redisson 分布式锁实现

墨蓝 2023-09-29 13:30 20阅读 0赞

## redisson ##

建议阅读时间: 2min

redisson 实现分布式锁的机制如下：

![96402f9c79825358efcb8220ac1f5b1d.png][]

依赖版本

implementation 'org.redisson:redisson-spring-boot-starter:3.17.0'

## 测试代码 ##

下面是模拟一个商品秒杀的场景，示例代码如下：

public class RedissonTest {
    
        public static void main(String[] args) {
            //1. 配置部分
            Config config = new Config();
            String address = "redis://127.0.0.1:6379";
            SingleServerConfig serverConfig = config.useSingleServer();
            serverConfig.setAddress(address);
            serverConfig.setDatabase(0);
            config.setLockWatchdogTimeout(5000);
            Redisson redisson = (Redisson) Redisson.create(config);
    
    
            RLock rLock = redisson.getLock("goods:1000:1");
            //2. 加锁
            rLock.lock();
            try {
                System.out.println("todo 逻辑处理 1000000.");
            } finally {
                if (rLock.isLocked() && rLock.isHeldByCurrentThread()) {
                    //3. 解锁
                    rLock.unlock();
                }
            }
    
        }
    }

## 加锁设计 ##

rLock.lock();是加锁的核心代码，我们一起来看看调用栈

![6231207adbe6fdcbe6a302a5ee3e7b4a.png][]

加锁的核心方法是：org.redisson.RedissonLock\#tryLockInnerAsync

<T> RFuture<T> tryLockInnerAsync(long waitTime, long leaseTime, TimeUnit unit, long threadId, RedisStrictCommand<T> command) {
            return evalWriteAsync(getRawName(), LongCodec.INSTANCE, command,
                    "if (redis.call('exists', KEYS[1]) == 0) then " +
                            "redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
                            "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                            "return nil; " +
                            "end; " +
                            "if (redis.call('hexists', KEYS[1], ARGV[2]) == 1) then " +
                            "redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
                            "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                            "

[96402f9c79825358efcb8220ac1f5b1d.png]: https://img-blog.csdnimg.cn/img_convert/96402f9c79825358efcb8220ac1f5b1d.png
[6231207adbe6fdcbe6a302a5ee3e7b4a.png]: https://img-blog.csdnimg.cn/img_convert/6231207adbe6fdcbe6a302a5ee3e7b4a.png