Infrastructure as Code: Managing Cloud Resources with Terraform

In the age of cloud computing, managing infrastructure manually (ClickOps) is no longer scalable or reliable. Infrastructure as Code (IaC) has emerged as the standard for provisioning and managing IT infrastructure through machine-readable definition files.

What is Terraform?

Terraform, developed by HashiCorp, is an open-source tool that allows you to define both cloud and on-prem resources in human-readable configuration files that you can version, reuse, and share. It uses the HashiCorp Configuration Language (HCL).

Key Concepts

1. Declarative vs. Imperative: Terraform is declarative. You tell it what you want (e.g., "I want 3 AWS EC2 instances"), not how to do it. Terraform figures out the steps to reach that state.
2. Providers: Plugins that allow Terraform to interact with cloud providers (AWS, Azure, GCP), SaaS providers (GitHub, Datadog), and more.
3. State: Terraform stores the state of your infrastructure locally (terraform.tfstate) or remotely. This maps your real-world resources to your configuration.

The Terraform Workflow

The core workflow consists of three steps:

1. Write

You define resources in .tf files. Here is a more complex example involving variables and outputs.

main.tf

provider "aws" {
  region = var.region
}

resource "aws_s3_bucket" "example_bucket" {
  bucket = "my-unique-bucket-name-${var.environment}"
  acl    = "private"

  tags = {
    Name        = "My bucket"
    Environment = var.environment
  }
}

variables.tf

variable "region" {
  description = "AWS region"
  default     = "us-west-2"
}

variable "environment" {
  description = "Deployment environment (dev, staging, prod)"
  type        = string
}

2. Plan

Run terraform plan. Terraform creates an execution plan describing what it will do to reach the desired state. It checks the current state vs. the configuration and calculates the delta.

3. Apply

Run terraform apply. Terraform executes the plan, making the API calls to the provider to create, update, or destroy resources.

Managing State

In a team environment, you cannot store terraform.tfstate on your local laptop. You must use a remote backend like S3 with DynamoDB for state locking.

terraform {
  backend "s3" {
    bucket         = "my-terraform-state"
    key            = "global/s3/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "terraform_locks"
    encrypt        = true
  }
}

Conclusion

Terraform enables you to treat your infrastructure with the same rigor as your application code: versioned, reviewed, and automated.