May 2020
Beginner to intermediate
319 pages
7h 3m
Chinese
Content preview from 数据库系统内幕
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反熵和传播
｜
221
由于分布式系统的固有性质，任何节点或节点之间的链接都随时可能发生故障，从而使
这一段无法访问，并导致无法遍历树。惰性 Gossip 网络帮助节点将看到的消息通知给对
等节点，从而构造以及修复树。
图 12-5 展示了这种双重连接的示意：节点通过最优生成树（实线）和惰性 Gossip 网络
（虚线）相连。该图示不表示任何特定的网络拓扑，而仅代表节点之间的
连接
。
图
12-5
：惰性和立即推送网络。实线表示广播树，虚线表示惰性
Gossip
连接
使用惰性推送机制进行树的构建和修复的一个优点是：在负载恒定的网络中，由于最先
响应的节点会被加入广播树中，因此该算法倾向于生成一棵最小化消息延迟的树。
12.6.4
局部视图
向所有已知的对等节点广播消息、维护集群的完整视图可能会很昂贵甚至不切实际，
在
流失率
（衡量加入和离开系统的节点数量）较高时更是如此。为了避免这一代价，
Gossip 协议常常使用
对等节点采样服务
。该服务维护集群的
局部视图
，该视图定期用
Gossip 刷新。局部视图之间互相重叠，因为 Gossip 协议需要一定程度的冗余，但是过多
的冗余也意味着更多的工作负担。
例如，混合局部视图（Hybrid Partial View，HyParView）协议 [LEITAO07] 维护集群的
较小的
活跃
视图（active view）和较大的
被动
视图（passive view）。活跃视图中的节点构
成一个可用于传播消息的覆盖图。被动视图则用于维护节点列表，用于替换活跃视图中
的故障节点。
每隔一段时间，节点进行一次洗牌 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.