Infrastructure as Code: Terraform with Go

Introduction

Terraform enables defining infrastructure as code. This guide covers provisioning cloud resources, managing state, and best practices for IaC.

Core Concepts

Terraform Basics

Resources: Cloud infrastructure components
Variables: Input parameters
Outputs: Return values
State: Current infrastructure state
Modules: Reusable configurations

Good: Terraform Configuration

Basic Configuration

# ✅ GOOD: Terraform configuration
terraform {
  required_version = ">= 1.0"
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = var.aws_region
}

# ✅ GOOD: Variables
variable "aws_region" {
  description = "AWS region"
  type        = string
  default     = "us-east-1"
}

variable "app_name" {
  description = "Application name"
  type        = string
}

variable "environment" {
  description = "Environment"
  type        = string
  validation {
    condition     = contains(["dev", "staging", "prod"], var.environment)
    error_message = "Environment must be dev, staging, or prod."
  }
}

# ✅ GOOD: Resources
resource "aws_instance" "app" {
  ami           = data.aws_ami.ubuntu.id
  instance_type = "t3.micro"

  tags = {
    Name        = var.app_name
    Environment = var.environment
  }
}

# ✅ GOOD: Data sources
data "aws_ami" "ubuntu" {
  most_recent = true
  owners      = ["099720109477"]

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"]
  }
}

# ✅ GOOD: Outputs
output "instance_ip" {
  description = "Instance IP address"
  value       = aws_instance.app.public_ip
}

Modules

# ✅ GOOD: Module usage
module "vpc" {
  source = "./modules/vpc"

  cidr_block = "10.0.0.0/16"
  environment = var.environment
}

module "app" {
  source = "./modules/app"

  vpc_id = module.vpc.vpc_id
  app_name = var.app_name
}

Good: Terraform Commands

Common Commands

# ✅ GOOD: Initialize Terraform
terraform init

# ✅ GOOD: Validate configuration
terraform validate

# ✅ GOOD: Format configuration
terraform fmt -recursive

# ✅ GOOD: Plan changes
terraform plan -out=tfplan

# ✅ GOOD: Apply changes
terraform apply tfplan

# ✅ GOOD: Destroy resources
terraform destroy

# ✅ GOOD: Show state
terraform show

# ✅ GOOD: List resources
terraform state list

Advanced Patterns

Remote State

# ✅ GOOD: Remote state configuration
terraform {
  backend "s3" {
    bucket         = "terraform-state"
    key            = "prod/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-locks"
  }
}

Workspaces

# ✅ GOOD: Workspace management
terraform workspace new prod
terraform workspace select prod
terraform apply

Best Practices

1. Use Variables

# ✅ GOOD: Use variables
variable "instance_type" {
  type = string
}

resource "aws_instance" "app" {
  instance_type = var.instance_type
}

# ❌ BAD: Hardcoded values
resource "aws_instance" "app" {
  instance_type = "t3.micro"
}

2. Use Modules

# ✅ GOOD: Modular structure
module "vpc" { ... }
module "app" { ... }

# ❌ BAD: Monolithic configuration
resource "aws_vpc" { ... }
resource "aws_instance" { ... }

3. Use Remote State

# ✅ GOOD: Remote state
backend "s3" { ... }

# ❌ BAD: Local state
# State stored locally

Resources

Terraform Documentation: https://www.terraform.io/docs/
AWS Provider: https://registry.terraform.io/providers/hashicorp/aws/latest/docs
Terraform Best Practices: https://www.terraform.io/docs/cloud/guides/recommended-practices

Summary

Terraform enables managing infrastructure as code. Use modules for reusability, remote state for collaboration, and variables for flexibility. Proper IaC practices ensure reproducible, maintainable infrastructure.