May 2020
Beginner to intermediate
319 pages
7h 3m
Chinese
Content preview from 数据库系统内幕
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176
｜
第
9
章
时间戳列出了心跳计数器上次递增的时间。每个成员定期递增其心跳计数器，并将其列
表分发给随机相邻节点。在接收到消息时，相邻节点将列表与它自己的列表进行合并，
更新其他相邻节点的心跳计数器。
节点还定期检查状态列表和心跳计数器。如果任何节点在足够长的时间里没有更新其计
数器，就认为它发生了故障。超时时间应当谨慎选择，以将误报的概率降至最低。成员
之间通信的频率（换句话说，最坏情况下所使用的带宽）是有上限的，并且最多可以随
着系统中的进程数线性增长。
图 9-4 展示了共享心跳计数器的三个通信进程：
•
a) 这三个进程都可以进行通信并更新它们的时间戳。
•
b) P
3
不能与 P
1
通信，但它的时间戳 t
6
仍然可以通过 P
2
传播。
•
c) P
3
崩溃了。由于不再发送更新，它被其他进程检测认定为故障。
a） b） c）
图
9-4
：用于故障检测的复制心跳表
通过这样的方式，我们就可以检测出崩溃的以及任何其他集群成员都无法访问的节点。
这个决策是可靠的，因为集群的视图是来自多个节点的聚合。如果两台主机之间的链路
出现故障，心跳仍然可以通过其他进程传播。使用 Gossip 来传播系统状态增加了系统中
的消息数量，但使得信息传播更可靠。
9.4
反向故障检测
由于并不总是能传播故障的信息，并且通过通知每个成员来进行传播可能成本较高，因
此出现了一种称为
FUSE
（Failure Notification Service，故障通知服务）[DUNAGAN04]
的方法，它专注于可靠且廉价的故障传播，即使在网络分区的情况下也能工作。 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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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.