June 2021
Intermediate to advanced
335 pages
5h 50m
Chinese
Content preview from Kubernetes编程
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概论
｜
13
1.4.1
控制循环
通常来说，控制循环是这样一段逻辑：
1.
读取资源的状态，通常采用事件驱动模式（使用
Watch
来实现，在第
3
章
中会介绍）。参考“
1.4.2
事 件 ”和“
1.4.3
边沿触发与水平触发”来了解详情。
2.
改变集群中的对象状态或集群外部系统的状态。比如：启动一个
Pod
、创
建一个网络端点或查询一个云
API
。参考“
1.4.4
改变集群对象或外部系
统状态”来了解详情。
3.
通过
API
服务器更新第
1
步中所提到的资源的状态，这个状态是存放在
etcd
中的。参考“
1.4.5
乐观并发”。
4.
循环执行这些逻辑，返回第
1
步。
不管你的控制器逻辑有多简单或多复杂，包含“读取资源状态→修改资源或
外部系统状态→更新资源状态”这三个基本步骤的逻辑结构都是一样的。下
面让我们深入看看这些步骤在
Kubernetes
控制器中是如何实现的。图
1-2
展
示了这个控制循环，它把变化的部分，也就是控制器的主循环画在图的中间。
这个主循环会在控制器进程中不断运行。控制器进程通常会在集群中的一个
Pod
里运行。
修改
包含目标状态的自
定义资源
通过Informer
得到资源
变化通知
更新资源状态
状态对账
重新同步
定时器
发生错误（冲突）后重新加入队列
（不同的工作队列会可能使用不
同的延迟和退避策略）
把资源或外部系
统的状态变成期
望的样子
资源或外部
系统的状态
图
1
-
2
：Kubernetes 的控制循环
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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.