Redis系列之简单实现watchDog自动续期机制

在分布锁的实际使用中，可能会遇到一种情况，一个业务执行时间很长，已经超过redis加锁的时间，也就是锁已经释放了，但是业务还没执行完成，这时候其它线程还是可以获取锁，那就没保证线程安全

项目环境：

• JDK 1.8

• SpringBoot 2.2.1

• Maven 3.2+

• Mysql 8.0.26

• spring-boot-starter-data-redis 2.2.1

• jedis3.1.0

• 开发工具

  • IntelliJ IDEA

  • smartGit

先搭建一个springboot集成jedis的例子工程，参考我之前的博客，

抽象类，实现一些共用的逻辑

package com.example.jedis.common;

import lombok.extern.slf4j.Slf4j;

import java.net.SocketTimeoutException;
import java.util.concurrent.TimeUnit;

import static com.example.jedis.common.RedisConstant.DEFAULT_EXPIRE;
import static com.example.jedis.common.RedisConstant.DEFAULT_TIMEOUT;

@Slf4j
public abstract class AbstractDistributedLock implements DistributedLock {

    @Override
    public boolean acquire(String lockKey, String requestId, int expireTime, int timeout) {
        expireTime = expireTime <= 0 ? DEFAULT_EXPIRE : expireTime;
        timeout = timeout < 0 ? DEFAULT_TIMEOUT : timeout * 1000;

        long start = System.currentTimeMillis();
        try {
            do {
                if (doAcquire(lockKey, requestId, expireTime)) {
                    watchDog(lockKey, requestId, expireTime);
                    return true;
                }
                TimeUnit.MILLISECONDS.sleep(100);
            } while (System.currentTimeMillis() - start < timeout);

        } catch (Exception e) {
            Throwable cause = e.getCause();
            if (cause instanceof SocketTimeoutException) {
                // ignore exception
                log.error("sockTimeout exception:{}", e);
            }
            else if (cause instanceof  InterruptedException) {
                // ignore exception
                log.error("Interrupted exception:{}", e);
            }
            else {
                log.error("lock acquire exception:{}", e);
            }
            throw new LockException(e.getMessage(), e);
        }
        return false;
    }

    @Override
    public boolean release(String lockKey, String requestId) {
        try {
            return doRelease(lockKey, requestId);
        } catch (Exception e) {
            log.error("lock release exception:{}", e);
            throw new LockException(e.getMessage(), e);
        }
    }

    protected abstract boolean doAcquire(String lockKey, String requestId, int expireTime);

    protected abstract boolean doRelease(String lockKey, String requestId);

    protected abstract void watchDog(String lockKey, String requestId, int expireTime);


}

具体的实现，主要是基于一个定时任务，时间间隔一定要比加锁时间少一点，这里暂时少1s，加上一个lua脚本进行检测，检测不到数据，就关了定时任务

package com.example.jedis.common;

import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.convert.Convert;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

@Component
@Slf4j
public class JedisLockTemplate extends AbstractRedisLock implements InitializingBean {

    private String UNLOCK_LUA = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";

    private String WATCH_DOG_LUA = "local lock_key=KEYS[1]\n" +
            "local lock_value=ARGV[1]\n" +
            "local lock_ttl=ARGV[2]\n" +
            "local current_value=redis.call('get',lock_key)\n" +
            "local result=0\n" +
            "if lock_value==current_value then\n" +
            "    redis.call('expire',lock_key,lock_ttl)\n" +
            "    result=1\n" +
            "end\n" +
            "return result";

    private static final Long UNLOCK_SUCCESS = 1L;

    private static final Long RENEWAL_SUCCESS = 1L;

    @Autowired
    private JedisTemplate jedisTemplate;

    private ScheduledThreadPoolExecutor scheduledExecutorService;


    @Override
    public void afterPropertiesSet() throws Exception {
        this.UNLOCK_LUA = jedisTemplate.scriptLoad(UNLOCK_LUA);
        this.WATCH_DOG_LUA = jedisTemplate.scriptLoad(WATCH_DOG_LUA);
        scheduledExecutorService = new ScheduledThreadPoolExecutor(1);
    }


    @Override
    public boolean doAcquire(String lockKey, String requestId, int expire) {
        return jedisTemplate.setnxex(lockKey, requestId, expire);
    }

