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Apache-2.0

SeckillProject

项目简介:

​ SeckillProject基于Springboot开发的秒杀系统,实现的功能主要是登录、商品列表、商品详情、秒杀商品,订单详情等功能。在系统业务处理中,使用到分布式session维持会话、Redis预减库存降低数据库访问压力,消息队列异步下单(削峰)、客户端轮询结果、接口限流防刷等

开发技术:

后端处理:SpringBoot 、MyBatis 、 MySQL、JSR303、RabbitMQ、Redis、Druid

前端处理:Html、jQuery 、Thymeleaf

实现细节记录:

1、用户密码两次MD5加密

第一次MD5加密:防止用户明文密码在网络进行传输

第二次MD5加密:防止数据库被盗,避免通过MD5反推出密码,双重保险

2、分布式session维持会话

后端通过验证用户账号密码都正确情况下,通过UUID生成唯一id作为token,再将token作为key、用户信息对象作为value存储到redis,同时将token存储到cookie,维持会话状态。当用户访问接口时,只需从cookie取出对应的token信息,根据token键值从redis获取用户对象。

3、异常统一处理

通过自定义拦截器的方式,对所有所有异常进行拦截,并进行相应的处理,然后把结果信息返回给客户端处理。

4、页面缓存 + 对象缓存

页面缓存:

​ 通过在手动渲染得到的html页面缓存到redis,下次访问相同页面时直接从redis中获取进行返回,减少服务端处理的压力

对象缓存:

​ 把相应的热点对象进行缓存到Redis,比如:用户对象、商品对象、订单对象等,利用缓存来减少对数据库的访问,提高系统的响应速度。

5、页面静态化

​ 使用前后端分离技术,用ajax实现异步请求数据,得到数据后绑定到当前页面。第一次访问后,页面和数据都会缓存到客户端的浏览器,当再次请求相同的页面时会直接从浏览器缓存加载。

6、内存标记 + redis预减库存 + RabbitMQ异步处理

​ 通过内存标记 + redis预减库存 + RabbitMQ异步处理下单,最后才会访问数据库,减少对数据库的访问,是系统整体负载达到最高。

具体实现:

//系统启动时会对其初始化,将所有秒杀商品id存入map,库存为0是为true
private Map<Long,Boolean> localOverMap = new HashMap<Long,Boolean>();

//内存标记,减少redis访问
boolean over = localOverMap.get(goodsId);
if(over) {
    return Result.error(CodeMsg.MIAO_SHA_OVER);
}
//redis预减库存
long stock = redisService.decr(GoodsKey.getSeckillGoodsStock, "" + goodsId);//10
if (stock < 0) {
    localOverMap.put(goodsId,true);
    return Result.error(CodeMsg.MIAO_SHA_OVER);
}

//判断是否已经秒杀到了
SeckillOrder order = orderService.getOrderByUserIdGoodsId(user.getId(), goodsId);
if(order != null) {
    return Result.error(CodeMsg.REPEATE_MIAOSHA);
}

//压入消息队列
//入队
SeckillMessage sm = new SeckillMessage();
sm.setUser(user);
sm.setGoodsId(goodsId);
sender.sendSeckillMessage(sm);
  1. 在用户发起秒杀访问时,先访问本地已经初始化好的map,看当前秒杀商品id的库存是否已售罄,若已售罄,直接返回秒杀结束异常,若库存还有,在执行下面的操作。通过内存标记可以减少对后面步骤中的redis访问操作,降低redis的压力,不然每个请求都将访问一次redis

  2. 系统启动时,即将商品和库存数据初始化到redis中,所有的抢购操作都在redis中进行处理,通过Redis预减少库存来减少数据库访问

  3. 通过使用RabbitMQ用异步队列处理下单,实现系统高响应。此处响应客户端后,一般都是抢购成功了,当然不排除例外,此时客户端通过ajax请求轮询访问下单结果接口,直到响应状态成功或者失败

7、解决超卖

​ 一开始没有优化时,通过Jmeter压测发现,数据库商品出现了负数的情况,并且产生的订单数量也是超过了当时库存数量的。简而言之,就是库存为10,一万个线程压测后,库存变成负值(-5,-13,-35都可能出现)。

解决方法:

  1. 更sql语句,只有当库存大于0才能更新库存

    update seckill_goods set stock_count = stock_count-1 where goods_id = #{goodsId} and stock_count > 0
  2. 对用户id和商品id建立一个唯一索引,通过这种约束避免同一用户发同时两个请求秒杀到两件相同商品

image-20200604000433842

  1. 实现乐观锁,给商品信息表增加一个version字段,为每一条数据加上版本。每次更新的时候version+1,并且更新时候带上版本号,当提交前版本号等于更新前版本号,说明此时没有被其他线程影响到,正常更新,如果冲突了则不会进行提交更新。当库存是足够的情况下发生乐观锁冲突就进行一定次数的重试。

8、接口限流

​ 通过记录用户在某一时间内访问的次数进行拒绝。

效果展示

1、项目结构

image-20200604001323172

2、登录页

image-20200604001403938

3、商品列表

image-20200604001511474

4、商品详情

image-20200604001859333

5、订单详情

image-20200604001921870

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简介

基于SpringBoot+RabbitMQ+Redis开发的秒杀系统(异步下单、热点数据缓存、解决超卖) 展开 收起
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