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
1
2
3
4
5
6
7
| <!-- 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
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
| 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
