Zookeeper学习---3、服务器动态上下线监听案例、ZooKeeper 分布式锁案例、企业面试真题

package org.example.zkcase1;
import org.apache.zookeeper.*;
import java.io.IOException;
/**
 * @ClassName DistributeServer
 * @Description TODO
 * @Author Zouhuiming
 * @Date 2023/5/25 9:12
 * @Version 1.0
 */
public class DistributeServer {
    private String connectString="hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout=2000;
    ZooKeeper zk=null;
    private String parentNode="/servers";
    //创建到zk的客户端连接
    public void getConnect() throws IOException {
        zk=new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
            }
        });
    }
    //注册服务器
    public void registServer(String hostname) throws InterruptedException, KeeperException {
        String create = zk.create(parentNode + "/servers", hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println(hostname+"is online"+create);
    }
    //业务功能
    public void business(String hostname) throws InterruptedException {
        System.out.println(hostname+" is working...");
        Thread.sleep(Long.MAX_VALUE);
    }
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        //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]);
    }
}

package org.example.zkcase1;
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;
/**
 * @ClassName DistributeClient
 * @Description TODO
 * @Author Zouhuiming
 * @Date 2023/5/25 9:23
 * @Version 1.0
 */
public class DistributeClient {
    private String connectionString="hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout=2000;
    private ZooKeeper zk;
    private String parentNode="/servers";
    //创建到zk的客户端连接
    public void getConnection() throws IOException {
        zk=new ZooKeeper(connectionString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                //再次启动监听
                try {
                    getServerList();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                } catch (KeeperException e) {
                    throw new RuntimeException(e);
                }
            }
        });
    }
    //获取服务器列表信息
    public void getServerList() throws InterruptedException, KeeperException {
        //1、获取服务器子节点信息，并且对父节点进行监听
        List<String> children = zk.getChildren(parentNode, true);
        //2、储存服务器信息列表
        ArrayList<String> servers=new ArrayList<>();
        //3、遍历所有节点，获取节点中的主机名称信息
        for (String child : children) {
            byte[] data = zk.getData(parentNode + "/" + child, false, null);
            servers.add(new String(data));
        }
        //4、打印服务器列表信息
        System.out.println(servers);
    }
    //业务功能
    public void business() throws InterruptedException {
        System.out.println("client is working...");
        Thread.sleep(Long.MAX_VALUE);
    }
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        //1、获取zk连接
        DistributeClient client=new DistributeClient();
        client.getConnection();
        //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();
    }
}

package org.example.lock;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
/**
 * @ClassName DistributedLock
 * @Description TODO
 * @Author Zouhuiming
 * @Date 2023/5/25 14:51
 * @Version 1.0
 */
public class DistributedLock {
    //Zookeeper server列表
    private String connectString="hadoop102:2181,hadoop103:2181,hadoop104:2181";
    //超时时间
    private int sessionTimeout=2000;
    private ZooKeeper zk;
    private String rootNode="locks";
    private String subNode="seq-";
    //当前client等待的子节点
    private String waitPath;
    //Zookeeper连接
    private CountDownLatch connectLatch=new CountDownLatch(1);
    //Zookeeper节点等待
    private CountDownLatch waitLatch=new CountDownLatch(1);
    //当前client创建的子节点
    private String currentNode;
    //和zk服务建立连接，并创建根节点
    public DistributedLock() throws IOException, InterruptedException, KeeperException {
        zk=new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                //连接建立时，打开latch，唤醒wait在该latch上的线程
                if (watchedEvent.getState()==Event.KeeperState.SyncConnected){
                    try {
                        connectLatch.countDown();
                    } catch (Exception e){
                        e.printStackTrace();
                    }
                }
                //发生了waitPath的删除事件
                if (watchedEvent.getType()==Event.EventType.NodeDeleted&&watchedEvent.getPath().equals(waitPath)){
                    waitLatch.countDown();
                }
            }
        });
        //等待连接建立
        connectLatch.await();
        //获取根节点状态
        Stat stat = zk.exists("/" + rootNode, false);
        if (stat==null){
            System.out.println("根节点不存在");
            zk.create("/"+rootNode,new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
        }
    }
    //加锁方法
    public void zkLock(){
        try {
            //在根节点下创建临时顺序节点，返回值为创建的节点路径
            currentNode=zk.create("/"+rootNode+"/"+subNode,null,ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
            //wait一会儿，让结果更加清晰一些
            Thread.sleep(10);
            //注意，没有必要监听"/locks"的子节点的变化情况
            List<String> childrenNodes = zk.getChildren("/" + rootNode, false);
            //列表中只有一个子节点，那肯定就是currentNode，说明client获得锁
            if (childrenNodes.size()==1){
                return;
            }
            else {
                //对根节点下的所有临时顺序节点从小到大排序
                Collections.sort(childrenNodes);
                //当前节点名称
                String thisNode = currentNode.substring(("/" + rootNode + "/").length());
                int index = childrenNodes.indexOf(thisNode);
                if (index==-1){
                    System.out.println("数据异常");
                } else if (index==0) {
                    //index==0,说明thisNode在列表中最小，当前client获得锁
                    return;
                }else {
                    //获得排名比current前一位的节点
                    this.waitPath="/"+rootNode+"/"+childrenNodes.get(index-1);
                    //在waitPath上注册监听器，当waitPath被删除时，Zookeeper会回调监听器的process方法
                    zk.getData(waitPath,true,new Stat());
                    //进入等待锁状态
                    waitLatch.await();
                    return;
                }
            }
        } catch (KeeperException e) {
            throw new RuntimeException(e);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
    //解锁方法
    public void zkUnlock(){
        try {
            zk.delete(this.currentNode,-1);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } catch (KeeperException e) {
            throw new RuntimeException(e);
        }
    }
}

