Kubernetes Operators Advanced

This course covers Golang operator reconciliation, use of OLM, and use of Scorecard.

Reconciliation
Operators mimic the behavior of core Kubernetes components in many ways, chief among them the process of reconciliation. When a user creates an instance of your operator’s type, one or more controllers is responsible for creating that desired state. This course covers the creation of a basic reconcile loop in Golang to create a simple Memcached operator, similar to the Golang operator from the Intermediate course.

Operator Lifecycle Manager (OLM)
OLM is a tool for installing and upgrading operators on a Kubernetes cluster. Operator authors create a Bundle for each version of their operator, which is then published and consumed by OLM. This course covers the creation of a bundle for the simple Memcached operator from above, and then covers the upgrade case by adding a new field, implements migration via conversion webhook, creates a new bundle, and upgrades the deployed operator in-place.

Scorecard
Scorecard is an Operator-sdk command for scaffolding and running test frameworks on a deployed operator. This course first covers using Scorecard to automatically generate and run a basic verification test suite. Then, it shows how to create your own custom test suite with a non-trivial unit test for the above simple Memcached operator.

Learning Objectives
In this course, you will learn about:
– How reconciliation logic works in Kubernetes controllers
– Constructing your own reconcile loop in a Golang operator
– Getting an introduction to the Operator Lifecycle Manager (OLM)
– Deploying and managing an operator using OLM
– Using Scorecard to create a test suite for your operator

Course Syllabus
Module 1 – Golang Operator Reconciliation
Overview of Kubernetes controller reconciliation
Kubernetes’ declarative API
Explanation of Memcached operator reconciliation via finite state diagram
Hands-on Lab
Build a simple Golang operator with Operator SDK
Write reconciliation loop using controller-runtime library
Module 2 – Operator Lifecycle Manager
Overview of Operator Lifecycle Manager (OLM)
What is OLM?
What is an operator bundle
Hands-on Lab 1
Install OLM on your cluster
Package a Golang operator with OLM
Deploy it to the cluster using OLM
Hands-on Lab 2
Update operator with a breaking change
Create a conversion webhook to manage the upgrade
Use OLM to upgrade operator in-place
Module 3 – Testing your operator with Scorecard
Overview of Scorecard, an Operator SDK tool for building test images for a deployed operator
Hands-on Lab
Build a Scorecard test suite for Memcached operator
Write an integration test for Memcached operator

Course Prerequisites
Basic familiarity with Kubernetes, including using kubectl to create resources on a Kubernetes cluster. You should know how to create, update, and delete Kubernetes resources such as Pods and Services.
Understanding of the basic construction, deployment, and use of operators
Completion of the Intermediate course on Kubernetes operators

The requirements of the hands-on labs are as follows:
Requirements for all hands-on labs
Operator SDK v1.5.0+ installed
Kubectl v1.17.0+ installed
Admin access to a Kubernetes cluster. Note that the version of Operator Lifecycle Manger currently(8/23/21) on IMB Cloud’s Kubernetes Service is incompatible with this tutorial. For running a cluster locally, see the Minikube docs.
Docker v3.2.2+ installed
Access to a Docker image repository such as Docker Hub or quay.io
Golang v1.16.0+ installed
Module 1 Lab requirements
No additional requirements
Module 2 Lab requirements
Operator Lifecycle Manager installed on your Kubernetes cluster. The Operator-sdk command operator-sdk olm install will install a compatible version of OLM on your cluster. Note that currently(8/23/21) the version of OLM installed on IBM Cloud IKS clusters is incompatible with this tutorial.
Module 3 Lab requirements
No additional requirements