Book Image

Managing Kubernetes Resources Using Helm - Second Edition

By : Andrew Block, Austin Dewey
Book Image

Managing Kubernetes Resources Using Helm - Second Edition

By: Andrew Block, Austin Dewey

Overview of this book

Containerization is one of the best ways to implement DevOps, and learning how to execute it effectively is an essential part of a developer’s skillset. Kubernetes is the current industry standard for container orchestration. This book will help you discover the efficiency of managing applications running on Kubernetes with Helm. Starting with a brief introduction to Helm and its impact on users working with containers and Kubernetes, you’ll delve into the primitives of Helm charts and their architecture and use cases. From there, you’ll understand how to write Helm charts in order to automate application deployment on Kubernetes and work your way toward more advanced strategies. These enterprise-ready patterns are focused on concepts beyond the basics so that you can use Helm optimally, looking at topics related to automation, application development, delivery, lifecycle management, and security. By the end of this book, you’ll have learned how to leverage Helm to build, deploy, and manage applications on Kubernetes.
Table of Contents (18 chapters)
Part 1: Introduction and Setup
Part 2: Helm Chart Development
Part 3: Advanced Deployment Patterns

Helm template variables

In addition to leveraging values and other built-in objects, chart developers can create variables of their own within chart templates to provide additional processing options. A common use case for this approach is flow control, but template variables can serve other use cases as well.

A variable in a chart template is defined as follows:

{{ $myvar := "Hello World!" }}

The preceding example creates a variable called myvar and sets the value to a string equaling to Hello World!. Variables can be assigned to objects as well, such as a chart’s values, as illustrated here:

{{ $myvar := .Values.greeting }}

Once a variable is defined, it can be referenced in the following way:

  greeting.txt: |-
    {{ $myvar }}

Another example of using variables is in a range block, where variables capture the index and value of list iterations, as illustrated in the following code snippet: