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)

What Is a Custom Controller?

CRDs and CRs help you define the desired state for your CRs. There is a need for a component that makes sure that the state of the Kubernetes system matches the desired state as defined by the CR. As you have seen in earlier chapters, the Kubernetes components that do this are called controllers. Kubernetes comes up with many of these controllers whose job is to make sure that the desired state (for example, the number of replicas of Pods defined in a Deployment) is equal to the value defined in the Deployment object. In summary, a controller is a component that watches the state of resources through the Kubernetes API server and attempts to match the current state with the desired state.

The built-in controllers that are included in a standard setup of Kubernetes are meant to work with built-in objects such as Deployments. For our CRDs and their CRs, we need to write our own custom controllers.

The Relationship between a CRD, a CR, and a Controller...