Book Image

The Kubernetes Workshop

By : Zachary Arnold, Sahil Dua, Wei Huang, Faisal Masood, Mélony Qin, Mohammed Abu Taleb
Book Image

The Kubernetes Workshop

By: Zachary Arnold, Sahil Dua, Wei Huang, Faisal Masood, Mélony Qin, Mohammed Abu Taleb

Overview of this book

Thanks to its extensive support for managing hundreds of containers that run cloud-native applications, Kubernetes is the most popular open source container orchestration platform that makes cluster management easy. This workshop adopts a practical approach to get you acquainted with the Kubernetes environment and its applications. Starting with an introduction to the fundamentals of Kubernetes, you’ll install and set up your Kubernetes environment. You’ll understand how to write YAML files and deploy your first simple web application container using Pod. You’ll then assign human-friendly names to Pods, explore various Kubernetes entities and functions, and discover when to use them. As you work through the chapters, this Kubernetes book will show you how you can make full-scale use of Kubernetes by applying a variety of techniques for designing components and deploying clusters. You’ll also get to grips with security policies for limiting access to certain functions inside the cluster. Toward the end of the book, you’ll get a rundown of Kubernetes advanced features for building your own controller and upgrading to a Kubernetes cluster without downtime. By the end of this workshop, you’ll be able to manage containers and run cloud-based applications efficiently using Kubernetes.
Table of Contents (20 chapters)
Preface

How Admission Controllers Work

Kubernetes provides a set of more than 25 admission controllers. A set of admission controllers is enabled by default and the cluster administrator can pass flags to the API server to control enabling/disabling the additional controllers (configuring the API server in a production-grade cluster is outside the scope of this book). These can be broadly divided into two types:

  • Mutating admission controllers allow you to modify the request before it gets applied to the Kubernetes platform. LimitRanger is one such example, which applies the defaultRequests to the Pod if it is undefined by the Pod itself.
  • Validating admission controllers validate the request and cannot change the request object. If this controller rejects the request, it will not be actioned by the Kubernetes platform. An example of this would be the NamespaceExists controller, which rejects the request if the namespace referenced in the request is not available.

Essentially...