欢迎关注微信公众号：石杉的架构笔记（id：shishan100）面试

个人新课**《C2C 电商系统微服务架构120天实战训练营》在公众号儒猿技术窝**上线了，感兴趣的同窗，能够点击下方连接了解详情：算法

1、前情回顾

以前给你们聊了一下，面试时若是遇到消息中间件这个话题，面试官上来可能问的两个问题：服务器

大家的系统架构中为何要引入消息中间件？
系统架构中引入消息中间件有什么缺点？

关于这两个问题的回答，能够参见以前的两篇文章：微信

在问完这两个问题以后，不一样风格的面试官可能会展开不一样的发问。markdown

针对那种工做年限比较长的资深的同窗，可能会开始就候选人所在公司使用的消息中间件，深刻里面的技术细节，好比让你聊聊RocketMQ的架构原理和核心源码？网络

可是另一种面试风格，会先从大家的项目和业务入手进行考察，好比像下面这样：架构

消息中间件在大家生产项目里具体是哪一个业务场景下落地的？
这个业务场景有什么技术挑战？
为何必需要在这个业务场景里用消息中间件技术？
具体使用消息中间件的时候是怎么来用的？

好！这篇文章，我们从第二种风格来聊聊。并发

2、业务场景介绍

咱们会落地到某个具体业务系统的某个场景下，看看如何使用消息中间件，而后其效果是什么。app

业务场景的话，我们就用你们都很熟悉的电商业务为例，这里为了便于理解，对其作了必定的抽象和简化。

你们仍是来考虑一个下订单的业务流程，好比你下个订单，此时须要干几件事情：

更新订单状态为“待发货”（耗时20ms）
扣减商品库存（耗时100ms）
增长会员积分（耗时80ms）
附赠优惠券（耗时50ms）
仓储调度发货（耗时几十秒）。

说明一下：上述环节，为了便于你们理解，作了简化。实际真正复杂的电商系统里，总体环节和业务流程会比这个复杂不少倍，并且耗时也绝对不是上面那么简单的。

老规矩！咱们仍是经过一张手绘图，来看看这整个的业务流程：

如上图，这个下订单的业务流程中：

更新订单状态（20ms） + 扣减商品库存（100ms） + 增长会员积分（80ms） + 附赠优惠券（50ms） = 250ms。

也就是说，仅仅是这4个流程的话，也就200多毫秒的耗时。

200多毫秒的耗时，对用户下单体验来讲是很是快速的，几乎就是一瞬间就完成了，不会感到过多的停顿，也就是一会儿就能够看到本身下单成功了。

可是，若是加上那个调度仓储发货呢？

那个环节须要读取大量的数据、使用多仓库/多货位的调度算法、还要跟C/S架构的仓储系统进行网络通讯，所以咱们这里假设这个环节可能会耗时数十秒。

一旦加上那个调度仓储发货的环节到这个下单流程里，就可能致使用户要等页面卡顿几十秒后才会看到下单成功的提示，这个用户体验就至关的差了。

按照以前一篇文章「Java进阶面试系列之一」大家系统架构中为什么要引入消息中间件？的说法。对于这种场景，彻底适合使用消息中间件来进行异步化调用。

也就是说，订单服务对仓储调度发货，仅仅是发送一个消息到MQ里，而后仓储服务消费消息以后再慢慢的执行调度算法，而后分配商品发货任务给对应的仓库便可。

这样的话，就能够把耗时几十秒的仓储调度发货的环节，从下单流程里摘除出去了。进而保证下单流程就仅仅是耗时200多毫秒而已。

至于那个耗时几十秒的仓储调度发货环节，咱们经过异步的方式慢慢执行便可，不会影响用户下单的体验。

以上过程，咱们一样来一张图，你们直观的感觉一下：

3、初步落地

好！接下来咱们就假设你们在实际生产中还没用过消息中间件，我们从0开始，看看如何落地？

对于已经在生产中使用过消息中间件的小伙伴，不妨也看看，权当复习，温故知新！

咱们以RabbitMQ为例，假如你用的消息中间件是RabbitMQ，那么咱们对这个消息中间件应该如何安装和部署呢？

很简单，RabbitMQ的官方文档里提供了很是详细的安装部署步骤，你能够在本身的笔记本电脑本地安装，也能够在公司的服务器上部署。

如今假设你已经参考了官方文档并安装完成，那么接下来在代码层面应该怎么来引入RabbitMQ以及在系统里实现收发消息呢？

下面经过一些HelloWorld级别的代码和一些简单的示例图，给你们演示一下RabbitMQ是如何收发消息的。

对于不少在实际生产中使用过MQ的同窗，这些代码可能对实际生产中使用过MQ的同窗，显得太简单了。

不过考虑到不少初学者可能连用都没有用过MQ，甚至是才据说消息中间件不久，因此笔者认为这些demo代码以及手工绘图，仍是颇有必要。

好！看完了代码，这个时候，咱们能够经过一张图来想象一下两个服务之间的通讯。

订单服务你能够启动多个，不一样的订单服务均可以往一个RabbitMQ的queue里推送消息。

仓储服务你也能够启动多个，多个仓储服务会采用round-robin的轮询算法，每一个服务实例均可以从RabbitMQ queue里消费到一部分的消息。

上面的图里，订单服务在MQ专业术语中叫作**“生产者”**，英文是“Producer”，意思就是这个服务是专门负责生产消息投递到MQ的。

仓储服务在MQ专业术语中叫作**“消费者”**，英文是“Consumer”，意思就是这个服务专门是负责从MQ消费消息而后处理的。

这个时候，这套异步通讯的架构就能够跑起来了。

好了，到目前为止，虽然这个代码还存在很多问题，可是不要紧，大致上咱们已经给一些不太熟悉MQ技术的同窗，从一个比较形象易于理解简化后的电商业务场景出发，经过HelloWorld级别的示例代码和手工绘图，将MQ这个技术落地跑起来了。

