January 2018
Beginner to intermediate
234 pages
7h 8m
Chinese
Content preview from Kafka权威指南
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82
｜
第
5
章
我们从分区首领开始，依次分配跟随者副本。如果分区
0
的首领在
broker 4
上，那么它的
第一个跟随者副本会在
broker 5
上，第二个跟随者副本会在
broker 0
上。分区
1
的首领在
broker 5
上，那么它的第一个跟随者副本在
broker 0
上，第二个跟随者副本在
broker 1
上。
如果配置了机架信息，那么就不是按照数字顺序来选择
broker
了，而是按照交替机架的方式
来选择
broker
。假设
broker 0
、
broker 1
和
broker 2
放置在同一个机架上，
broker 3
、
broker 4
和
broker 5
分别放置在其他不同的机架上。我们不是按照从
0
到
5
的顺序来选择
broker
，而
是按照
0
，
3
，
1
，
4
，
2
，
5
的顺序来选择，这样每个相邻的
broker
都在不同的机架上（如图
5-5
所示）。于是，如果分区
0
的首领在
broker 4
上，那么第一个跟随者副本会在
broker 2
上，
这两个
broker
在不同的机架上。如果第一个机架下线，还有其他副本仍然活跃着，所以分区
仍然可用。这对所有副本来说都是一样的，因此在机架下线时仍然能够保证可用性。
机架1 机架2
broker0
broker1 broker3
broker2
图 5-5：分配给不同机架 broker 的分区和副本
为分区和副本选好合适的
broker
之后，接下来要决定这些分区应该使用哪个目录。我们单
独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，新的分区总是被添加
到数量最小的那个目录里。也就是说，如果添加了一个新磁盘 ...
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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.