高并发后端架构设计：从流量削峰、链路解耦到数据一致性的落地实践

package middleware

import (
    "net/http"
    "golang.org/x/time/rate"
)

// 每秒生成 2000 个令牌，桶容量 5000
var limiter = rate.NewLimiter(2000, 5000)

func RateLimitMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        if !limiter.Allow() {
            // 快速失败，不要让请求挂起消耗 Goroutine
            http.Error(w, `{"code": 429, "msg": "Too Many Requests"}`, http.StatusTooManyRequests)
            return
        }
        next.ServeHTTP(w, r)
    })
}

UPDATE tb_inventory SET stock = stock - 1 WHERE sku_id = 1001 AND stock > 0;

-- KEYS[1]: 缓存中库存的 key (如: item:stock:1001)
-- ARGV[1]: 扣减数量 (如: 1)
local stock = redis.call('get', KEYS[1])
if not stock then
    return -1 -- 缓存未预热
end

local stockNum = tonumber(stock)
local deductNum = tonumber(ARGV[1])

if stockNum < deductNum then
    return 0 -- 库存不足
end

redis.call('decrby', KEYS[1], deductNum)
return 1 -- 扣减成功

                    +--------------------+
                    |    Client Request  |
                    +---------+----------+
                              |
                              v
                    +--------------------+
                    |  API / Order Svc   |
                    +---------+----------+
                              |
                 +------------+------------+
                 | (1. 写本地事务)         | (2. 投递事务消息)
                 v                         v
       +------------------+      +-------------------+
       | MySQL (分库分表)  |      |     RocketMQ      |
       | 状态: PAYING     |      +---------+---------+
       +------------------+                |
                                           v (3. 异步订阅)
                                 +-------------------+
                                 |  Accounting Svc   |
                                 | (记账/积分/通知)  |
                                 +-------------------+

// Java 示例：对非核心下游使用独立线程池隔离
@Configuration
public class ThreadPoolConfig {

    @Bean("orderNoticeExecutor")
    public ThreadPoolExecutor orderNoticeExecutor() {
        return new ThreadPoolExecutor(
            10, 
            20, 
            60L, 
            TimeUnit.SECONDS,
            new ArrayBlockingQueue<>(500), // 必须是有界队列
            new ThreadFactoryBuilder().setNameFormat("order-notice-%d").build(),
            new ThreadPoolExecutor.DiscardOldestPolicy() // 明确拒绝策略
        );
    }
}