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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通信和数据契约
｜
33
3.1.3
全能的
schema
演化
schema
格式必须支持一整套
schema
演化规则。
schema
演化使生产者能够更新其服务的输
出格式，同时允许消费者继续不间断地消费事件。业务变更可能需要添加新字段、弃用旧
字段或扩展字段范围。
schema
演化框架确保这些变更可以安全地发生
，并且生产者和消费
者可以相互独立地更新。
如果没有
schema
演化的支持
，那么服务更新可能会有很高的代价。生产者和消费者被迫
密切协调，以前兼容的旧数据可能不再与当前系统兼容。当生产者更改数据
schema
时，
期望消费者更新他们的服务是不合理的。事实上，微服务的核心价值主张是，除非在特殊
情况下，否则它们应该独立于其他服务的发布周期。
一组显式的
schema
演化规则可以让消费者和生产者按照自己的时间安排更新应用程序
。
这些规则称为
兼容性类型
。
向前兼容性
允许像读取旧
schema
生成的数据一样读取新
schema
生成的数据
。在事件驱动架构中，
这是一个特别有用的演化需求，因为最常见的系统变更模式是从生产者用新的
schema
更新其数据定义并生成数据开始的。消费者只需要在访问新字段时更新其
schema
副本
和代码。
向后兼容性
允许像读取新
schema
生成的数据一样读取旧
schema
生成的数据
。这使得数据消费者可
以用新的
schema
读取旧的数据。向后兼容性对于以下场景来说特别有用。
•
消费者正在等待上游团队发布新特性。如果新的
schema
已被定义
，那么消费者就
可以在生产者发布之前发布自己的更新。
• schema
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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.