Redis 分布式锁的正确实现：从 SETNX 到 Redisson 看门狗

// ❌ 非原子：setnx 成功但 expire 前宕机 → 死锁
if (redis.setnx("lock", "1") == 1) {
    redis.expire("lock", 30);
    // 业务
    redis.del("lock");
}

SET lock_key unique_value NX PX 30000

String result = jedis.set(key, requestId, "NX", "PX", 30000);
if ("OK".equals(result)) {
    try {
        // 业务逻辑
    } finally {
        // Lua 保证原子删除
        String script = "if redis.call('get', KEYS[1]) == ARGV[1] then " +
                        "return redis.call('del', KEYS[1]) else return 0 end";
        jedis.eval(script, Collections.singletonList(key),
                   Collections.singletonList(requestId));
    }
}

private void scheduleExpirationRenewal(String key) {
    Thread renewal = new Thread(() -> {
        while (!Thread.currentThread().isInterrupted()) {
            try {
                Thread.sleep(10000);  // 每 10s 续一次
                jedis.pexpire(key, 30000);
            } catch (InterruptedException e) {
                break;
            }
        }
    });
    renewal.setDaemon(true);
    renewal.start();
}

@Resource
private RedissonClient redisson;

public void seckill(Long productId) {
    RLock lock = redisson.getLock("seckill:" + productId);
    try {
        // 默认 30s，看门狗每 10s 自动续期
        boolean locked = lock.tryLock(10, 30, TimeUnit.SECONDS);
        if (!locked) {
            throw new BusinessException("系统繁忙，请重试");
        }
        // 扣库存
    } finally {
        lock.unlock();
    }
}