更进一步，各位同窗彻底能够参照这个文章里的案例，思考一下：本身负责的项目里，有没有相似的业务场景可使用MQ的？

而后想办法在本身的项目里落地使用MQ的技术来作一下异步化，提高核心流程的性能。

这样将来在跳槽面试的时候，才能够作到游刃有余，有本身的一套东西能够说。

END

【Java进阶面试系列之四】哥们，若是消息中间件的消费者宕机了，会怎么样？【敬请期待】

若有收获，请帮忙转发，您的鼓励是做者最大的动力，谢谢！

一大波微服务、分布式、高并发、高可用的原创系列文章正在路上

欢迎扫描下方二维码，持续关注：

石杉的架构笔记（id:shishan100）

十余年BAT架构经验倾囊相授

**> **推荐阅读：** > > 一、[拜托！面试请不要再问我Spring Cloud底层原理](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Flink.juejin.im%2525252525252F%2525252525253Ftarget%2525252525253Dhttps%252525252525253A%252525252525252F%252525252525252Flink.juejin.im%252525252525252F%252525252525253Ftarget%252525252525253Dhttps%25252525252525253A%25252525252525252F%25252525252525252Fjuejin.im%25252525252525252Fpost%25252525252525252F5be13b83f265da6116393fc7) > > 二、[【双11狂欢的背后】微服务注册中心如何承载大型系统的千万级访问？](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Flink.juejin.im%2525252525252F%2525252525253Ftarget%2525252525253Dhttps%252525252525253A%252525252525252F%252525252525252Flink.juejin.im%252525252525252F%252525252525253Ftarget%252525252525253Dhttps%25252525252525253A%25252525252525252F%25252525252525252Fjuejin.im%25252525252525252Fpost%25252525252525252F5be3f8dcf265da613a5382ca) > > 三、[【性能优化之道】每秒上万并发下的Spring Cloud参数优化实战](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Flink.juejin.im%2525252525252F%2525252525253Ftarget%2525252525253Dhttps%252525252525253A%252525252525252F%252525252525252Flink.juejin.im%252525252525252F%252525252525253Ftarget%252525252525253Dhttps%25252525252525253A%25252525252525252F%25252525252525252Fjuejin.im%25252525252525252Fpost%25252525252525252F5be83e166fb9a049a7115580) > > 四、[微服务架构如何保障双11狂欢下的99.99%高可用](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Flink.juejin.im%2525252525252F%2525252525253Ftarget%2525252525253Dhttps%252525252525253A%252525252525252F%252525252525252Flink.juejin.im%252525252525252F%252525252525253Ftarget%252525252525253Dhttps%25252525252525253A%25252525252525252F%25252525252525252Fjuejin.im%25252525252525252Fpost%25252525252525252F5be99a68e51d4511a8090440) > > 五、[兄弟，用大白话告诉你小白都能听懂的Hadoop架构原理](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Flink.juejin.im%2525252525252F%2525252525253Ftarget%2525252525253Dhttps%252525252525253A%252525252525252F%252525252525252Flink.juejin.im%252525252525252F%252525252525253Ftarget%252525252525253Dhttps%25252525252525253A%25252525252525252F%25252525252525252Fjuejin.im%25252525252525252Fpost%25252525252525252F5beaf02ce51d457e90196069) > > 六、[大规模集群下Hadoop NameNode如何承载每秒上千次的高并发访问](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Flink.juejin.im%2525252525252F%2525252525253Ftarget%2525252525253Dhttps%252525252525253A%252525252525252F%252525252525252Flink.juejin.im%252525252525252F%252525252525253Ftarget%252525252525253Dhttps%25252525252525253A%25252525252525252F%25252525252525252Fjuejin.im%25252525252525252Fpost%25252525252525252F5bec278c5188253e64332c76) > > 七、【[性能优化的秘密】Hadoop如何将TB级大文件的上传性能优化上百倍](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Flink.juejin.im%2525252525252F%2525252525253Ftarget%2525252525253Dhttps%252525252525253A%252525252525252F%252525252525252Flink.juejin.im%252525252525252F%252525252525253Ftarget%252525252525253Dhttps%25252525252525253A%25252525252525252F%25252525252525252Fjuejin.im%25252525252525252Fpost%25252525252525252F5bed82a9e51d450f9461cfc7) > > [八、](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Fjuejin.im%2525252525252Fpost%2525252525252F5bf2c6b6e51d456693549af4)[拜托，面试请不要再问我TCC分布式事务的实现原理坑爹呀！](https://juejin.cn/post/6844903716089233416) [](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Fjuejin.im%2525252525252Fpost%2525252525252F5bf2c6b6e51d456693549af4) > > 九、[【坑爹呀！】