ZooKeeper 构建分布式唯一ID生成器

发布时间：2022-11-12 09:30

背景

原文地址：https://duktig.cn/archives/90/

上篇文章介绍了 解决分布式ID问题的各种方案，详情可参看上篇文章：分布式ID常用方案——UUID、MySQL、Redis、ZooKeeper、雪花算法、美团Leaf……

可参看：Redis构建分布式唯一ID生成器

本篇文章着重介绍 ZooKeeper生成分布式ID

源码参看：https://github.com/duktig666/distributed-programme

ZooKeeper实现分布式ID分析

ZooKeeper分布式ID生成,原理是利用ZooKeeper的临时有序节点，生成全局唯一的ID。

多个客户端同时创建同一节点，zk保证了能有序的创建，创建成功并返回的path类似于/root/generateid0000000001酱紫的，可以看到是顺序有规律的，能较好的解决这个问题，缺点是，会依赖于zk。

实现

1. 环境搭建

1.1 引入依赖

<dependency>
    <groupId>org.apache.zookeepergroupId>
    <artifactId>zookeeperartifactId>
    <version>3.5.7version>
dependency>
<dependency>
    <groupId>org.apache.logging.log4jgroupId>
    <artifactId>log4j-coreartifactId>
    <version>2.8.2version>
dependency>

<dependency>
    <groupId>org.apache.curatorgroupId>
    <artifactId>curator-frameworkartifactId>
    <version>4.3.0version>
dependency>
<dependency>
    <groupId>org.apache.curatorgroupId>
    <artifactId>curator-recipesartifactId>
    <version>4.3.0version>
dependency>
<dependency>
    <groupId>org.apache.curatorgroupId>
    <artifactId>curator-clientartifactId>
    <version>4.3.0version>
dependency>


<dependency>
    <groupId>org.projectlombokgroupId>
    <artifactId>lombokartifactId>
dependency>

2. ZooKeeper实现分布式ID

2.1 代码实现

/**
 * description:zk实现分布式id
 *
 * @author RenShiWei
 * Date: 2021/8/20 9:20
 **/
@Slf4j
public class ZookeeperUniqueID implements Watcher {

    /** 计数器对象 */
    public static CountDownLatch countDownLatch = new CountDownLatch(1);

    /** 连接对象 */
    public static ZooKeeper zooKeeper;

    private final String IP = "127.0.0.1:2181";

    /** 用户生成序号的节点 */
    private final String DEFAULT_PATH = "/uniqueId";
    /** 根节点 */
    private final String ROOT_PATH = "/uniqueId";

    public ZookeeperUniqueID() {
        try {
            zooKeeper = new ZooKeeper(IP, 6000, this);
            //等待zk正常连接后，往下走程序
            countDownLatch.await();
            // 判断根节点是否存在
            Stat stat = zooKeeper.exists(ROOT_PATH, false);
            if (stat == null) {
                // 创建一下根节点
                zooKeeper.create(ROOT_PATH, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void process(WatchedEvent watchedEvent) {
        try {
            //EventType = None时
            if (watchedEvent.getType() == Watcher.Event.EventType.None) {
                if (watchedEvent.getState() == Watcher.Event.KeeperState.SyncConnected) {
                    log.info("连接成功");
                    countDownLatch.countDown();
                } else if (watchedEvent.getState() == Watcher.Event.KeeperState.Disconnected) {
                    log.info("断开连接");
                } else if (watchedEvent.getState() == Watcher.Event.KeeperState.Expired) {
                    log.info("会话超时");
                    // 超时后服务器端已经将连接释放，需要重新连接服务器端
                    zooKeeper = new ZooKeeper(IP, 6000, this);
                } else if (watchedEvent.getState() == Watcher.Event.KeeperState.AuthFailed) {
                    log.info("认证失败");
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 根据 zk 临时有序节点，生成唯一ID
     *
     * @return 唯一ID
     */
    public String getUniqueId() {
        String path = "";
        //创建临时有序节点
        try {
            path = zooKeeper.create(ROOT_PATH + DEFAULT_PATH, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,
                    CreateMode.EPHEMERAL_SEQUENTIAL);
            log.info("zk创建临时有序节点：{}", path);
        } catch (KeeperException | InterruptedException e) {
            e.printStackTrace();
        }
        //截取defaultPath的长度
        return path.substring(DEFAULT_PATH.length());
    }

