June 2021
Intermediate to advanced
335 pages
5h 50m
Chinese
Content preview from Kubernetes编程
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38
｜
第
2
章
下面我们将在
API
服务器的上下文中进一步讨论有关规格（期望状态）和当
前状态（观测状态）的细节。
“规格”用于描述对某种资源所期望的状态，可以通过
kubectl
命令行工具
或者通过
Go
代码编程来提供给
Kubernetes
集群。“当前状态”用于描述对
象的观测状态或实际状态，它由控制平面管理，可能是通过其中的核心组件
（比如控制器管理器），也可能是通过自定义控制器（参考“
1.4
控制器和
Operator
”）。比如在一个
Deployment
中，你指定了应用在运行过程中需要
始终保持
20
个副本。控制平面的控制器管理器中的
Deployment
控制器会读
取你提供的规格并创建一个
ReplicaSet
，这 个
ReplicaSet
会负责管理各个副本：
它会创建指定数量的
Pod
，最终由
kubelet
在工作节点上拉起相应的容器。
如果任何一个副本发生了问题，
Deployment
控制器会把这个状态反映到当前
状态中。这就是我们所谓的声明式状态管理，也就是说只需要声明期望的状态，
剩下事情由
Kubernetes
系统来负责解决。
下一节通过命令行来探索
API
时，我们就将看到声明式状态管理的实际例子。
2.2
通过命令行使用
API
在这一节中，我们会使用
kubectl
和
curl
来演示如何使用
Kubernetes API
。
如果你还不熟悉这些命令行工具，建议你先把它们安装好，并自己尝试一下。
作为初学者，我们先来看看如何获取资源的期望状态和观测状态。我们会使
用几乎所有集群中都会存在的控制平面组件进行演示：
kube-system ...
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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.
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.