January 2018
Beginner to intermediate
234 pages
7h 8m
Chinese
Content preview from Kafka权威指南
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初识
Kafka
｜
7
生产者
Broker1
Broker2
主题A
的分区0
主题A
的分区1
主题A
的分区1
首领
首领
消息A/0 来自A/0的消息
来自A/1的消息
消息A/1
复制A/0 复制A/1
主题A
的分区0
消费者
Kafka集群
图 1-7：集群里的分区复制
保留消息
（在一定期限内）是
Kafka
的一个重要特性。
Kafka broker
默认的消息保留策略
是这样的：要么保留一段时间（比如
7
天），要么保留到消息达到一定大小的字节数（比
如
1GB
）。当消息数量达到这些上限时，旧消息就会过期并被删除，所以在任何时刻，可
用消息的总量都不会超过配置参数所指定的大小。主题可以配置自己的保留策略，可以将
消息保留到不再使用它们为止。例如，用于跟踪用户活动的数据可能需要保留几天，而应
用程序的度量指标可能只需要保留几个小时。可以通过配置把主题当作
紧凑型日志
，只有
最后一个带有特定键的消息会被保留下来。这种情况对于变更日志类型的数据来说比较适
用，因为人们只关心最后时刻发生的那个变更。
1.2.6
多集群
随着
Kafka
部署数量的增加，基于以下几点原因，最好使用多个集群。
•
数据类型分离
•
安全需求隔离
•
多数据中心（灾难恢复）
如果使用多个数据中心，就需要在它们之间复制消息。这样，在线应用程序才可以访问到
多个站点的用户活动信息。例如，如果一个用户修改了他们的资料信息，不管从哪个数据
中心都应该能看到这些改动。或者多个站点的监控数据可以被聚集到一个部署了分析程序
和告警系统的中心位置。不过，
Kafka
的消息复制机制只能在单个集群里进行，不能在多 ...
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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.