Zookeeper实战案例（1）

前置知识：

Zookeeper学习笔记（1）—— 基础知识-CSDN博客

Zookeeper学习笔记（2）—— Zookeeper API简单操作-CSDN博客

Zookeeper 服务器动态上下线监听案例

需求分析

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

具体实现

首先创建节点servers：create /servers "servers"

服务器向zookeeper注册的代码

package com.why.zkCase;

import org.apache.zookeeper.*;
import org.junit.Before;

import java.io.IOException;

//服务端向zookeeper注册
public class DistributeServer {
    private static String connetString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; //客户端连接ip
    private static int sessionTimeout = 2000; //超时时间
    private ZooKeeper zkClient = null; //客户端对象
    private String parentNode = "/servers"; //父节点路径

    @Before
    public void getConnect() throws IOException {
        zkClient = new ZooKeeper(connetString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                //收到事件通知后的回调函数
                System.out.println("事件类型:" + watchedEvent.getType());
                System.out.println("事件路径:" + watchedEvent.getPath());
            }
        });
    }

    //注册服务器
    public void registServer(String hostname) throws InterruptedException, KeeperException {
        String create = zkClient.create(parentNode + "/server", hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println(hostname + "is online" + create);
    }

    //业务逻辑
    public void business(String hostname) throws Exception {
        System.out.println(hostname + " is working ...");
        Thread.sleep(Long.MAX_VALUE);
    }

    public static void main(String[] args) throws Exception {
        // 1 获取 zk 连接
        DistributeServer server = new DistributeServer();
        server.getConnect();
        // 2 利用 zk 连接注册服务器信息
        server.registServer(args[0]);
        // 3 启动业务功能
        server.business(args[0]);
    }
}

客户端代码

package com.why.zkCase;

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

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

//客户端
public class DistributeClient {
    private static String connetString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; //客户端连接ip
    private static int sessionTimeout = 2000; //超时时间
    private ZooKeeper zkClient = null; //客户端对象
    private String parentNode = "/servers"; //父节点路径

    //创建到zk的客户端连接
    @Before
    public void getConnect() throws IOException {
        zkClient = new ZooKeeper(connetString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                //收到事件通知后的回调函数
                System.out.println("事件类型:" + watchedEvent.getType());
                System.out.println("事件路径:" + watchedEvent.getPath());
                // 再次启动监听
                try {
                    getServerList();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    //获取服务器列表信息
    public void getServerList() throws InterruptedException, KeeperException {
        //获取服务器子节点信息，并对父节点进行监听
        List<String> children = zkClient.getChildren(parentNode, true);

        //存储服务器信息列表
        ArrayList<String> servers = new ArrayList<>();

        //遍历所有节点，获取主机名称信息
        for (String child : children)
        {
            byte[] data = zkClient.getData(parentNode + "/" + child, false, null);
            servers.add(new String(data));
        }

        //打印服务器列表信息
        System.out.println(servers);
    }

    // 业务功能
    public void business() throws Exception{
        System.out.println("client is working ...");
        Thread.sleep(Long.MAX_VALUE);
    }

    public static void main(String[] args) throws Exception {
        // 1 获取 zk 连接
        DistributeClient client = new DistributeClient();

        client.getConnect();
        // 2 获取 servers 的子节点信息，从中获取服务器信息列表
        client.getServerList();
        // 3 业务进程启动
        client.business();
    }
}