Book Image

Getting Started with Terraform - Second Edition

By : Kirill Shirinkin
1 (1)
Book Image

Getting Started with Terraform - Second Edition

1 (1)
By: Kirill Shirinkin

Overview of this book

Terraform is a tool used to efficiently build, configure, and improve the production infrastructure. It can manage the 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 the complete management of infrastructure with Terraform, starting with the basics of using providers and resources. It 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. The book ends with the complete workflow of managing a production infrastructure as code—this is achieved with the help of version control and continuous integration. The readers will also learn how to combine multiple providers in a single template and manage different code bases with many complex modules. It focuses on how to set up continuous integration for the infrastructure code. The readers will be able to use Terraform to build, change, and combine infrastructure safely and efficiently.
Table of Contents (15 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Understanding dependency graph

Terraform doesn't simply build your resources and write their configuration into a state file. Internally, it also manages a dependency graph of all the resources you have. It's hard to see with a single resource, but now we have two interconnected resources: VPC and a subnet. The latter one depends on the existence of the first one. But wait, what is a dependency graph anyway?

First of all, let's recall what a graph is. We won't go deep into mathematical formulas and advanced graph theories and examples here. Graph theory is big, and there are so many applications of it.

Though there are many definitions of a graph, which differ depending on the knowledge area and industry, the simplest description is a set of nodes and edges, where edges represent a connection between two nodes. It's easier to look at a graph than to read about one:

Here, we have two nodes connected to each other. Nothing really complicated. What is a dependency graph then? Let's steal a definition...