}

2.2 测试

public class ZookeeperUniqueIDTest {

    /**
     * 测试 zk 生成唯一ID
     */
    @Test
    public void getUniqueId() {
        ZookeeperUniqueID zookeeperUniqueID = new ZookeeperUniqueID();
        for (int i = 0; i < 10; i++) {
            System.out.println("分布式唯一ID:" + zookeeperUniqueID.getUniqueId());
        }
    }

    /**
     * 测试 zk 生成唯一ID（多线程下）
     */
    @Test
    public void getUniqueIdForMore() {
        ZookeeperUniqueID zookeeperUniqueID = new ZookeeperUniqueID();

        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                System.out.println(Thread.currentThread().getName() + "分布式唯一ID:" + zookeeperUniqueID.getUniqueId());
            }
        }, "thread-0").start();

        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                System.out.println(Thread.currentThread().getName() + "分布式唯一ID:" + zookeeperUniqueID.getUniqueId());
            }
        }, "thread-1").start();

        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                System.out.println(Thread.currentThread().getName() + "分布式唯一ID:" + zookeeperUniqueID.getUniqueId());
            }
        }, "thread-2").start();

        //睡眠，用以保证有充足的时间执行
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

}

2.3 结果

代码执行结果：

 2021-08-20 20:45:59,091 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - 连接成功
 2021-08-20 20:45:59,133 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000060
 thread-2分布式唯一ID:0000000060
2021-08-20 20:45:59,133 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000061
 thread-0分布式唯一ID:0000000061
2021-08-20 20:45:59,135 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000062
 thread-1分布式唯一ID:0000000062
2021-08-20 20:45:59,153 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000063
 thread-2分布式唯一ID:0000000063
2021-08-20 20:45:59,153 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000064
 thread-0分布式唯一ID:0000000064
2021-08-20 20:45:59,177 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000065
 thread-1分布式唯一ID:0000000065
2021-08-20 20:45:59,197 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000066
 thread-2分布式唯一ID:0000000066
2021-08-20 20:45:59,197 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000067
 thread-0分布式唯一ID:0000000067
2021-08-20 20:45:59,221 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000068
 thread-1分布式唯一ID:0000000068
2021-08-20 20:45:59,241 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000069
 thread-2分布式唯一ID:0000000069
2021-08-20 20:45:59,242 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000070
 thread-0分布式唯一ID:0000000070
2021-08-20 20:45:59,265 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000072
 thread-2分布式唯一ID:0000000072
2021-08-20 20:45:59,265 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000073
 thread-0分布式唯一ID:0000000073
2021-08-20 20:45:59,265 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000071
 thread-1分布式唯一ID:0000000071
2021-08-20 20:45:59,289 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000074
 thread-2分布式唯一ID:0000000074
2021-08-20 20:45:59,321 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000075
 thread-0分布式唯一ID:0000000075
2021-08-20 20:45:59,321 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000076
 thread-1分布式唯一ID:0000000076
2021-08-20 20:45:59,323 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000077
 thread-2分布式唯一ID:0000000077
2021-08-20 20:45:59,342 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000078
 thread-0分布式唯一ID:0000000078
2021-08-20 20:45:59,342 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000079
 thread-1分布式唯一ID:0000000079
2021-08-20 20:45:59,343 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000080
 thread-2分布式唯一ID:0000000080
2021-08-20 20:45:59,376 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000081
 thread-0分布式唯一ID:0000000081
2021-08-20 20:45:59,399 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000082
 thread-1分布式唯一ID:0000000082
2021-08-20 20:45:59,400 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000083
 thread-2分布式唯一ID:0000000083
2021-08-20 20:45:59,400 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000084
 thread-0分布式唯一ID:0000000084
2021-08-20 20:45:59,421 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000085
 thread-1分布式唯一ID:0000000085
2021-08-20 20:45:59,422 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000086
 thread-2分布式唯一ID:0000000086
2021-08-20 20:45:59,422 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000087
 thread-0分布式唯一ID:0000000087
2021-08-20 20:45:59,440 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000088
 thread-1分布式唯一ID:0000000088
2021-08-20 20:45:59,510 INFO [cn.duktig.learn.id.ZookeeperUniqueID] - zk创建临时有序节点：/uniqueId/uniqueId0000000089
 thread-1分布式唯一ID:0000000089

Zookeeper Client 查看节点数据：

ZooKeeper 构建分布式唯一ID生成器_第1张图片

分析：

  • 所有ID唯一，无重复
  • 多线程环境下可保证ID自增

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