最终一致性分布式事务如何保障实际生产中99.99%高可用？](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Fjuejin.im%2525252525252Fpost%2525252525252F5bf2c6b6e51d456693549af4) > > 十、[拜托，面试请不要再问我Redis分布式锁的实现原理！](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Fjuejin.im%2525252525252Fpost%2525252525252F5bf3f15851882526a643e207) > > **十一、****[【眼前一亮！】看Hadoop底层算法如何优雅的将大规模集群性能提高10倍以上？](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Flink.juejin.im%25252525253Ftarget%25252525253Dhttps%2525252525253A%2525252525252F%2525252525252Fjuejin.im%2525252525252Fpost%2525252525252F5bf5396f51882509a768067e)** > > **十二、****[亿级流量系统架构之如何支撑百亿级数据的存储与计算](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Flink.juejin.im%252525252F%252525253Ftarget%252525253Dhttps%25252525253A%25252525252F%25252525252Fjuejin.im%25252525252Fpost%25252525252F5bfab59fe51d4551584c7bcf)** > > 1三、[亿级流量系统架构之如何设计高容错分布式计算系统](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Flink.juejin.im%2525253Ftarget%2525253Dhttps%252525253A%252525252F%252525252Fjuejin.im%252525252Fpost%252525252F5bfbeeb9f265da61407e9679) > > 1四、[亿级流量系统架构之如何设计承载百亿流量的高性能架构](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Flink.juejin.im%25253Ftarget%25253Dhttps%2525253A%2525252F%2525252Fjuejin.im%2525252Fpost%2525252F5bfd2df1e51d4574b133dd3a) > > 1五、[亿级流量系统架构之如何设计每秒十万查询的高并发架构](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Flink.juejin.im%252F%253Ftarget%253Dhttps%25253A%25252F%25252Fjuejin.im%25252Fpost%25252F5bfe771251882509a7681b3a) > > 1六、[亿级流量系统架构之如何设计全链路99.99%高可用架构](https://link.juejin.im/?target=https%3A%2F%2Flink.juejin.im%3Ftarget%3Dhttps%253A%252F%252Fjuejin.im%252Fpost%252F5bffab686fb9a04a102f0022) > > 1七、[七张图完全讲清楚ZooKeeper分布式锁的实现原理](https://link.juejin.im/?target=https%3A%2F%2Fjuejin.im%2Fpost%2F5c01532ef265da61362232ed) > > 1八、[大白话聊聊Java并发面试问题之volatile究竟是什么？](https://juejin.cn/post/6844903730303746061) > > 1九、[大白话聊聊Java并发面试问题之Java 8如何优化CAS性能？](https://juejin.cn/post/6844903731234865160) > > 20、[大白话聊聊Java并发面试问题之谈谈你对AQS的理解？](https://juejin.cn/post/6844903732061159437) > > 2一、[大白话聊聊Java并发面试问题之公平锁与非公平锁是啥？](https://juejin.cn/post/6844903732883226637) > > 2二、[大白话聊聊Java并发面试问题之微服务注册中心的读写锁优化](https://juejin.cn/post/6844903734267510798) > > 2三、[互联网公司的面试官是如何360°无死角考察候选人的？（上篇）](https://juejin.cn/post/6844903734930046989) > > 2四、[互联网公司面试官是如何360°无死角考察候选人的？（下篇）](https://juejin.cn/post/6844903735655661581) > > 2五、[Java进阶面试系列之一：哥们，大家的系统架构中为何要引入消息中间件？](https://juejin.cn/post/6844903736444207117) > > 2六、[【Java进阶面试系列之二】：哥们，那你说说系统架构引入消息中间件有什么缺点？](https://juejin.cn/post/6844903737123667975) > > 2七、[【行走的Offer收割机】记一位朋友斩获BAT技术专家Offer的面试经历](https://juejin.cn/post/6844903741213130765)**

【Java进阶面试系列之三】哥们，消息中间件在大家项目里是如何落地的？【石杉的架构笔记】

1、前情回顾

2、业务场景介绍

3、初步落地