4.1 Java API操作

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.util.List;
public class TestZookeepr {
    private String connect = "192.168.209.131:2181";
    private int timeOut = 2000;
    private ZooKeeper zkClient;
    @Before
    public void init() throws IOException {
        zkClient = new ZooKeeper(connect, timeOut, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
            }
        });
    }
    //创建结点
    @Test
    public void createNode () throws KeeperException, InterruptedException {
        String path = zkClient.create("/zbc","hellozbc".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        System.out.println(path);
    }
    //获取子结点，并监控数据的变化
    @Test
    public void getDataAndWatch() throws KeeperException, InterruptedException {
        List<String> nodes = zkClient.getChildren("/",true);
        nodes.forEach(System.out::println);
    }
    //判断节点是否存在
    @Test
    public void exist() throws KeeperException, InterruptedException {
        Stat stat = zkClient.exists("/zbc",false);
        System.out.println(stat == null ? "not exits":"exist");
    }
}

4.2 动态获取节点

import org.apache.zookeeper.*;
import java.io.IOException;
public class DistributeServer {
    private ZooKeeper zkServer = null;
    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        DistributeServer distributeServer = new DistributeServer();
        //1. 链接zookeeper集群
        distributeServer.getConnect();
        //2. 注册节点
        distributeServer.regist(args[0]);
        //3.业务逻辑处理
        distributeServer.business();
    }
    private void business() throws InterruptedException {
        Thread.sleep(Long.MAX_VALUE);
    }
    private void regist(String hostNmae) throws KeeperException, InterruptedException {
        zkServer.create("/servers/server",hostNmae.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
    }
    private void getConnect() throws IOException {
//        String connectString = "ip:port,ip:port";
        String connectString = "";
        int timeout = 2000;
        new ZooKeeper(connectString, timeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
            }
        });
    }
}

import org.apache.zookeeper.*;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class DistributeClient {
    private ZooKeeper zkServer = null;
    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        DistributeClient distributeClient = new DistributeClient();
        //1. 链接集群
        distributeClient.getConnect();
        //2. 注册监听
        distributeClient.getChildren();
        //3. 业务处理
        distributeClient.business();
    }
    private void getChildren() throws KeeperException, InterruptedException {
        List<String> childres = zkServer.getChildren("/servers",true);
        // 储存服务器节点主机名称
        List<String> hots = new ArrayList<String>();
        for (String children:childres) {
           byte[] data = zkServer.getData("/servers/"+children,false,null);
           hots.add(new String(data));
        }
        // 将所有主机名称打印到控制台
        System.out.println(hots);
    }
    private void business() throws InterruptedException {
        Thread.sleep(Long.MAX_VALUE);
    }
    private void getConnect() throws IOException {
//        String connectString = "ip:port,ip:port";
        String connectString = "";
        int timeout = 2000;
        new ZooKeeper(connectString, timeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                try {
                    getChildren();
                } catch (KeeperException | InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

4.3 企业面试真题

4.3.1 请简述Zookeeper的选举机制
半数机制
4.3.2 Zookeeper监听原理是什么
4.3.3 Zookeeper部分方式有几种？集群中的角色有哪些，集群最少需要几天机器

1. 部署方式有单机部署和集群部署
2. 角色：Leader和Follower

3. 集群最少需要3太机器

   4.3.4 Zookeeper 的常用命令