zookeeper源码分析之事务请求处理

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已于 2024-09-04 09:04:52 修改

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分类专栏： Java后台及存储文章标签：开发语言 java 源码分析

于 2024-08-19 15:42:15 首次发布

本文链接：https://blog.youkuaiyun.com/feivirus/article/details/141327104

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一.参考

zookeeper启动和选举的源码分析参考之前的帖子.

二.源码

1.职责链模式.

每次经过的processor都是异步处理，加入当前processor的队列，然后新的线程从队列里面取出数据处理.

PrepRequestProcessor 检查ACL权限,创建ChangeRecord.

SyncRequestProcessor 负责事务日志的持久化，写入snapshot和log文件.

FinalRequestProcessor 提交leader事务.向observer发送请求,提交事务.

1.1如果是leader启动的时候会倒序初始化下面6个processor,

LeaderRequestProcessor->PrepRequestProcessor->ProposalRequestProcessor(含有SyncRequestProcessor的成员变量,processRequest中先调用下一个，再调用SyncRequestProcessor)->CommitProcessor->ToBeAppliedRequestProcessor->FinalRequestProcessor.

 protected void setupRequestProcessors() {
        RequestProcessor finalProcessor = new FinalRequestProcessor(this);
        RequestProcessor toBeAppliedProcessor = new Leader.ToBeAppliedRequestProcessor(finalProcessor, getLeader());
        commitProcessor = new CommitProcessor(toBeAppliedProcessor, Long.toString(getServerId()), false, getZooKeeperServerListener());
        commitProcessor.start();
        ProposalRequestProcessor proposalProcessor = new ProposalRequestProcessor(this, commitProcessor);
        proposalProcessor.initialize();
        prepRequestProcessor = new PrepRequestProcessor(this, proposalProcessor);
        prepRequestProcessor.start();
        firstProcessor = new LeaderRequestProcessor(this, prepRequestProcessor);

        setupContainerManager();
}

1.2.如果是follower启动，会进入ZooKeeperServer#startupWithServerState倒序初始化下面三个processor,

FollowerRequestProcessor->CommitProcessor->FinalRequestProcessor.

另外两个，是在Follower的主循环中,接收到PROPOSAL请求时，会依次调用SyncRequestProcessor->SendAckRequestProcessor,在下面二.2中有详细分析.

  protected void setupRequestProcessors() {
        RequestProcessor finalProcessor = new FinalRequestProcessor(this);
        commitProcessor = new CommitProcessor(finalProcessor, Long.toString(getServerId()), true, getZooKeeperServerListener());
        commitProcessor.start();
        firstProcessor = new FollowerRequestProcessor(this, commitProcessor);
        ((FollowerRequestProcessor) firstProcessor).start();
        syncProcessor = new SyncRequestProcessor(this, new SendAckRequestProcessor(getFollower()));
        syncProcessor.start();
    }