分布式Redis锁 - RedissonClient

时间：2025-03-10 10:14:27
Redis Java Client选型-Jedis Lettuce Redisson
最常用的可重入锁（Reentrant Lock） 先写个单元测试试一下
public class RedisLockTest {

    private RedissonClient redissonClient;

    //请求的key
    private static final String demo ="u001";

    //模拟短时间内的并发请求量

    private static final int threadNum =5;

    @Before
    public void init(){
        Config config = new Config();
        ().setAddress("redis://120.78.144.70:6379");
         = (config);

        (().getName()+"是否存在key"+(demo).isExists());
    }

    private class UserRequest implements Runnable{

        private CountDownLatch cdl;

        public UserRequest(CountDownLatch latch){
            =latch;
        }

        @Override
        public void run() {
            try {
                if ((demo).tryLock(0L,-1L, )) {
                    (().getName()+"获取锁成功");
                    (5000);
                    (demo).unlock();
                    (().getName()+"释放锁成功");
                }else{
                    (().getName()+"获取锁失败"+"是否存在key"+(demo).isExists());
                }
            }catch (Exception e) {
                ();
            }finally {
                //倒计时计数一次
                ();
            }
        }
    }

    @Test
    public void testRedissonLock(){
        CountDownLatch cdl=new CountDownLatch(threadNum);
        Executor executor = (threadNum);
        try{
            for (int i =0; i< threadNum; i++) {
                if(i==2){
                    //模拟在业务代码没执行完毕时另一个线程获取锁
                    (1500);
                }
                (new UserRequest(cdl));
            }
            //阻塞主线程，等待所有的子线程执行完毕
            ();
        }catch (Exception e){
            ();
        }
    }
}

分布式锁的实现分析参考
/p/a8b3473f9c24

比较关注的一个参数一个是过期时间，一个是定时续约过期时间

通过阅读源码知道lesstime参数决定是否续约

    private <T> RFuture<Long> tryAcquireAsync(long leaseTime, TimeUnit unit, final long threadId) {
        if (leaseTime != -1L) {
            return (leaseTime, unit, threadId, RedisCommands.EVAL_LONG);
        } else {
            RFuture<Long> ttlRemainingFuture = (().getCfg().getLockWatchdogTimeout(), , threadId, RedisCommands.EVAL_LONG);
            (new FutureListener<Long>() {
                public void operationComplete(Future<Long> future) throws Exception {
                    if (()) {
                        Long ttlRemaining = (Long)();
                        if (ttlRemaining == null) {
                            (threadId);
                        }

                    }
                }
            });
            return ttlRemainingFuture;
        }
    }

总结一点

if(leaseTime==-1L){
    开启自动续期的定时任务，不断重置过期时间为lockWatchdogTimeout
    定时任务的频率为lockWatchdogTimeout配置时间的1/3
}else{
    不自动续期
    设置过期时间为leaseTime
}

所有属性介绍 /articles/551640/

其他锁类型的锁参考
(联锁，红锁，读写锁,信号量,可过期性信号量)
/l1028386804/article/details/73523810

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