SpringBoot集成Curator实现分布式锁

1.Curator 介绍

• 摘录官网的介绍
  Apache Curator is a Java/JVM client library for Apache ZooKeeper, a distributed coordination service. It includes a highlevel API framework and utilities to make using Apache ZooKeeper much easier and more reliable. It also includes recipes for common use cases and extensions such as service discovery and a Java 8 asynchronous DSL.

• 官网地址

2.依赖

<!-- zookeeper --><dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.10</version></dependency><dependency>
     <groupId>org.apache.curator</groupId>
     <artifactId>curator-framework</artifactId>
     <version>2.12.0</version></dependency><dependency>
     <groupId>org.apache.curator</groupId>
     <artifactId>curator-recipes</artifactId>
     <version>2.12.0</version></dependency>

3.配置文件

• application.properties 中添加如下配置

curator.retryCount=5  #重试次数curator.elapsedTimeMs=5000   #重试间隔时间curator.connectString=127.0.0.1:2181   # zookeeper 地址curator.sessionTimeoutMs=60000  # session超时时间curator.connectionTimeoutMs=5000  # 连接超时时间

4.配置类编写

• 1）配置类

package com.zxr.micro.config.zookeeper;import lombok.Data;import org.springframework.boot.context.properties.ConfigurationProperties;import org.springframework.stereotype.Component;@Data@Component@ConfigurationProperties(prefix = "curator")public class WrapperZk {    private int retryCount;    private int elapsedTimeMs;    private String connectString;    private int sessionTimeoutMs;    private int connectionTimeoutMs;
}

• 2）配置中心

package com.zxr.micro.config.zookeeper;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.retry.RetryNTimes;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;

@Configurationpublic class ZkConfiguration {

    @Autowired
    WrapperZk wrapperZk;

    @Bean(initMethod = "start")
    public CuratorFramework curatorFramework() {        return CuratorFrameworkFactory.newClient(                wrapperZk.getConnectString(),                wrapperZk.getSessionTimeoutMs(),                wrapperZk.getConnectionTimeoutMs(),                new RetryNTimes(wrapperZk.getRetryCount(), wrapperZk.getElapsedTimeMs()));
    }
}

5.分布式锁实现

package com.zxr.micro.config.zookeeper;import lombok.extern.slf4j.Slf4j;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.recipes.cache.PathChildrenCache;import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.ZooDefs;import org.springframework.beans.factory.InitializingBean;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import java.util.concurrent.CountDownLatch;@Slf4j@Servicepublic class DistributedLockByZookeeper implements InitializingBean{    private final static String ROOT_PATH_LOCK = "rootlock";    private CountDownLatch countDownLatch = new CountDownLatch(1);    @Autowired
    private CuratorFramework curatorFramework;    /**
     * 获取分布式锁
     */
    public void acquireDistributedLock(String path) {
        String keyPath = "/" + ROOT_PATH_LOCK + "/" + path;        while (true) {            try {
                curatorFramework
                        .create()
                        .creatingParentsIfNeeded()
                        .withMode(CreateMode.EPHEMERAL)
                        .withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)
                        .forPath(keyPath);
                log.info("success to acquire lock for path:{}", keyPath);                break;
            } catch (Exception e) {
                log.info("failed to acquire lock for path:{}", keyPath);
                log.info("while try again .......");                try {                    if (countDownLatch.getCount() <= 0) {
                        countDownLatch = new CountDownLatch(1);
                    }
                    countDownLatch.await();
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
            }
        }
    }    /**
     * 释放分布式锁
     */
    public boolean releaseDistributedLock(String path) {        try {
            String keyPath = "/" + ROOT_PATH_LOCK + "/" + path;            if (curatorFramework.checkExists().forPath(keyPath) != null) {
                curatorFramework.delete().forPath(keyPath);
            }
        } catch (Exception e) {
            log.error("failed to release lock");            return false;
        }        return true;
    }    /**
     * 创建 watcher 事件
     */
    private void addWatcher(String path) throws Exception {
        String keyPath;        if (path.equals(ROOT_PATH_LOCK)) {
            keyPath = "/" + path;
        } else {
            keyPath = "/" + ROOT_PATH_LOCK + "/" + path;
        }        final PathChildrenCache cache = new PathChildrenCache(curatorFramework, keyPath, false);
        cache.start(PathChildrenCache.StartMode.POST_INITIALIZED_EVENT);
        cache.getListenable().addListener((client, event) -> {            if (event.getType().equals(PathChildrenCacheEvent.Type.CHILD_REMOVED)) {
                String oldPath = event.getData().getPath();
                log.info("上一个节点 "+ oldPath + " 已经被断开");                if (oldPath.contains(path)) {                    //释放计数器，让当前的请求获取锁
                    countDownLatch.countDown();
                }
            }
        });
    }     //创建父节点，并创建永久节点
    @Override
    public void afterPropertiesSet() {
        curatorFramework = curatorFramework.usingNamespace("lock-namespace");
        String path = "/" + ROOT_PATH_LOCK;        try {            if (curatorFramework.checkExists().forPath(path) == null) {
                curatorFramework.create()
                        .creatingParentsIfNeeded()
                        .withMode(CreateMode.PERSISTENT)
                        .withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)
                        .forPath(path);
            }
            addWatcher(ROOT_PATH_LOCK);
            log.info("root path 的 watcher 事件创建成功");
        } catch (Exception e) {
            log.error("connect zookeeper fail，please check the log >> {}", e.getMessage(), e);
        }
    }
}

6.测试

• 弄两个 GET 请求测一下，看看效果

package com.zxr.micro.controller;import com.zxr.micro.common.RespMsg;import com.zxr.micro.config.zookeeper.DistributedLockByZookeeper;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;@RestController@RequestMapping("/hello")public class MicroController {    @Autowired
    private DistributedLockByZookeeper distributedLockByZookeeper;    private final static String PATH = "test";    @GetMapping("/lock1")    public RespMsg<Boolean> getLock1() {
        Boolean flag;
        distributedLockByZookeeper.acquireDistributedLock(PATH);        try {
            Thread.sleep(20000);
        } catch (InterruptedException e) {
            e.printStackTrace();
            flag = distributedLockByZookeeper.releaseDistributedLock(PATH);
        }
        flag = distributedLockByZookeeper.releaseDistributedLock(PATH);        return RespMsg.success(flag);
    }    @GetMapping("/lock2")    public RespMsg getLock2() {
        Boolean flag;
        distributedLockByZookeeper.acquireDistributedLock(PATH);        try {
            Thread.sleep(15000);
        } catch (InterruptedException e) {
            e.printStackTrace();
            flag = distributedLockByZookeeper.releaseDistributedLock(PATH);
        }
        flag = distributedLockByZookeeper.releaseDistributedLock(PATH);        return RespMsg.success(flag);
    }
}

7.注意

• 这个 DistributedLockByZookeeper 中的 afterPropertiesSet 可以使用@Bean的initMethod 初始化创建

作者：移动的红烧肉
链接：https://www.jianshu.com/p/df99f8a371ae