Zookeeper-day04-服务器动态上下线监听案例

1：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。

2：需求分析

 3：案例实操

        1：先在集群上创建/servers 节点

        2： 服务器与zookeeper关联起来，创建节点联系

package com.atguigu.case1;

import org.apache.zookeeper.*;

import java.io.IOException;

public class DistributeServer {

    private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout = 2000;
    private ZooKeeper zk;

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        
        DistributeServer server = new DistributeServer();
        //1.获取zk连接
        server.getConnect();

        //2.注册服务器到zk集群
        server.regist(args[0]);

        //3.启动业务逻辑（睡觉）
        server.business();
    }

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

    private void regist(String hostname) throws KeeperException, InterruptedException {
        String create = zk.create("/servers/"+hostname, hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);

        System.out.println(hostname + "is online");

    }

    private void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            public void process(WatchedEvent watchedEvent) {

            }
        });

    }

}

        3：客户端创建监听程序

package com.atguigu.case1;

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

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

public class DistributeClient {

    private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout = 2000;
    private ZooKeeper zk;

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        DistributeClient client = new DistributeClient();
        //1.获取zk连接
        client.getConnect();
        //2.监听/servers下面子节点的增加和删除
        client.getServerList();

        //3.业务逻辑（睡觉）
        client.business();
    }

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

    private void getServerList() throws KeeperException, InterruptedException {
        List children = zk.getChildren("/servers", true);

        ArrayList servers = new ArrayList();
        for (String child : children) {
            byte[] data = zk.getData("/servers/" + child, false, null);

            servers.add(new String(data));
        }

        //打印
        System.out.println(servers);
    }

    private void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                try {
                    getServerList();
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }

}

        4：命令行上测试