1.Curator 介紹

• 摘錄官網(wǎng)的介紹
  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.

• 官網(wǎng)地址

2.依賴

<!-- 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  #重試次數(shù)
curator.elapsedTimeMs=5000   #重試間隔時(shí)間
curator.connectString=127.0.0.1:2181   # zookeeper 地址
curator.sessionTimeoutMs=60000  # session超時(shí)時(shí)間
curator.connectionTimeoutMs=5000  # 連接超時(shí)時(shí)間

4.配置類編寫

• 1）配置類

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;

@Configuration
public 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.分布式鎖實(shí)現(xiàn)

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
@Service
public class DistributedLockByZookeeper implements InitializingBean{

    private final static String ROOT_PATH_LOCK = "rootlock";
    private CountDownLatch countDownLatch = new CountDownLatch(1);

    @Autowired
    private CuratorFramework curatorFramework;

    /**
     * 獲取分布式鎖
     */
    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();
                }
            }
        }
    }

    /**
     * 釋放分布式鎖
     */
    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;
    }

    /**
     * 創(chuàng)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("上一個(gè)節(jié)點(diǎn) "+ oldPath + " 已經(jīng)被斷開");
                if (oldPath.contains(path)) {
                    //釋放計(jì)數(shù)器，讓當(dāng)前的請(qǐng)求獲取鎖
                    countDownLatch.countDown();
                }
            }
        });
    }

     //創(chuàng)建父節(jié)點(diǎn)，并創(chuàng)建永久節(jié)點(diǎn)
    @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 事件創(chuàng)建成功");
        } catch (Exception e) {
            log.error("connect zookeeper fail，please check the log >> {}", e.getMessage(), e);
        }
    }
}

6.測試

• 弄兩個(gè) GET 請(qǐng)求測一下，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

• 這個(gè) DistributedLockByZookeeper 中的 afterPropertiesSet 可以使用@Bean的initMethod 初始化創(chuàng)建