Zookeeper4：Java客户端、应用场景以及实现、第三方客户端curator工具包

文章目录

- Java连接Zookeeper服务端
- - 依赖
  - 代码使用
- 应用场景
- - 统一命名服务
  - 统一配置管理
  - 统一集群管理
  - 服务器节点动态上下线
  - - 理解
    - 实现
    - - 模拟服务提供者【客户端代码】-注册服务
      - 模拟服务消费者【客户端代码】-获取服务信息进行请求消费
  - 软负载均衡
  - 分布式锁
  - - 理解
    - 实现
  - 生产集群安装N台机器合适
- 第三方基于zookeeper的包
- - curator
  - - 依赖
    - 代码

Java连接Zookeeper服务端

文档： https://zookeeper.apache.org/doc/r3.9.1/javaExample.html

依赖

  <dependencies>

    <!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
    <dependency>
      <groupId>org.apache.zookeeper</groupId>
      <artifactId>zookeeper</artifactId>
      <version>3.9.1</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.dromara.hutool/hutool-all -->
    <dependency>
      <groupId>org.dromara.hutool</groupId>
      <artifactId>hutool-all</artifactId>
      <version>6.0.0-M11</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/junit/junit -->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.2</version>
    </dependency>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-api</artifactId>
      <version>5.10.2</version>
    </dependency>



    <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.30</version>
      <scope>provided</scope>
    </dependency>


  </dependencies>

代码使用

Java代码

public class ZkClient {

    @Test
    @SneakyThrows
    public void test1() {
        String connectString = "192.168.19.107:2181"; // zookeeper服务端信息
        int sessionTimeout = 2000; // 连接最大时长（毫秒）
        ZooKeeper zooKeeperClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            public void process(WatchedEvent event) {
                Console.log("服务端推送给客户端的监听事件信息 == {}", event);
            }
        });

        // 监听节点数据的变化 === 等价于get -w 命令
        try {
            String s = zooKeeperClient.create("/test", "testData".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            Console.log("创建节点成功：{}", s);
        } catch (Exception e) {
            Console.log("创建节点失败：{}", e.getMessage());
        }


        // 启动监听增删子节点的变化，然后在前面【Watcher】能收到监听事件 === 等价于ls -w 命令
        List<String> children = zooKeeperClient.getChildren("/test", true);
        Console.log("Zookeeper服务端当前/test所有的子节点名字：{}", children);

        //启动节点的状态信息变化 === 等价于stat -w 命令
        Stat statInfo = zooKeeperClient.exists("/test", true);
        Console.log("Zookeeper服务端当前/test节点的状态信息：{}" , statInfo);



        //程序永远不结束
        while (true) {
            try {
                Thread.sleep(1000); // 暂停1秒钟
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

}

1. 前提背景
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2. 开始执行代码
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3. 命令增加节点
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4. Java客户端监听到的消息
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应用场景

统一命名服务

对应用、服务同意命名便于识别，比如一个对外服务接口的多集群，则需要统一的管理同一服务的所有IP

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统一配置管理

场景：

一般要求一个集群中，所有节点的配置信息是一致的，比如Kafka集群。
对配置文件修改后，希望能够快速同步到各个节点上
实现：配置信息写入到Zookeeper一个节点中，客户端监听这个节点即可

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统一集群管理

场景：

分布式环境，实时掌握每个节点状态是必要的
实现：节点信息写入ZooKeeper_上的一个ZNode。客户端监听这个ZNode可获取它的实时状态变化

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服务器节点动态上下线

理解

特点： 客户端能实时洞察到服务器上下线的变化

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实现

前提： 运行代码前自行在Zookeeper客户端创建/service节点【create /service “service”】，因为zookeeper创建子节点前必须有父节点，否则创建子节点失败

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模拟服务提供者【客户端代码】-注册服务

public class ServiceProviderZkClient {

    private static String connecting = StrUtil.join(StrUtil.COMMA,"192.168.19.107:2181","192.168.19.108:2181","192.168.19.109:2181");
    private static Integer timeout = 2000;

