秒杀系统优化：Redis+MQ实战方案

黑马点评秒杀优化方案

Redis预减库存与异步下单
秒杀开始前将商品库存加载到Redis，用户请求到达时先执行Redis库存预减，避免频繁访问数据库。预减成功后生成异步下单任务，通过消息队列（如RabbitMQ）削峰填谷，保证系统稳定性。

分布式锁防超卖
使用Redis的SETNX命令或Redisson实现分布式锁，确保库存扣减和订单创建的原子性。锁粒度细化到商品ID级别，避免全局锁的性能瓶颈。

缓存热点数据
采用多级缓存策略：Nginx本地缓存+Redis集群缓存+JVM缓存。针对热点商品使用Redis Cluster分片存储，配合HASH TAG保证同一商品数据落在同一节点。

限流与降级

网关层限流：通过Sentinel或Nginx限制QPS
接口层限流：使用Guava RateLimiter
降级策略：当库存不足时直接返回静态页面，减少后端压力

场景补充设计

秒杀结果轮询
前端提交请求后通过/result接口轮询结果，后端采用Redis存储订单状态（key为userID:goodsID），避免频繁查询数据库。

库存预热与分段扣减
活动前通过定时任务将库存分段加载到Redis（如分10段），扣减时随机选择段位，减少单个Key的竞争压力。

数据一致性保障

最终一致性：通过MQ重试机制确保异步下单成功
对账补偿：定时任务核对Redis与数据库库存差异
事务消息：RocketMQ事务消息保证本地事务与消息发送的原子性

性能压测指标

基准数据建议

单机TPS：≥2000（4核8G配置）
Redis集群：≥5万QPS
消息处理延迟：<500ms
订单创建耗时：<100ms（异步场景）

监控维度

Redis集群CPU/内存/网络IO
MQ积压情况监控
服务接口TP99响应时间
数据库慢查询日志分析

代码示例（关键逻辑）

Redis库存预减

public boolean seckillPreReduce(Long goodsId) {
    String key = "seckill:stock:" + goodsId;
    Long remain = redisTemplate.opsForValue().decrement(key);
    if (remain < 0) {
        redisTemplate.opsForValue().increment(key); // 回滚
        return false;
    }
    return true;
}

分布式锁实现

public boolean createOrder(Long userId, Long goodsId) {
    String lockKey = "seckill:lock:" + goodsId;
    RLock lock = redissonClient.getLock(lockKey);
    try {
        if (lock.tryLock(1, 10, TimeUnit.SECONDS)) {
            // 执行库存扣减与订单创建
        }
    } finally {
        lock.unlock();
    }
}

消息队列消费

@RabbitListener(queues = "seckill.queue")
public void processOrder(SeckillMessage message) {
    // 异步处理订单创建
    orderService.createAsyncOrder(message);
}

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