    @Override
    public boolean doRelease(String lockKey, String requestId) {
        Object eval = jedisTemplate.evalsha(UNLOCK_LUA, CollUtil.newArrayList(lockKey), CollUtil.newArrayList(requestId));
        if (UNLOCK_SUCCESS.equals(eval)) {
            scheduledExecutorService.shutdown();
            return true;
        }
        return false;
    }

    @Override
    public void watchDog(String lockKey, String requestId, int expire) {
        int period = getPeriod(expire);
        if (scheduledExecutorService.isShutdown()) {
            scheduledExecutorService = new ScheduledThreadPoolExecutor(1);
        }
        scheduledExecutorService.scheduleAtFixedRate(
                new WatchDogTask(scheduledExecutorService, CollUtil.newArrayList(lockKey), CollUtil.newArrayList(requestId, Convert.toStr(expire))),
                1,
                period,
                TimeUnit.SECONDS
                );
    }

    class WatchDogTask implements Runnable {

        private ScheduledThreadPoolExecutor scheduledThreadPoolExecutor;
        private List<String> keys;
        private List<String> args;

        public WatchDogTask(ScheduledThreadPoolExecutor scheduledThreadPoolExecutor, List<String> keys, List<String> args) {
            this.scheduledThreadPoolExecutor = scheduledThreadPoolExecutor;
            this.keys = keys;
            this.args = args;
        }

        @Override
        public void run() {
            log.info("watch dog for renewal...");
            Object evalsha = jedisTemplate.evalsha(WATCH_DOG_LUA, keys, args);
            if (!evalsha.equals(RENEWAL_SUCCESS)) {
                scheduledThreadPoolExecutor.shutdown();
            }
            log.info("renewal result:{}, keys:{}, args:{}", evalsha, keys, args);
        }
    }

    private int getPeriod(int expire) {
        if (expire < 1)
            throw new LockException("expire不允许小于1");
        return expire - 1;
    }



}

写一个测试Controller类，开始用SpringBoot测试类的，但是发现有时候还是经常出现一些连接超时情况，这个可能是框架兼容的bug

package com.example.jedis.controller;

import com.example.jedis.common.JedisLockTemplate;
import com.example.jedis.common.Lock;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.stream.IntStream;

@RestController
@Slf4j
public class TestController {


    private static final String REDIS_KEY = "test:lock";

    @Autowired
    private JedisLockTemplate jedisLockTemplate;

    @GetMapping("test")
    public void test(@RequestParam("threadNum")Integer threadNum) throws InterruptedException {

        CountDownLatch countDownLatch = new CountDownLatch(threadNum);
        IntStream.range(0, threadNum).forEach(e->{
            new Thread(new RunnableTask(countDownLatch)).start();
        });
        countDownLatch.await();


    }

    @GetMapping("testLock")
    @Lock(lockKey = "test:api", requestId = "123", expire = 5, timeout = 3)
    public void testLock() throws InterruptedException {
        doSomeThing();
    }

    class RunnableTask implements Runnable {

        CountDownLatch countDownLatch;

        public RunnableTask(CountDownLatch countDownLatch) {
            this.countDownLatch = countDownLatch;
        }

        @Override
        public void run() {
            redisLock();
            countDownLatch.countDown();
        }


    }


    private void redisLock() {
        String requestId = getRequestId();
        Boolean lock = jedisLockTemplate.acquire(REDIS_KEY, requestId, 5, 3);
        if (lock) {
            try {
                doSomeThing();
            } catch (Exception e) {
                jedisLockTemplate.release(REDIS_KEY, requestId);
            } finally {
                jedisLockTemplate.release(REDIS_KEY, requestId);
            }
        } else {
            log.warn("获取锁失败!");
        }
    }

    private void doSomeThing() throws InterruptedException {
        log.info("do some thing");
        Thread.sleep(15 * 1000);
    }

    private String getRequestId() {
        String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        Random random=new Random();
        StringBuffer sb=new StringBuffer();
        for(int i=0;i<32;i++){
            int number=random.nextInt(62);
            sb.append(str.charAt(number));
        }
        return sb.toString();

    }



}

# 模拟100个并发请求
curl http://127.0.0.1:8080/springboot-jedis/test?threadNum=100

长事务还没执行完成，会自动进行续期

模拟100个线程的场景，只有一个线程会获取到锁

参考资料：

• https://github.com/finefuture/RedisLock-with-WatchDog/blob/master/RedisLock.java
  
• https://www.cnblogs.com/crazymakercircle/p/14731826.html
• https://blog.csdn.net/Cocoxzq000/article/details/121575272