java - 有zookeeper相关的大神么？使用ZKClient创建节点，但是服务器中并没有显示？

问题描述

我按照zk权威指南上的代码创建节点：

package com.zkstudy;import java.io.IOException;import java.util.Random;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.KeeperException;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.ZooDefs.Ids;import org.apache.zookeeper.ZooKeeper;import org.apache.zookeeper.data.Stat;public class Master implements Watcher { private ZooKeeper zk = null; private String host; private String serverId = null; private boolean isLeader = false; public Master(String host) {this.host = host;Random radom = new Random();serverId = Integer.toHexString(radom.nextInt()); } public void start() {try { this.zk = new ZooKeeper(host, 15000, this);} catch (IOException e) { e.printStackTrace();} } public void createMaster() {while (true) { try {zk.create('/master', serverId.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);isLeader = true;break; } catch (KeeperException e) {e.printStackTrace();isLeader = false;break; } catch (InterruptedException e) {e.printStackTrace(); } if (checkMaster()) {break; }} } public boolean checkMaster() {while (true) { Stat stat = new Stat(); try {byte[] data = zk.getData('/master', false, stat);isLeader = new String(data).equals(serverId);return true; } catch (KeeperException e) {e.printStackTrace();return false; } catch (InterruptedException e) {e.printStackTrace(); }} } public void process(WatchedEvent event) {System.out.println('watcher thread:---------->' + Thread.currentThread().getId());System.out.println('event:---------->' + event); } public static void main(String[] args) throws InterruptedException {Master master = new Master('123.206.28.37:2181');master.start();master.createMaster();if (master.isLeader) { System.out.println('i am master');}System.out.println('main thread:---------->' + Thread.currentThread().getId());Thread.sleep(5000); }}

然后我运行了两遍。出现了如下问题：

watcher thread:---------->10event:---------->WatchedEvent state:SyncConnected type:None path:nullorg.apache.zookeeper.KeeperException$NodeExistsException: KeeperErrorCode = NodeExists for /mastermain thread:---------->1 at org.apache.zookeeper.KeeperException.create(KeeperException.java:119) at org.apache.zookeeper.KeeperException.create(KeeperException.java:51) at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:783) at com.zkstudy.Master.createMaster(Master.java:40) at com.zkstudy.Master.main(Master.java:83)

提示master节点已经存在。但是我在命令行里面查看却没有发现master节点：

[zk: localhost:2181(CONNECTED) 10] ls[zk: localhost:2181(CONNECTED) 11] ls /[zk, zookeeper][zk: localhost:2181(CONNECTED) 12]

请问这是为什么呢？zk使用的是单节点，不是伪集群。

问题解答

自问自答吧。因为我创建的是临时节点，临时节点在绘画断开以后会自动删除，估计这个 ls / 命令应该是列举的持久节点。