使用Zookeeper实现分布式锁

Zookeeper实现分布式锁原理

使用zookeeper创建临时序列节点来实现分布式锁，适用于顺序执行的程序，大体思路就是创建临时序列节点，找出最小的序列节点，获取分布式锁，程序执行完成之后此序列节点消失，通过watch来监控节点的变化，从剩下的节点的找到最小的序列节点，获取分布式锁，执行相应处理，依次类推……

Maven依赖

    <dependencies>
        <dependency>
            <groupId>com.101tec</groupId>
            <artifactId>zkclient</artifactId>
            <version>0.10</version>
        </dependency>
    </dependencies>

创建Lock接口

public interface Lock {
    //获取到锁的资源
    public void getLock();
    // 释放锁
    public void unLock();
}

创建ZookeeperAbstractLock抽象类

//将重复代码写入子类中..
public abstract class ZookeeperAbstractLock implements Lock {
    // zk连接地址
    private static final String CONNECTSTRING = "127.0.0.1:2181";
    // 创建zk连接
    protected ZkClient zkClient = new ZkClient(CONNECTSTRING);
    protected static final String PATH = "/lock";

    public void getLock() {
        if (tryLock()) {
            System.out.println("##获取lock锁的资源####");
        } else {
            // 等待
            waitLock();
            // 重新获取锁资源
            getLock();
        }

    }

    // 获取锁资源
    abstract boolean tryLock();

    // 等待
    abstract void waitLock();

    public void unLock() {
        if (zkClient != null) {
            zkClient.close();
            System.out.println("释放锁资源...");
        }
    }

}

ZookeeperDistrbuteLock类

public class ZookeeperDistrbuteLock extends ZookeeperAbstractLock {
    private CountDownLatch countDownLatch = null;

    @Override
    boolean tryLock() {
        try {
            zkClient.createEphemeral(PATH);
            return true;
        } catch (Exception e) {
//            e.printStackTrace();
            return false;
        }

    }

    @Override
    void waitLock() {
        IZkDataListener izkDataListener = new IZkDataListener() {

            public void handleDataDeleted(String path) throws Exception {
                // 唤醒被等待的线程
                if (countDownLatch != null) {
                    countDownLatch.countDown();
                }
            }
            public void handleDataChange(String path, Object data) throws Exception {

            }
        };
        // 注册事件
        zkClient.subscribeDataChanges(PATH, izkDataListener);
        if (zkClient.exists(PATH)) {
            countDownLatch = new CountDownLatch(1);
            try {
                countDownLatch.await();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        // 删除监听
        zkClient.unsubscribeDataChanges(PATH, izkDataListener);
    }

}

使用Zookeeper锁运行效果

public class OrderService implements Runnable {
    private OrderNumGenerator orderNumGenerator = new OrderNumGenerator();
    // 使用lock锁
    // private java.util.concurrent.locks.Lock lock = new ReentrantLock();
    private Lock lock = new ZookeeperDistrbuteLock();
    public void run() {
        getNumber();
    }
    public void getNumber() {
        try {
            lock.getLock();
            String number = orderNumGenerator.getNumber();
            System.out.println(Thread.currentThread().getName() + ",生成订单ID:" + number);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unLock();
        }
    }
    public static void main(String[] args) {
        System.out.println("####生成唯一订单号###");
//        OrderService orderService = new OrderService();
        for (int i = 0; i < 100; i++) {
            new Thread( new OrderService()).start();
        }
    }
}