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

Example – Python/Flask deployment with ConfigMap


This example builds on our earlier Python/Flask example. This extension will add a ConfigMap that uses both environment variables and structured files, as well as code updates to consume and use those values.

To start, add a ConfigMap with both top-level values and a deeper configuration. The top values will be exposed as environment variables, and the multiline YAML will be exposed as a file inside the container:

# CONFIGURATION FOR THE FLASK APP
kind: ConfigMap
apiVersion: v1
metadata:
  name: flask-config
data:
  CONFIG_FILE: “/etc/flask-config/feature.flags“
  feature.flags: |
    [features]
    greeting=hello
    debug=true

This ConfigMap is mapped with updates to the Pod specification of the deployment with the envFrom key and as a volume to provide the file mapping:

    spec:
      containers:
      - name: flask
        image: quay.io/kubernetes-for-developers/flask:latest
        ports:
        - containerPort: 5000
        envFrom:
...