package org.example.lock;
import org.apache.zookeeper.KeeperException;
import java.io.IOException;
/**
 * @ClassName DistributedLockTest
 * @Description TODO
 * @Author Zouhuiming
 * @Date 2023/5/25 15:27
 * @Version 1.0
 */
public class DistributedLockTest {
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        //创建分布式锁
        final DistributedLock lock1=new DistributedLock();
        final DistributedLock lock2=new DistributedLock();
        new Thread(new Runnable() {
            @Override
            public void run() {
                //获取锁对象
                try {
                    lock1.zkLock();
                    System.out.println("线程1获取锁");
                    Thread.sleep(5*1000);
                    lock1.zkUnlock();
                    System.out.println("线程1释放锁");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                //获取锁对象
                try {
                    lock2.zkLock();
                    System.out.println("线程2获取锁");
                    Thread.sleep(5*1000);
                    lock2.zkUnlock();
                    System.out.println("线程2释放锁");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
}

<dependency>
 <groupId>org.apache.curator</groupId>
 <artifactId>curator-framework</artifactId>
 <version>4.3.0</version>
</dependency>
<dependency>
 <groupId>org.apache.curator</groupId>
 <artifactId>curator-recipes</artifactId>
 <version>4.3.0</version>
</dependency>
<dependency>
 <groupId>org.apache.curator</groupId>
 <artifactId>curator-client</artifactId>
 <version>4.3.0</version>
</dependency>

package org.example.zkCase2;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.InterProcessLock;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.ExponentialBackoffRetry;
/**
 * @ClassName CuratorLockTest
 * @Description TODO
 * @Author Zouhuiming
 * @Date 2023/5/25 15:52
 * @Version 1.0
 */
public class CuratorLockTest {
    private String rootNode="/locks";
    //zookeeper server列表
    private String connectString="hadoop102:2181,hadoop103:2181,hadoop104:2181";
    //connection超时时间
    private  int connectionTimeOut=2000;
    //session超时时间
    private int sessionTimeOut=2000;
    public static void main(String[] args) {
        new CuratorLockTest().test();
    }
    //测试
    private  void test(){
        //创建分布式锁1
        final InterProcessLock lock1=new InterProcessMutex(getCuratorFramework(),rootNode);
        //创建分布式锁2
        final InterProcessLock lock2=new InterProcessMutex(getCuratorFramework(),rootNode);
        new Thread(new Runnable() {
            @Override
            public void run() {
                //获取锁对象
                try {
                    lock1.acquire();
                    System.out.println("线程1获取锁");
                    //测试锁重入
                    lock1.acquire();
                    System.out.println("线程1再次获取锁");
                    lock1.release();
                    System.out.println("线程1释放锁");
                    lock1.release();
                    System.out.println("线程1再次释放锁");
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                //获取锁对象
                try {
                    lock2.acquire();
                    System.out.println("线程2获取锁");
                    //测试锁重入
                    lock2.acquire();
                    System.out.println("线程2再次获取锁");
                    lock2.release();
                    System.out.println("线程2释放锁");
                    lock2.release();
                    System.out.println("线程2再次释放锁");
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            }
        }).start();
    }
    //分布式锁初始化
    private CuratorFramework getCuratorFramework() {
        //重试策略，初始时间3秒，重试3次
        ExponentialBackoffRetry policy = new ExponentialBackoffRetry(3000, 3);
        //通过工厂创建Curator
        CuratorFramework client= CuratorFrameworkFactory.builder()
                .connectString(connectString)
                .connectionTimeoutMs(connectionTimeOut)
                .sessionTimeoutMs(sessionTimeOut)
                .retryPolicy(policy)
                .build();
        //开启连接
        client.start();
        System.out.println("zookeeper 初始化完成...");
        return client;
    }
}