January 2018
Beginner to intermediate
234 pages
7h 8m
Chinese
Content preview from Kafka权威指南
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134
｜
第
8
章
•
fetch.min.bytes 和 fetch.max.wait。如果度量指标 fetch-rate 的值很高，说明消费者
发送的请求太多了，而且获取不到足够的数据。这个时候可以配置更大的 fetch.min.
bytes 和 fetch.max.wait，这样消费者的每个请求就可以获取到更多的数据，
broker
会
等到有足够多的可用数据时才将响应返回。
8.4
其他跨集群镜像方案
我们深入了解了
MirrorMaker
，因为
MirrorMaker
是
Kafka
的一部分。不过在实际使用当
中，
MirrorMaker
也存在一些不足。在
MirrorMaker
之外，还有其他的一些替代方案，它们
解决了
MirrorMaker
的局限性和复杂性问题。
8.4.1
优步的
uReplicator
优步在他们的
Kafka
集群上大规模地使用
MirrorMaker
，不过，随着主题和分区的增加以
及集群吞吐量的增长，他们开始面临一些问题。
再均衡延迟
MirrorMaker
中的消费者只是普通的消费者，在增加
MirrorMaker
的线程和实例、重启
MirrorMaker
实例或往白名单里添加新主题时，消费者都需要进行再均衡。正如在第
4
章
里所看到的那样，再均衡要求关闭所有的消费者，直到新的分区被分配给消费者。如果
主题和分区的数量很大，整个过程需要很长的时间。如果使用了旧版本的消费者则更是
如此，比如像优步那样。有时候，这会造成
5~10
分钟的不可用，导致镜像过程延后，堆
积大量的待镜像数据，需要更长的时间进行恢复，这将给其他消费者带来很大的延迟。 ...
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