How Terraform works

▪ An important part of Terraform (TF) is that TF knows:

● our desired state (config file)

● keeps track of our existing real infrastructure (in a state file)

▪ TF compares our desired with actual state to know which changes it needs to make to our infrastructure

▪ Without state, we would always have to check the current state ourselves and see how to update our desired state!

Core workflow

Terraform Core

Terraform core uses two input sources to do its job.

▪ The first input source is a Terraform configuration that you, as a user, configure. Here, you define what needs to be created or provisioned.

▪ And the second input source is a state where terraform keeps the up-to-date state of how the current set up of the infrastructure looks like.

So, what terraform core does is it takes the input, and it figures out the plan of what needs to be done. It compares the state, what is the current state, and what is the configuration that you desire in the end result. It figures out what needs to be done to get to that desired state in the configuration file. It figures what needs to be created, what needs to be updated, what needs to be deleted to create and provision the infrastructure.

Providers

The second component of the architecture are providers for specific technologies. This could be cloud providers like AWS, Azure, GCP, or other infrastructure as a service platform. It is also a provider for more high-level components like Kubernetes or other platform-as-a-service tools, even some software as a self-service tool.

It gives you the possibility to create infrastructure on different levels.

For example – create an AWS infrastructure, then deploy Kubernetes on top of it and then create services/components inside that Kubernetes cluster.

Terraform has over a hundred providers for different technologies, and each provider then gives terraform user access to its resources. So through AWS provider, for example, you have access to hundreds of AWS resources like EC2 instances, the AWS users, etc. With Kubernetes provider, you access to commodities, resources like services and deployments and namespaces, etc.

So, this is how Terraform works, and this way, it tries to help you provision and cover the complete application setup from infrastructure all the way to the application.