Book Image

The Kubernetes Operator Framework Book

By : Michael Dame
1 (1)
Book Image

The Kubernetes Operator Framework Book

1 (1)
By: Michael Dame

Overview of this book

From incomplete collections of knowledge and varying design approaches to technical knowledge barriers, Kubernetes users face various challenges when developing their own operators. Knowing how to write, deploy, and pack operators makes cluster management automation much easier – and that's what this book is here to teach you. Beginning with operators and Operator Framework fundamentals, the book delves into how the different components of Operator Framework (such as the Operator SDK, Operator Lifecycle Manager, and OperatorHub.io) are used to build operators. You’ll learn how to write a basic operator, interact with a Kubernetes cluster in code, and distribute that operator to users. As you advance, you’ll be able to develop a sample operator in the Go programming language using Operator SDK tools before running it locally with Operator Lifecycle Manager, and also learn how to package an operator bundle for distribution. The book covers best practices as well as sample applications and case studies based on real-world operators to help you implement the concepts you’ve learned. By the end of this Kubernetes book, you’ll be able to build and add application-specific operational logic to a Kubernetes cluster, making it easier to automate complex applications and augment the platform.
Table of Contents (16 chapters)
1
Part 1: Essentials of Operators and the Operator Framework
4
Part 2: Designing and Developing an Operator
9
Part 3: Deploying and Distributing Operators for Public Use

Adding health checks

Health checks (also known as liveness and readiness probes) are a way for any Pod to make its current functional state discoverable by other components in the cluster. This is usually done by way of exposing an endpoint in the container (traditionally /healthz for liveness checks and /readyz for readiness). That endpoint can be reached by other components (such as the kubelet) to determine whether the Pod is healthy and ready to serve requests. The topic is covered in detail in the Kubernetes documentation at https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/.

The code initialized by the Operator SDK in main.go contains the healthz and readyz check setup by default:

main.go

import (
  ...
  "sigs.k8s.io/controller-runtime/pkg/healthz"
)
func main() {
...
   mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(),   ctrl.Options{
...