Preface
Kubernetes is a popular container orchestrator. It harnesses many computers together into one large computing resource and establishes a means of addressing that resource through the Kubernetes application programming interface (API). Kubernetes is open source software with origins at Google, developed over the last five years by a large group of collaborators under the auspices of the Cloud Native Computing Foundation (CNCF).
An Operator extends Kubernetes to automate the management of the entire lifecycle of a particular application. Operators serve as a packaging mechanism for distributing applications on Kubernetes, and they monitor, maintain, recover, and upgrade the software they deploy.
Who This Book Is For
If you’ve deployed applications on a Kubernetes cluster, you’ll be familiar with some of the challenges and aspirations that forged the Operator pattern. If you’ve maintained foundation services like databases and filesystems in their own ghetto outside your orchestrated clusters, and you yearn to bring them into the neighborhood, this guide to Kubernetes Operators is for you.
What You Will Learn
This book explains what an Operator is and how Operators extend the Kubernetes API. It shows how to deploy and use existing Operators, and how to create and distribute Operators for your applications using the Red Hat Operator Framework. We relate good practices for designing, building, and distributing Operators, and we explain the thinking that animates Operators with Site Reliability Engineering (SRE) principles.
After describing Operators and their concepts in the first chapter, we’ll suggest ways to get access to a Kubernetes cluster where you can do the exercises in the rest of the book. With a cluster running, you’ll deploy an Operator and observe its behavior when its application fails, scales, or gets upgraded to a new version.
Later, we will explore the Operator SDK and show you how to use it to build an Operator to naturalize an example application as a first-class Kubernetes citizen. With that practical foundation in place, we will discuss the SRE ideas from which Operators derive and the goals they share: reducing operations effort and cost, increasing service reliability, and spurring innovation by freeing teams from repetitive maintenance work.
Operator Framework and SDK
The Operator pattern emerged at CoreOS as a way to automate increasingly complex applications on Kubernetes clusters, including managing Kubernetes itself and the etcd key-value store at its heart. Work on Operators continued through an acquisition by Red Hat, leading to the 2018 release of the open source Operator Framework and SDK. The examples in this book use the Red Hat Operator SDK and the distribution mechanisms that join it in the Operator Framework.
Other Operator Tools
A community has grown up around Operators, with more than a hundred Operators for an array of applications from many vendors and projects available in Red Hat’s distribution channels alone. Several other Operator construction tools exist. We won’t discuss them in detail, but after you read this book you’ll be able to compare any of them with the Operator SDK and Framework. Other open source tools available for building Operators include Kopf for Python, Kubebuilder from the Kubernetes project, and the Java Operator SDK.
Conventions Used in This Book
The following typographical conventions are used in this book:
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Tip
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This element signifies a general note.
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Using Code Examples
Supplemental material (code examples, exercises, etc.) is available for download at https://github.com/kubernetes-operators-book/.
If you have a technical question or a problem using the code examples, please send email to [email protected].
This book is here to help you get your job done. In general, if example code is offered with this book, you may use it in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.
We appreciate, but generally do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “Kubernetes Operators by Jason Dobies and Joshua Wood (O’Reilly). Copyright 2020 Red Hat, Inc., 978-1-492-04805-3.”
If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at [email protected].
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Acknowledgments
We’d like to thank Red Hat and the OpenShift Advocacy team there for their support, in particular the steadfast and all-trades assistance of Ryan Jarvinen. We also thank the many people who reviewed, checked, suggested, and otherwise gave their time to make this work more coherent and complete, among them Anish Asthana, Evan Cordell, Michael Gasch, Michael Hausenblas, Shawn Hurley, and Jess Males.