基于Zookeeper的瞬时节点实现分布式锁

1、Zookeeper的数据结构

 

 

 

 

二、zookeeper分布式锁原理

 

二、zookeeper分布式锁代码实现

 1、maven依赖 

    （1）https://mvnrepository.com/   搜索 zookeeper

    （2）选择安装的对应版本

         

      (3) pom 文件 添加依赖

   

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.6.1</version>
</dependency>

 2、核心类 ZkLock

    实现监控Watcher和自动关闭AutoCloseable 接口

  

package com.example.distributezklock.lock;

import lombok.extern.slf4j.Slf4j;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.io.IOException;
import java.util.Collections;
import java.util.List;

@Slf4j
public class ZkLock implements AutoCloseable, Watcher {

    private ZooKeeper zooKeeper;
    private String znode;

    public ZkLock() throws IOException {
        this.zooKeeper = new ZooKeeper("localhost:2181",
                10000,this);
    }

    public boolean getLock(String businessCode) {
        try {
            //创建业务 根节点
            Stat stat = zooKeeper.exists("/" + businessCode, false);
            if (stat==null){
                zooKeeper.create("/" + businessCode,businessCode.getBytes(),
                        ZooDefs.Ids.OPEN_ACL_UNSAFE,
                        CreateMode.PERSISTENT);
            }

            //创建瞬时有序节点  /order/order_00000001
            znode = zooKeeper.create("/" + businessCode + "/" + businessCode + "_", businessCode.getBytes(),
                    ZooDefs.Ids.OPEN_ACL_UNSAFE,
                    CreateMode.EPHEMERAL_SEQUENTIAL);

            //获取业务节点下 所有的子节点
            List<String> childrenNodes = zooKeeper.getChildren("/" + businessCode, false);
            //子节点排序
            Collections.sort(childrenNodes);
            //获取序号最小的（第一个）子节点
            String firstNode = childrenNodes.get(0);
            //如果创建的节点是第一个子节点，则获得锁
            if (znode.endsWith(firstNode)){
                return true;
            }
            //不是第一个子节点，则监听前一个节点
            String lastNode = firstNode;
            for (String node:childrenNodes){
                if (znode.endsWith(node)){
                    zooKeeper.exists("/"+businessCode+"/"+lastNode,true);
                    break;
                }else {
                    lastNode = node;
                }
            }
            synchronized (this){
                wait();
            }

            return true;

        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }





    @Override
    public void close() throws Exception {
        zooKeeper.delete(znode,-1);
        zooKeeper.close();
        log.info("我已经释放了锁！");
    }

    @Override
    public void process(WatchedEvent event) {
        if (event.getType() == Event.EventType.NodeDeleted){
            synchronized (this){
                notify();
            }
        }
    }
}

3、Controller测试

  

package com.example.distributezklock.controller;

import com.example.distributezklock.lock.ZkLock;
import lombok.extern.slf4j.Slf4j;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

@RestController
@Slf4j
public class ZookeeperController {
    @Autowired
    private CuratorFramework client;

    @RequestMapping("zkLock")
    public String zookeeperLock(){
        log.info("我进入了方法！");
        try (ZkLock zkLock = new ZkLock()) {
            if (zkLock.getLock("order")){
                log.info("我获得了锁");
                Thread.sleep(10000);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        log.info("方法执行完成！");
        return "方法执行完成！";
    }

    @RequestMapping("curatorLock")
    public String curatorLock(){
        log.info("我进入了方法！");
        InterProcessMutex lock = new InterProcessMutex(client, "/order");
        try{
            if (lock.acquire(30, TimeUnit.SECONDS)){
                log.info("我获得了锁！！");
                Thread.sleep(10000);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                log.info("我释放了锁！！");
                lock.release();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        log.info("方法执行完成！");
        return "方法执行完成！";
    }
}

4、Test测试

package com.example.distributezklock;

import com.example.distributezklock.lock.ZkLock;
import lombok.extern.slf4j.Slf4j;
import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j
public class DistributeZkLockApplicationTests {

    @Test
    public void contextLoads() {
    }


    @Test
    public void testZkLock() throws Exception {
        ZkLock zkLock = new ZkLock();
        boolean lock = zkLock.getLock("order");
        log.info("获得锁的结果："+lock);

        zkLock.close();
    }

}