Book Image

Getting Started with Terraform

By : Kirill Shirinkin
Book Image

Getting Started with Terraform

By: Kirill Shirinkin

Overview of this book

Terraform is a tool used to efficiently build, configure, and improve production infrastructure. It can manage existing infrastructure as well as create custom in-house solutions. This book shows you when and how to implement infrastructure as a code practices with Terraform. It covers everything necessary to set up complete management of infrastructure with Terraform, starting with the basics of using providers and resources. This book is a comprehensive guide that begins with very small infrastructure templates and takes you all the way to managing complex systems, all using concrete examples that evolve over the course of the book. It finishes with the complete workflow of managing a production infrastructure as code – this is achieved with the help of version control and continuous integration. At the end of this book, you will be familiar with advanced techniques such as multi-provider support and multiple remote modules.
Table of Contents (15 chapters)
Getting Started with Terraform
About the Author
About the Reviewer
Customer Feedback

Controlling dependencies with depends_on and ignore_changes

In 99% of cases, Terraform will resolve dependencies automatically. There are two problems you can encounter when you rely solely on automatic resolution:

  • Dependency is not automatically handled by Terraform

  • Dependency leads to unwanted behavior and should be omitted

For both problems, there is a solution in Terraform. Let's first look at how you can force dependencies with depends_on. For each resource, you can specify the depends_on parameter, which accepts a list of resources that this resource depends on. As a result, this resource won't be created until the ones listed inside this parameter are created.

There might be different use cases for this. For example, your private OpenStack installation could be implemented in a way that it is impossible to create virtual routers in parallel, so you have to force dependency for each router to force Terraform to create them one after another. Or your instances could depend on the existence...