    @SneakyThrows
    public static void main(String[] args) {








        Arrays.asList("application1","application2","application3").stream()
                .parallel()
                .forEach(applicationName -> {

                    serviceRegister(applicationName);

                });


    }

    @SneakyThrows
    public static void serviceRegister(String applicationName) {

        ZooKeeper zooKeeper = new ZooKeeper(connecting, timeout, new Watcher() {
            public void process(WatchedEvent event) {
                Console.log("服务端推送的监听信息：{}", event);
            }
        });

        String zookeeperPath = StrUtil.format("/service/{}", applicationName);
        byte[] zookeeperPathData = Convert.toPrimitiveByteArray(StrUtil.format("{}应用的IP地址等信息", applicationName));


        String newNodePath = zooKeeper.create(zookeeperPath, zookeeperPathData, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);


        Console.log("【{}】在线" , applicationName);


        //程序永远不结束
        while (true) {
            try {
                Thread.sleep(1000); // 暂停1秒钟
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }

}

模拟服务消费者【客户端代码】-获取服务信息进行请求消费

public class ServiceProviderConsumerZkClient {

    private static String connecting = StrUtil.join(StrUtil.COMMA,"192.168.19.107:2181","192.168.19.108:2181","192.168.19.109:2181");
    private static Integer timeout = 2000;

    private static AtomicReference children = new AtomicReference(ListUtil.of());
    private static ZooKeeper zooKeeper = null;

    @SneakyThrows
    public static void main(String[] args) {



        zooKeeper = new ZooKeeper(connecting, timeout, new Watcher() {
            public void process(WatchedEvent event) {
                Console.log("服务端推送的监听信息：{}", event);

                //每次收到监听通知消息，同步服务在线状态
                getServiceNode();
            }
        });


        //获取在线中的提供提供者
        getServiceNode();


        while (true) {

            String targetServiceName = "application2";

            //在线的服务真实路径
            String targetServiceNodeName = CollUtil.emptyIfNull((List<String>)children.get())
                    .stream()
                    .filter(childrenPath -> StrUtil.contains(childrenPath, targetServiceName))
                    .findFirst()
                    .orElse(null);
            String targetServiceNamePath = StrUtil.format("/service/{}" , targetServiceNodeName);
            boolean targetServiceNameExistFlag = StrUtil.isNotBlank(targetServiceNodeName);

            if(targetServiceNameExistFlag) {

                //获取服务的配置信息进行服务调用 == 节点里面一般包含当前服务提供者http，端口等等信息
                String nodeData = Convert.toStr(zooKeeper.getData(targetServiceNamePath, false, null));
                Console.log("【{}】第三方服务上线，调用接口成功", targetServiceName);
            }else {
                Console.log("【{}】第三方服务未上线，调用接口失败" , targetServiceName);
            }


            ThreadUtil.sleep(5000);
        }


    }

    @SneakyThrows
    public static void getServiceNode() {
        children.set(zooKeeper.getChildren("/service", true));
        Console.log("系统中的服务提供者节点：{}" , children.get());
    }

}

服务提供者进行注册服务时
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服务消费者进行消费时
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软负载均衡

特点： 在Zookeepert中记录每台服务器的访问数，让访问数最少的服务器去处理最新的客户端请求

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分布式锁

理解

概念： 分布式系统中能保证多个进程有序地进行访问临界资源的锁，拿到锁的进程才可以访问资源，否则一直排队等待锁

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实现

public class DistributedLock {

    private static String connecting = StrUtil.join(StrUtil.COMMA, "192.168.19.107:2181", "192.168.19.108:2181", "192.168.19.109:2181");
    private static Integer timeout = 2000;
    private static ZooKeeper zooKeeper;
    private static String parentPath = "/DistributedLock";
    private static Map<String, CountDownLatch> threadIdToCountDownLatchMap = MapUtil.newSafeConcurrentHashMap();


    static {
        init();
    }

    @SneakyThrows
    private static void init() {
        zooKeeper = connectZooKeeper();

        // 创建锁父节点
        String realParentPath = zooKeeper.create(parentPath, Convert.toPrimitiveByteArray(parentPath), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

        // 监听父节点下子节点增删的变化
        // List<String> sonNodeNames = getParentSortedNodes(true);
    }

