Zookeeper分布式入门——ZK分布式锁的简单实现

Zookeeper分布式入门——ZK分布式锁的简单实现
使用InterProcessMutex实现

InterProcessMutex基于Zookeeper实现了分布式的公平可重入互斥锁，类似于单个JVM进程内的ReentrantLock

1.初始化InterProcessMutex

private static InterProcessMutex mutex = new InterProcessMutex(client, "/curator/lock");

2.获取锁

    //获得了锁
    public static boolean acquire(long time, TimeUnit unit){
        try {
            return mutex.acquire(time,unit);
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

3.释放锁

    //释放锁
    public static void release(){
        try {
            mutex.release();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

测试：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.ExponentialBackoffRetry;
/**
 * 基于curator的zookeeper分布式锁
 * 这里我们开启5个线程，每个线程获取锁的最大等待时间为5秒，为了模拟具体业务场景，方法中设置4秒等待时间。
 * 
 */
public class CuratorUtil {
    private static String address = "192.168.12.101:2181";
    
    public static void main(String[] args) {
        //1、重试策略：初试时间为1s 重试3次
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3); 
        //2、通过工厂创建连接
        CuratorFramework client = CuratorFrameworkFactory.newClient(address, retryPolicy);
        //3、开启连接
        client.start();
        //4 分布式锁
        final InterProcessMutex mutex = new InterProcessMutex(client, "/curator/lock"); 
        //读写锁
        //InterProcessReadWriteLock readWriteLock = new InterProcessReadWriteLock(client, "/readwriter");
        
        ExecutorService fixedThreadPool = Executors.newFixedThreadPool(5);
        
        for (int i = 0; i < 5; i++) {
            fixedThreadPool.submit(new Runnable() {
                @Override
                public void run() {
                    boolean flag = false;
                    try {
                        //尝试获取锁，最多等待5秒
                        flag = mutex.acquire(5, TimeUnit.SECONDS);
                        Thread currentThread = Thread.currentThread();
                        if(flag){
                            System.out.println("线程"+currentThread.getId()+"获取锁成功");
                        }else{
                            System.out.println("线程"+currentThread.getId()+"获取锁失败");
                        }
                        //模拟业务逻辑，延时4秒
                        Thread.sleep(4000);
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally{
                        if(flag){
                            try {
                                mutex.release();
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            });
        }
    }
}

这里我们开启5个线程，每个线程获取锁的最大等待时间为5秒，为了模拟具体业务场景，方法中设置4秒等待时间。开始执行main方法，通过ZooInspector监控/curator/lock下的节点如下图：

对，没错，设置4秒的业务处理时长就是为了观察生成了几个顺序节点。果然如案例中所述，每个线程都会生成一个节点并且还是有序的。观察控制台，我们会发现只有两个线程获取锁成功，另外三个线程超时获取锁失败会自动删除节点。线程执行完毕我们刷新一下/curator/lock节点，发现刚才创建的五个子节点已经不存在了。