Go与Redis实现分布式互斥锁和红锁

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

func (l *Lock) TryLock(ctx context.Context) error {
   success, err := l.client.SetNX(ctx, l.resource, l.randomValue, ttl).Result()
   if err != nil {
      return err
   }
   // 加锁失败
   if !success {
      return ErrLockFailed
   }
   // 加锁成功
   l.randomValue = randomValue
   return nil
}

func (l *Lock) Unlock(ctx context.Context) error {
   return l.script.Run(ctx, l.client, []string{l.resource}, l.randomValue).Err()
}

func (l *Lock) Lock(ctx context.Context) error {
	// 尝试加锁
	err := l.TryLock(ctx)
	if err == nil {
		return nil
	}
	if !errors.Is(err, ErrLockFailed) {
		return err
	}
	// 加锁失败，不断尝试
	ticker := time.NewTicker(l.tryLockInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			// 超时
			return ErrTimeout
		case <-ticker.C:
			// 重新尝试加锁
			err := l.TryLock(ctx)
			if err == nil {
				return nil
			}
			if !errors.Is(err, ErrLockFailed) {
				return err
			}
		}
	}
}

func (l *Lock) startWatchDog() {
	ticker := time.NewTicker(l.ttl / 3)
	defer ticker.Stop()
	for {
		select {
		case <-ticker.C:
			// 延长锁的过期时间
			ctx, cancel := context.WithTimeout(context.Background(), l.ttl/3*2)
			ok, err := l.client.Expire(ctx, l.resource, l.ttl).Result()
			cancel()
			// 异常或锁已经不存在则不再续期
			if err != nil || !ok {
				return
			}
		case <-l.watchDog:
			// 已经解锁
			return
		}
	}
}

func (l *Lock) TryLock(ctx context.Context) error {
	success, err := l.client.SetNX(ctx, l.resource, l.randomValue, l.ttl).Result()
	if err != nil {
		return err
	}
	// 加锁失败
	if !success {
		return ErrLockFailed
	}
	// 加锁成功，启动看门狗
	go l.startWatchDog()
	return nil
}

func (l *Lock) Unlock(ctx context.Context) error {
	err := l.script.Run(ctx, l.client, []string{l.resource}, l.randomValue).Err()
	// 关闭看门狗
	close(l.watchDog)
	return err
}

func (l *RedLock) TryLock(ctx context.Context) error {
	randomValue := gofakeit.UUID()
	var wg sync.WaitGroup
	wg.Add(len(l.clients))
	// 成功获得锁的Redis实例的客户端
	successClients := make(chan *redis.Client, len(l.clients))
	for _, client := range l.clients {
		go func(client *redis.Client) {
			defer wg.Done()
			success, err := client.SetNX(ctx, l.resource, randomValue, ttl).Result()
			if err != nil {
				return
			}
			// 加锁失败
			if !success {
				return
			}
			// 加锁成功，启动看门狗
			go l.startWatchDog()
			successClients <- client
		}(client)
	}
	// 等待所有获取锁操作完成
	wg.Wait()
	close(successClients)
	// 如果成功加锁得客户端少于客户端数量的一半+1，表示加锁失败
	if len(successClients) < len(l.clients)/2+1 {
		// 就算加锁失败，也要把已经获得的锁给释放掉
		for client := range successClients {
			go func(client *redis.Client) {
				ctx, cancel := context.WithTimeout(context.Background(), ttl)
				l.script.Run(ctx, client, []string{l.resource}, randomValue)
				cancel()
			}(client)
		}
		return ErrLockFailed
	}

	// 加锁成功，启动看门狗
	l.randomValue = randomValue
	l.successClients = nil
	for successClient := range successClients {
		l.successClients = append(l.successClients, successClient)
	}

	return nil
}

func (l *RedLock) startWatchDog() {
	l.watchDog = make(chan struct{})
	ticker := time.NewTicker(resetTTLInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ticker.C:
			// 延长锁的过期时间
			for _, client := range l.successClients {
				go func(client *redis.Client) {
					ctx, cancel := context.WithTimeout(context.Background(), ttl-resetTTLInterval)
					client.Expire(ctx, l.resource, ttl)
					cancel()
				}(client)
			}
		case <-l.watchDog:
			// 已经解锁
			return
		}
	}
}

func (l *RedLock) Unlock(ctx context.Context) error {
   for _, client := range l.successClients {
      go func(client *redis.Client) {
         l.script.Run(ctx, client, []string{l.resource}, l.randomValue)
      }(client)
   }
   // 关闭看门狗
   close(l.watchDog)
   return nil
}