mapBean2Path.get(parent);
            // 确保path不为空
            assert path != null;
        }
        // 补充为完整的路径
        path = makeFullPath(path, parent);
        if(bean.isHidden())
            return;
        // 使用路径来创建名字
        ObjectName oname = makeObjectName(path, bean);
        try {
            // 注册Server
            mBeanServer.registerMBean(bean, oname);
            // 将bean和对应path放入mapBean2Path
            mapBean2Path.put(bean, path);
            // 将name和bean放入mapName2Bean
            mapName2Bean.put(bean.getName(), bean);
        } catch (JMException e) {
            LOG.warn("Failed to register MBean " + bean.getName());
            throw e;
      

  说明:可以看到会通过parent来获取路径,然后创建名字,然后注册bean,之后将相应字段放入mBeanServer和mapBean2Path中,即完成注册过程。

  3. unregisterJMX函数  

    protected void unregisterJMX() {
        // unregister from JMX
        try {
            if (jmxDataTreeBean != null) {
                // 取消注册
                MBeanRegistry.getInstance().unregister(jmxDataTreeBean);
            }
        } catch (Exception e) {
            LOG.warn("Failed to unregister with JMX", e);
        }
        jmxDataTreeBean = null;
    }

  说明:该函数用于取消注册JMX服务,其会调用unregister函数,其源码如下 

    public void unregister(ZKMBeanInfo bean) {
        if(bean==null)
            return;
        // 获取对应路径
        String path=mapBean2Path.get(bean);
        try {
            // 取消注册
            unregister(path,bean);
        } catch (JMException e) {
            LOG.warn("Error during unregister", e);
        }
        // 从mapBean2Path和mapName2Bean中移除bean
        mapBean2Path.remove(bean);
        mapName2Bean.remove(bean.getName());
    }

  说明:unregister与register的过程恰好相反,是移除bean的过程。

三、总结

  本篇学习了LeaderZooKeeperServer的源码,其源码非常简单,主要涉及到注册和取消注册服务,其大部分逻辑可以直接使用ZooKeeperServer中的方法,也谢谢各位园友的观看~