May 2024
Intermediate
278 pages
5h 24m
Chinese
Content preview from 构建可扩展分布式系统：方法与实践
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可扩展的事件驱动处理
｜
239
•
你可以修改现有的事件处理逻辑，以添加新功能或修复错误。然后，你可以在完整
的日志上执行新逻辑以丰富结果或修复错误。
•
如果发生服务器或磁盘故障，你可以从日志中恢复最后已知的状态并重播事件以恢
复数据集。这类似于事务日志在数据库系统中的作用。
消费者
图 14-2：使用事件日志实现跨微服务复制状态变更
与所有事情一样，不可变的、仅允许追加的日志也有缺点。我在下面的边栏中简要描述
其中之一
—
删除事件，以及
Apache Kafka
的相关功能。你可以阅读更多关于设计事件
驱动架构和模式的内容（例如事件协作和事件溯源）。我将在
14.3
节为你介绍几个优秀
的资源。然而，在本章的剩余部分，我想探索
Apache Kafka
平台的特性。
从日志中删除事件
有一些用例需要删除日志条目。一个著名的用例是欧盟《通用数据保护条例》（GDPR）
法律的“被遗忘权”监管要求。仅允许追加的不可变日志不是为删除条目而设计的，
可能会使删除条目出现问题。
Apache Kafka 提供了两种主要的日志条目删除机制：
生存时间
在默认的两周后删除日志条目。你可以调整它来满足你对日志条目保留和删除
的要求。
压缩主题
主题可以配置为仅保留给定事件键的最新条目。如果需要删除现有的日志条目，
你只需写入一个具有相同键和空值的新条目。然后，Kafka 会将较旧的条目标记
为删除。事件实际上在压缩主题中被标记为删除，并在稍后某个时间段（日志
压缩任务运行时）被删除。同样，此任务的频率是可配置的。
14.2 Apache Kafka ...
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I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.