如何设计一个秒杀系统，（高并发高可用分布式集群）

plaintext复制代码           +-----------+
           |  Client   |
           +-----------+
                |
                v
      +--------------------+
      |    Load Balancer   |
      +--------------------+
                |
                v
      +------------------------+
      |    API Gateway (Nginx) |
      +------------------------+
                |
                v
  +-------------+-------------+-------------+
  |             |             |             |
  v             v             v             v
+------+     +------+     +------+     +------+
| User |     | Prod |     | Order|     |Seckill|
| Svcs |     | Svcs |     | Svcs |     | Svcs |
+------+     +------+     +------+     +------+
  |             |             |             |
  v             v             v             v
+------+     +------+     +------+     +------+
|Cache |     |Cache |     |Cache |     |Cache |
|Redis |     |Redis |     |Redis |     |Redis |
+------+     +------+     +------+     +------+
  |             |             |             |
  v             v             v             v
+------+     +------+     +------+     +------+
| DB   |     | DB   |     | DB   |     | DB   |
+------+     +------+     +------+     +------+
  |             |             |             |
  v             v             v             v
+------+     +------+     +------+     +------+
| MQ   |     | MQ   |     | MQ   |     | MQ   |
+------+     +------+     +------+     +------+
  |
  v
+------+
| Moni |
| toring|
+------+

java复制代码@RestController
@RequestMapping("/seckill")
public class SeckillController {

    @Autowired
    private RedisTemplate<String, Object> redisTemplate;

    @Autowired
    private SeckillService seckillService;

    @RequestMapping(value = "/{productId}", method = RequestMethod.POST)
    public ResponseEntity<String> seckill(@PathVariable("productId") long productId) {
        // 1. 校验请求合法性（如验证码、用户身份等）

        // 2. 预扣减库存
        String stockKey = "seckill:stock:" + productId;
        Long stock = redisTemplate.opsForValue().decrement(stockKey);
        if (stock == null || stock < 0) {
            return ResponseEntity.status(HttpStatus.NOT_FOUND).body("Sold out");
        }

        // 3. 生成订单
        boolean result = seckillService.createOrder(productId);
        if (!result) {
            // 回退预扣减库存
            redisTemplate.opsForValue().increment(stockKey);
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Failed to create order");
        }

        return ResponseEntity.ok("Seckill success");
    }
}

@Service
public class SeckillService {

    @Autowired
    private OrderRepository orderRepository;

    @Transactional
    public boolean createOrder(long productId) {
        // 扣减数据库库存
        int updateCount = productRepository.decreaseStock(productId);
        if (updateCount <= 0) {
            return false;
        }

        // 创建订单
        Order order = new Order();
        order.setProductId(productId);
        order.setCreateTime(new Date());
        orderRepository.save(order);

        return true;
    }
}