Module 3: Building Custom Controllers

Overview

Now that you’ve built your first operator in Module 2, it’s time to dive deeper into building sophisticated controllers. This module teaches you the advanced patterns and techniques needed to build production-ready operators that manage complex applications.

Duration: 6-7 hours
Prerequisites:

Completion of Module 1: Kubernetes Architecture Deep Dive
Completion of Module 2: Introduction to Operators
Understanding of the basic operator pattern

Learning Objectives

By the end of this module, you will:

Understand controller-runtime architecture in depth
Design well-structured APIs for your operators
Implement robust reconciliation logic
Work effectively with the Kubernetes client
Build a database operator that manages PostgreSQL

Module Structure

Prerequisites Check

Before starting, ensure you’ve completed:

✅ Module 1: Understand CRDs, controllers, and reconciliation
✅ Module 2: Built your first “Hello World” operator
✅ Can scaffold kubebuilder projects
✅ Understand the Reconcile function basics

If you haven’t completed Module 2, start with Module 2: Introduction to Operators.

What You’ll Build

Throughout this module, you’ll build a PostgreSQL operator that:

Manages PostgreSQL database instances
Handles database creation and configuration
Manages StatefulSets and Services
Implements proper reconciliation logic
Uses owner references for resource management

This builds on your “Hello World” operator from Module 2, adding complexity and real-world patterns.

Setup

Before starting this module:

Verify Module 2 completion:
- You should have built a “Hello World” operator
- You understand kubebuilder project structure
- You can run operators locally
Ensure development environment is ready:
```
./scripts/setup-dev-environment.sh
```
Have a kind cluster running:
```
./scripts/setup-kind-cluster.sh
```

Hands-on Labs

Each lesson includes hands-on exercises building toward a complete PostgreSQL operator.

Solutions

Complete working solutions for all labs are available in the solutions directory:

Lab 3.3 Solutions - Complete Database operator (types, controller with StatefulSet/Service)