October 2021
Beginner to intermediate
250 pages
7h 11m
Chinese
Content preview from 微服务与事件驱动架构
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172
｜
第
13
章
13.4.1
实时请求内部状态存储
如图
13-4
所示，微服务可以提供来自其内部状态的结果。客户端请求被分发到一个负载均
衡器，这个负载均衡器会将请求路由到其中一个底层微服务实例。在这个例子中，只有一
个微服务实例，并且因为它物化了该应用程序的所有状态数据，所以在这个实例上可以获
得应用程序的所有数据。状态是通过消费两个输入事件流（
A
和
B
）进行物化的
，变更日
志备份在事件代理上。
客户端
负载均衡器
物化表P0
变更日志
事件流A
事件流B
处理拓扑
事件代理
实例0
1) 客户端发起请求
2) 负载均衡器分发请求
图 13-4：用 REST API 向客户端提供内容的 EDM 概览
现在的问题是，很多时候需要多个微服务实例来处理负载，并且实例之间有不同的内部状
态。当使用多个微服务实例时，必须将请求路由到它所需要的状态数据所在的正确实例
上，因为所有的内部状态都是根据键分片的，一个键只会对应一个分区。图
13-5
展示了客
户端发起请求，然后被路由到包含所需状态的正确实例的情况。
如果你的框架支持，那么状态存储的热副本（参见
7.3.4
节）也可以用于服
务直接调用的请求。请记住，热副本数据可能是过时的，过时程度与主状态
存储的复制延迟成比例。
集成事件驱动型和
“
请求
–
响应
”
型微服务
｜
173
客户端
负载均衡器
物化表 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.