Zk学习笔记——连接Zookeeper

参考：从Paxos到Zookeeper分布式一致性原理和实践

使用的zk依赖是cdh5.16.2的3.4.5

        <!-- zookeeper -->
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.5-cdh5.16.2</version>
        </dependency>

代码，其中CountDownLatch计数器参考：Java多线程——其他工具类CyclicBarrier、CountDownLatch和Exchange

初始化的计数器为1，当zk client连接到zk集群后，zk集群返回的状态为connected，计数器-1，触发InterruptedException

package com.bigdata.zookeeper;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

import java.util.concurrent.CountDownLatch;

public class ZkExample implements Watcher {

    public static CountDownLatch connectedSemaphore = new CountDownLatch(1);

    public static void main(String[] args) throws Exception {
        ZooKeeper zk = new ZooKeeper("master:2181", 5000, new ZkExample());
        System.out.println(zk.getState());
        try {
            connectedSemaphore.await();
        } catch (InterruptedException e) {
            System.out.println("Zk session established");
        }
    }

    @Override
    public void process(WatchedEvent watchedEvent) {
        System.out.println(watchedEvent);
        if (Event.KeeperState.SyncConnected == watchedEvent.getState()) {
            connectedSemaphore.countDown();
        }
    }
}

输出