    @SneakyThrows
    private static ZooKeeper connectZooKeeper() {
        ZooKeeper connectedZooKeeper = new ZooKeeper(connecting, timeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                Console.log("zookeeper收到服务端监听通知消息：{}", event);
                String dealNodePath = event.getPath();
                Event.EventType eventType = event.getType();

                if (eventType == Event.EventType.NodeDeleted) {
                    String nodeBelongThreadId = StrUtil.subBefore(StrUtil.subAfter(dealNodePath, "/", true), "_", false);
                    Console.log("收到删除节点通知，释放线程等待 == {}", nodeBelongThreadId);
                    // 释放锁
                    CountDownLatch countDownLatch = threadIdToCountDownLatchMap.get(nodeBelongThreadId);
                    if (countDownLatch != null) {
                        countDownLatch.countDown();
                        threadIdToCountDownLatchMap.remove(nodeBelongThreadId);
                    }
                }

            }
        });
        return connectedZooKeeper;
    }

    @SneakyThrows
    public static List<String> getParentSortedNodes(Boolean watchFlag) {
        List<String> sonNodeNames = CollUtil.emptyIfNull(zooKeeper.getChildren(parentPath, true))
                .stream()
                .sorted(CompareUtil::compare)
                .collect(Collectors.toList());

        return sonNodeNames;
    }


    /**
     * 获取锁
     */
    @SneakyThrows
    public static void acquireLock() {

        // 当前锁的节点前缀
        String nodeNamePrefix = Thread.currentThread().getId() + "_";
        // 当前锁的节点完整领前缀
        String absolutenodeNamePathPrefix = StrUtil.format("{}/{}", parentPath, nodeNamePrefix);


        // 完整的前缀
        String realAbsolutenodeNamePath = zooKeeper.create(absolutenodeNamePathPrefix, Convert.toPrimitiveByteArray("absolutenodeNamePathPrefix"), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);


        // 获取当前父路径下的所有节点
        List<String> sonNodeNames = getParentSortedNodes(false);
        if (CollUtil.size(sonNodeNames) == 1) { // 获取锁
            Console.log("【子元素为1】获取锁【{}】",realAbsolutenodeNamePath);
            return;
        } else {
            String firstNodeName = CollUtil.getFirst(sonNodeNames);

            if (StrUtil.startWith(firstNodeName, nodeNamePrefix)) {
                Console.log("【当前子节点在排序后序列为第一个】获取锁【{}】",realAbsolutenodeNamePath);
                return;
            } else {
                // 一直等待直到有机会获取锁
                CountDownLatch countDownLatch = new CountDownLatch(1);


                // 监听该节点的前一个节点的增删变化
                int currentNodeIndex = CollUtil.indexOf(sonNodeNames, nodeName -> StrUtil.endWith(realAbsolutenodeNamePath, nodeName));
                String previousNodeName = CollUtil.get(sonNodeNames, currentNodeIndex - 1);
                String previousNodePath = StrUtil.format("{}/{}", parentPath, previousNodeName);
                zooKeeper.getData(previousNodePath, true, null);
                threadIdToCountDownLatchMap.put(StrUtil.subBefore(previousNodeName,"_", false), countDownLatch);

                countDownLatch.await();
                Console.log("获取锁【{}】", realAbsolutenodeNamePath);
            }
        }

    }

    /**
     * 释放锁
     */
    @SneakyThrows
    public static void releaseLock() {
        String currentThreadId = Convert.toStr(Thread.currentThread().getId());

        // CountDownLatch countDownLatch = threadIdToCountDownLatchMap.get(currentThreadId);
        // if (ObjUtil.isNull(countDownLatch)) {
        //     Console.log("当前线程并没有等待锁的操作");
        //     return;
        // }

        // 当前锁的节点前缀
        String nodeNamePrefix = currentThreadId + "_";

        String realNodeName = getParentSortedNodes(false).stream()
                .filter(nodeName -> StrUtil.startWith(nodeName, nodeNamePrefix))
                .findFirst()
                .orElse(null);

        if (StrUtil.isBlank(realNodeName)) {
            Console.log("当前线程并未有获取锁的操作");
            return;
        }

