November 2022
Beginner to intermediate
346 pages
11h
Chinese
Content preview from Kafka权威指南（第2版）
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深入
Kafka
｜
115
为分区和副本选好合适的
broker
之后，接下来要决定新分区应该被放在哪个目录。我们会
为每个分区分配目录，规则很简单：计算每个目录里的分区数量，新分区总是会被放在分
区数量最少的那个目录。也就是说，如果添加了一个新磁盘，那么所有新分区都会被放到
这个磁盘。这是因为在达到均衡分配的状态之前，新磁盘的分区数量总是最少的。
注意磁盘空间
需要注意的是，在将分区分配给
broker
时，我们不会考虑可用空间和工作负
载，而在将分区分配给磁盘时会考虑分区数量，但不考虑分区大小。如果有
些
broker
的磁盘空间比其他
broker
大（有可能是因为集群同时使用了旧服务
器和新服务器）、有些分区特别大，或者同一个
broker
上有大小不同的磁盘，
那么在分配分区时就要小心一些。
6.5.3
文件管理
数据保留是
Kafka
的一个重要概念。
Kafka
不会一直保留数据，也不会一直等到消息被所
有消费者读取了之后才将其删除。相反，
Kafka
管理员会为每个主题配置数据保留期限
，
主题的数据要么在达到指定的时间之后被清除，要么在达到指定的数量之后被清除。
在一个大文件中查找和删除消息既费时又很容易出错，所以我们会把分区分成若干个
片
段
。在默认情况下，每个片段包含
1 GB
或一周的数据
，以较小的那个为准。在
broker
向
分区写入数据时，如果触及任意一个上限，就关闭当前文件，并打开一个新文件。
当前正在写入数据的片段叫作
活动片段
。活动片段永远不会被删除，所以，如果你配置的
保留时间是
1
天
，但片段里包含了
5
天的数据，那么这些数据就会被保留 ...
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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.