-- 危險(xiǎn)的更新語(yǔ)句
UPDATE product SET stock = stock -1 
WHERE id=123 AND stock>0;

UPDATE product 
SET stock = stock -1, version=version+1 
WHERE id=123 AND version=#{currentVersion};

@Transactional
public boolean deductStock(Long productId) {
    Product product = productDao.selectForUpdate(productId);
    if (product.getStock() <= 0) return false;
    
    int affected = productDao.updateWithVersion(
        productId, 
        product.getVersion(),
        product.getStock()-1
    );
    return affected > 0;
}

// Lua腳本保證原子性
String lua = "if redis.call('get', KEYS >= ARGV[1] then " +
             "return redis.call('decrby', KEYS[1], ARGV " +
             "else return -1 end";

public boolean preDeduct(String itemId, int count) {
    RedisScript<Long> script = new DefaultRedisScript<>(lua, Long.class);
    Long result = redisTemplate.execute(script, 
        Collections.singletonList(itemId), count);
    return result != null && result >= 0;
}

RLock lock = redisson.getLock("stock_lock:"+productId);
try {
    if (lock.tryLock(1, 10, TimeUnit.SECONDS)) {
        // 執(zhí)行庫(kù)存操作
    }
} finally {
    lock.unlock();
}

// RocketMQ事務(wù)消息示例
TransactionMQProducer producer = new TransactionMQProducer("stock_group");
producer.setExecutor(new TransactionListener() {
    @Override
    public LocalTransactionState executeLocalTransaction(Message msg) {
        // 扣減數(shù)據(jù)庫(kù)庫(kù)存
        return LocalTransactionState.COMMIT_MESSAGE;
    }
});

// Guava RateLimiter限流
RateLimiter limiter = RateLimiter.create(1000); // 每秒1000個(gè)令牌

public boolean preDeduct(Long itemId) {
    if (!limiter.tryAcquire()) return false;
    
    // 寫(xiě)入預(yù)扣庫(kù)存表
    preStockDao.insert(itemId, userId);
    return true;
}

// 錯(cuò)誤示例：先刪緩存再寫(xiě)庫(kù)
redisTemplate.delete("stock:"+productId);
productDao.updateStock(productId, newStock); // 存在并發(fā)寫(xiě)入窗口

@Transactional
public void cancelOrder(Order order) {
    stockDao.restock(order.getItemId(), order.getCount());
    orderDao.delete(order.getId());
}

// 錯(cuò)誤示例：全局限鎖
RLock globalLock = redisson.getLock("global_stock_lock");