curator之zookeeper分布式锁使用

目录

​编辑

1、什么是curator？

2、使用教程

1.1、引用一下jar包

1.2、具体代码

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1、什么是curator？

       Apache curator是Apache ZooKeeper(分布式协调服务)的Java/JVM客户端库。它包括一些高级API框架和实用程序，让开发人员使用Apache ZooKeeper更加容易和可靠。它还包括常用用例和扩展的方法，如服务发现和Java 8异步DSL。

2、使用教程

注意：使用zookeeper自己开发的curator，加锁、释放锁的代码完成不用自己造轮子，拿起来用即可，而且不用考虑下游服务超时导致锁已经释放的问题

1.1、引用一下jar包

    org.apache.curator
    curator-recipes
    4.2.0


    org.apache.curator
    curator-framework
    4.2.0


    org.apache.curator
    curator-client
    5.2.0

1.2、具体代码

package cn.gt.dl.zookeeper.lock;

import com.alibaba.fastjson.JSONObject;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.api.ACLProvider;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.data.ACL;
import org.apache.zookeeper.data.Id;
import org.apache.zookeeper.data.Stat;
import org.junit.Before;
import org.junit.Test;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

/**
 * @author yanshao
 * @date 2022/10/25 5:42 下午
 */
public class ZkExample {

    //zk curator client
    private CuratorFramework curatorFramework;

    //计数器
    private final CountDownLatch countDownLatch = new CountDownLatch(2);

    @Before
    public void curatorFramework() {
        String id = "admin:test";
        String idScheme = "auth";
        String authScheme = "digest";
        String connectString = "127.0.0.1:2181";
        String connectionTimeoutMs = "60000";
        String baseSleepTimeMs = "3000";
        String maxCloseWaitMs = "5000";
        String maxRetries = "3";
        String sessionTimeoutMs = "1000";
        ACLProvider aclProvider = new ACLProvider() {
            private List acl;

            @Override
            public List getDefaultAcl() {
                if (null == acl) {
                    ArrayList acl = ZooDefs.Ids.CREATOR_ALL_ACL;
                    acl.clear();
                    acl.add(new ACL(ZooDefs.Perms.ALL, new Id(idScheme, id)));
                    this.acl = acl;
                }
                return acl;
            }

            @Override
            public List getAclForPath(String path) {
                return acl;
            }
        };
        //为了保证zookeeper中的数据的安全性，避免误操作带来的影响。
        //Zookeeper提供了一套ACL权限控制机制来保证数据的安全。
        CuratorFramework curator = CuratorFrameworkFactory.builder()
                .aclProvider(aclProvider)//防止其它操作误操作节点，加上权限限制
                .authorization(authScheme, id.getBytes())//防止其它操作误操作节点，加上权限限制
                .connectString(connectString)//zk连接串
                .sessionTimeoutMs(Integer.parseInt(sessionTimeoutMs))//session 超时时间
                .connectionTimeoutMs(Integer.parseInt(connectionTimeoutMs)).defaultData("0".getBytes())//连接zk超时时间
                .retryPolicy(new ExponentialBackoffRetry(Integer.parseInt(baseSleepTimeMs), Integer.parseInt(maxRetries)))//连接zk重试次数以及重试间隔时间
                .maxCloseWaitMs(Integer.parseInt(maxCloseWaitMs))//关闭连接等待时间
                .build();
        curator.start();
        this.curatorFramework = curator;
        System.out.println("client已完成初始化");
    }

    @Test
    public void testZkLock() throws InterruptedException {
        //两个线程同时抢锁
        new Thread(() -> {
            try {
                businessMethod1();
            } catch (Exception e) {
                e.printStackTrace();
            }
            //执行完毕之后，计数器减1
            countDownLatch.countDown();
        }).start();

        new Thread(() -> {
            try {
                businessMethod2();
            } catch (Exception e) {
                e.printStackTrace();
            }
            //执行完毕之后，计数器减1
            countDownLatch.countDown();
        }).start();

        //等待两个线程全部完成
        countDownLatch.await();
    }

    public void businessMethod1() throws Exception {
        InterProcessMutex lock = null;
        try {
            String lockKey = "listened_node";
            System.out.println("businessMethod-1>>>开始获取锁");
            lock = lock(lockKey);
            System.out.println("businessMethod-1>>>已获取锁");
            TimeUnit.SECONDS.sleep(10);
        } finally {
            if (Objects.nonNull(lock)) {
                //释放锁
                lock.release();
                System.out.println("businessMethod-1>>>锁已释放");
            }
        }
    }

    @Test
    public void businessMethod2() throws Exception {
        InterProcessMutex lock = null;
        try {
            String lockKey = "listened_node";
            System.out.println("businessMethod-2>>>开始获取锁");
            lock = lock(lockKey);
            System.out.println("businessMethod-2>>>已获取锁");
            TimeUnit.SECONDS.sleep(20);
        } finally {
            if (Objects.nonNull(lock)) {
                lock.release();
                System.out.println("businessMethod-2>>>锁已释放");
            }
        }
    }

    private InterProcessMutex lock(String lockKey) throws Exception {
        //临时顺序节点的根节点
        String lockPath = "/lock1/" + lockKey;

        //申明可重入锁
        InterProcessMutex lock = new InterProcessMutex(curatorFramework, lockPath);

        //这里的acquire方法是阻塞方法，超时时间是3分钟
        if (lock.acquire(3, TimeUnit.MINUTES)) {
            System.out.println("节点列表>>>" + lock.getParticipantNodes());
            Stat stat = curatorFramework.checkExists().forPath(lockPath);
            if (null != stat) {
                System.out.println(lockPath + "节点信息>>>" + JSONObject.toJSONString(stat));
            }
        }
        //返回lock，说明成功获取到锁
        return lock;
    }
}

运行结果：

      代码有较详细的注释，核心代码就这三行，curator完全封装好了，我们只需要“傻瓜”式的使用，而且curator fluent风格的api，也非常OK。