Building a Kubernetes operator usually means writing a Go controller; KUDO lets you build one declaratively, describing the whole application lifecycle in YAML instead of code.

Welcome to KUDO: Building Kubernetes Operators Declaratively.

KUDO — the Kubernetes Universal Declarative Operator — is a toolkit and runtime for writing operators without writing controller code. An operator is the standard Kubernetes pattern for running a complex stateful application, encoding the operational knowledge a human expert would use to deploy, upgrade, back up, and repair it; the usual way to build one is to write a Go controller, which is a substantial software project in its own right. KUDO replaces that with declarative packages: you describe an Operator, an OperatorVersion holding templates and parameters, and Instances that bring the application to life, and you orchestrate every lifecycle action as a Plan made of phases, steps, and tasks. The KUDO manager — a controller already running in your cluster — reads those packages and executes the plans for you. This book begins with the problem operators solve and what KUDO is, then works through its object model, the templating and parameter system, the plan execution engine, the command-line workflow, and how to package and share operators, before closing with a practical look at where KUDO fits and how to use it well.

This title is part of the ShriIra library and is free to read in full, right here — our small contribution to making world-class knowledge easy to reach.

A note on reading it: open the Contents menu at the top of the reader to jump between chapters, use the Aa menu to set a comfortable text size, theme (light, sepia, or night), and single- or two-page layout. Your place is saved automatically, so you can always pick up where you left off.

We hope it serves you well.

— Shriira Press

Contents

1. Chapter 1 — What KUDO Is
2. Chapter 2 — The Operator Problem
3. Chapter 3 — The KUDO Object Model
4. Chapter 4 — Templates and Parameters
5. Chapter 5 — Plans, Phases, Steps, and Tasks
6. Chapter 6 — The KUDO Manager and Plan Execution
7. Chapter 7 — The Command Line and Packaging
8. Chapter 8 — KUDO in Practice