Zookeeper监听服务器节点动态上下线案例

​需求：​

某分布式系统中，主节点可以有多台，可以动态上下线，任意一台客户端都能实时感知到主节点服务器的上下线

服务端代码

package com.zyd.zook;

import java.io.IOException;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.ZooDefs.Ids;

public class ZkServer {

    private String connectString = "testnote01:2181,testnote02:2181,testnote03:2181";
    private int sessionTimeout = 2000;  
    private ZooKeeper zkClient;
    private String parentNode = "/servers";

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
      ZkServer server = new ZkServer();
      //1 获取连接zkServer
      server.getConnect();
      //2 注册服务器节点信息
      server.regist(args[0]);
      //3 业务逻辑处理
      server.business(args[0]);
    }

    private void business(String hostname) {
      System.out.println(hostname+"is online");
    }

    private void regist(String hostname) throws KeeperException, InterruptedException {
      String path = zkClient.create(parentNode+"/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);

      System.out.println(path);
    }

    private void getConnect() throws IOException {
      zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher(){

        @Override
        public void process(WatchedEvent event) {

        }

      });
    }
}

客户端代码

package com.zyd.zook;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

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

public class ZkClient {
  public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
    ZkClient client = new ZkClient();
    //1 获取连接
    client.getConnect();
    //2 监听服务器节点路径
    client.getServerList();
    //3 业务处理
    client.business();
  }

  private void business() throws InterruptedException {
    Thread.sleep(Long.MAX_VALUE);
  }

  //获取服务器列表
  private void getServerList() throws KeeperException, InterruptedException {
    // 获取服务器子节点信息，并且对父节点进行监听
        List<String> children = zkClient.getChildren(parentNode, true);
    //存储服务器列表
    ArrayList<String> serverList = new ArrayList<String>();
    //获取每个节点中的数据
    for (String child : children) {
    byte[] data = zkClient.getData("/servers"+child, false, null);
    }
    System.out.println(serverList);
  }

  private String connectString = "testnote01:2181,testnote02:2181,testnote03:2181";
  private int sessionTimeout = 2000;  
  ZooKeeper zkClient ;
  private String parentNode = "/servers";

  private void getConnect() throws IOException {
    zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher(){

      @Override
      public void process(WatchedEvent event) {
        try {
           getServerList();
        } catch (KeeperException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        } catch (InterruptedException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }

      }});
  }
}

客户端代码有问题,bug不知

Exception in thread "main" org.apache.zookeeper.KeeperException$NoNodeException: KeeperErrorCode = NoNode for /serversserver0000000000
  at org.apache.zookeeper.KeeperException.create(KeeperException.java:111)
  at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
  at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1212)
  at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1241)
  at com.zyd.zook.ZkClient.getServerList(ZkClient.java:35)
  at com.zyd.zook.ZkClient.access$0(ZkClient.java:28)
  at com.zyd.zook.ZkClient$1.process(ZkClient.java:51)