        String completeNodePath = StrUtil.format("{}/{}", parentPath, realNodeName);

        zooKeeper.delete(completeNodePath, -1);
        Console.log("释放锁【{}】", completeNodePath);
    }


    public static void main(String[] args) {
        String s = StrUtil.subAfter("fsd/fdsfsdfds", "/", true);
        Console.log(s);
    }
}

public class App2Test {



    @Test
    @SneakyThrows
    public void test3() {

        Bean publicBean = new Bean();

        List<Thread> threadGroup = ListUtil.of();

        for (int i = 0; i < 10; i++) {

            Thread newThread = new Thread(() -> {
                DistributedLock.acquireLock();

                // 随机等待
                try {
                    Thread.sleep(RandomUtil.randomInt(1000, 3000));
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }

                publicBean.num = ++publicBean.num;
                Console.log("【{}】：数+1处理 == {}", Thread.currentThread().getId(), publicBean.num);

                DistributedLock.releaseLock();
            });

            newThread.start();

            threadGroup.add(newThread);
        }


        for (Thread runThread : threadGroup) {
            // 等待线程运行完
            runThread.join();
        }


        Console.log("公共数据最终的结果：{}", publicBean.num);
        Assert.equals(publicBean.num, 10);

    }
}

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生产集群安装N台机器合适

特点： 好处提高可靠性、坏处数据同步有延迟

第三方基于zookeeper的包

curator

官网： https://curator.apache.org/docs/about

入门教程： https://curator.apache.org/docs/getting-started/

依赖

    <!-- https://mvnrepository.com/artifact/org.apache.curator/curator-framework -->
    <dependency>
      <groupId>org.apache.curator</groupId>
      <artifactId>curator-framework</artifactId>
      <version>5.6.0</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.curator/curator-recipes -->
    <dependency>
      <groupId>org.apache.curator</groupId>
      <artifactId>curator-recipes</artifactId>
      <version>5.6.0</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.curator/curator-client -->
    <dependency>
      <groupId>org.apache.curator</groupId>
      <artifactId>curator-client</artifactId>
      <version>5.6.0</version>
    </dependency>

代码

发现： 运行代码可见curator的分布式锁的原理跟前面自己实现的逻辑差不多，都是通过增、删子节点，然后监控前一个节点被删释放锁的逻辑原理去做的

public class OtherTest {



    @Test
    @SneakyThrows
    public void test2() {

        String connectString = "192.168.19.107:2181,192.168.19.108:2181,192.168.19.109:2181";
        RetryOneTime retryOneTime = new RetryOneTime(2000);

        CuratorFramework curatorFramework = CuratorFrameworkFactory.newClient(connectString, 60 * 1000 * 10, 15 * 1000 * 10, retryOneTime);
        curatorFramework.start();

        //获取某父目录旗下的亲儿子节点名字信息
        List<String> sonNodeNames = curatorFramework.getChildren().forPath("/");
        Console.log(sonNodeNames);

		
		// 分布式锁
        InterProcessMutex interProcessMutexLock = new InterProcessMutex(curatorFramework, "/CuratorLock");

        App2Test.Bean publicBean = new App2Test.Bean();
        List<Thread> threadGroup = ListUtil.of();
        for (int i = 0; i < 5; i++) {

            Thread newThread = new Thread(() -> {
                try {
                    interProcessMutexLock.acquire();

                    // 随机等待
                    try {
                        Thread.sleep(RandomUtil.randomInt(1000, 3000));
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }

                    publicBean.num = ++publicBean.num;
                    Console.log("【{}】：数+1处理 == {}", Thread.currentThread().getId(), publicBean.num);

                }catch (Exception e) {

                }finally {
                    try {
                        interProcessMutexLock.release();
                    }catch (Exception e) {

                    }
                }
            });

            newThread.start();

            threadGroup.add(newThread);
        }

        for (Thread runThread : threadGroup) {
            // 等待线程运行完
            runThread.join();
        }


        Console.log("公共数据最终的结果：{}", publicBean.num);
        Assert.equals(publicBean.num, 5);



    }

}