6、zookeeper应用场景-分布式唯一ID

分布式唯一id案例

　　原理：使用zookeeper有序节点，节点后会加上有序的id，用这个id来当唯一ID

　　在过去的单库单表型系统中，通常第可以使用数据库字段自带的auto_ increment属性来自动为每条记录生成个唯一的ID。

但是分库分表后，就无法在依靠数据库的auto_ increment属性来唯一标识一条记录了。此时我们就可以用zookeeper在分布式环境下生成全局唯一ID

案例：

public class IdGenerate {

    private static final String IP = "192.168.133.133:2181";
    private static CountDownLatch countDownLatch = new CountDownLatch(1);
    private static ZooKeeper zooKeeper;

    public static String generateId() throws Exception {
        return zooKeeper.create("/id", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
    }

    public static void main(String[] args) throws Exception {
        zooKeeper = new ZooKeeper(IP, 5000, new ZKWatcher());
        countDownLatch.await();
        ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(5, 5, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(10));
        for (int i = 0; i < 10; i++) {
            threadPoolExecutor.execute(() -> {
                try {
                    System.out.println(generateId());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        }
        TimeUnit.SECONDS.sleep(50);
        threadPoolExecutor.shutdown();
    }

    static class ZKWatcher implements Watcher {
        @Override
        public void process(WatchedEvent watchedEvent) {
            countDownLatch.countDown();
            System.out.println("zk的监听器" + watchedEvent.getType());
        }
    }
}