January 2018
Beginner to intermediate
234 pages
7h 8m
Chinese
Content preview from Kafka权威指南
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52
｜
第
4
章
参数，以及如何根据实际需要来配置这些参数。
心跳行为在最近版本中的变化
在
0.10.1
版本里，
Kafka
社区引入了一个独立的心跳线程，可以在轮询消息的空档发
送心跳。这样一来，发送心跳的频率（也就是消费者群组用于检测发生崩溃的消费者
或不再发送心跳的消费者的时间）与消息轮询的频率（由处理消息所花费的时间来确
定）之间就是相互独立的。在新版本的
Kafka
里，可以指定消费者在离开群组并触发
再均衡之前可以有多长时间不进行消息轮询，这样可以避免出现
活锁（
livelock
）， 比
如有时候应用程序并没有崩溃，只是由于某些原因导致无法正常运行。这个配置与
session.timeout.ms
是相互独立的，后者用于控制检测消费者发生崩溃的时间和停止
发送心跳的时间。
本章的剩余部分将会讨论使用旧版本
Kafka
会面临的一些问题，以及如何解决这些问
题。本章还包括如何应对需要较长时间来处理消息的情况的讨论，这些与
0.10.1
或更
高版本的
Kafka
没有太大关系。如果你使用的是较新版本的
Kafka
，并且需要处理耗
费较长时间的消息，只需要加大
max.poll.interval.ms
的值来增加轮询间隔的时长。
分配分区是怎样的一个过程
当消费者要加入群组时，它会向群组协调器发送一个
JoinGroup
请求。第一
个加入群组的消费者将成为“群主”。群主从协调器那里获得群组的成员列
表（列表中包含了所有最近发送过心跳的消费者，它们被认为是活跃的），
并负责给每一个消费者分配分区。它使用一个实现了
PartitionAssignor ...
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