Book Image

Kubernetes for Developers

By : Joseph Heck
Book Image

Kubernetes for Developers

By: Joseph Heck

Overview of this book

Kubernetes is documented and typically approached from the perspective of someone running software that has already been built. Kubernetes may also be used to enhance the development process, enabling more consistent testing and analysis of code to help developers verify not only its correctness, but also its efficiency. This book introduces key Kubernetes concepts, coupled with examples of how to deploy and use them with a bit of Node.js and Python example code, so that you can quickly replicate and use that knowledge. You will begin by setting up Kubernetes to help you develop and package your code. We walk you through the setup and installation process before working with Kubernetes in the development environment. We then delve into concepts such as automating your build process, autonomic computing, debugging, and integration testing. This book covers all the concepts required for a developer to work with Kubernetes. By the end of this book, you will be in a position to use Kubernetes in development ecosystems.
Table of Contents (16 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Kubernetes concepts – selectors


Selectors are used in Kubernetes to connect resources together based on the labels they have (or don’t have). A selector is meant to provide a means to retrieve a set of resources in Kubernetes.

Most of the kubectl commands support a -l option that allows you to provide a selector to filter what it finds.

A Selector can be equality-based to represent specific values, or set-based to allow filtering and selection based on multiple values. Equality selectors use = or !=. Set selectors use in, notin, and exists. You can combine these in a selector to create more complex filters and selection criteria by appending the selectors together with a , between them.

For example, you might use a label app to represent a grouping of Pods that provide service to a specific application - in this case using the value flask and tier to represent the values of front-end, cache, and back-end tiers. A selector that would return all resources related to the app might be:

app=flask...