Infrastructure as Code with Terraform: AWS Cloud

What is Terraform?

Terraform is an infrastructure-as-code tool that enables you to safely and predictably create, change, and improve infrastructure.

Basic Syntax

hcl

# main.tf
provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  tags = {
    Name = "WebServer"
  }
}

Variables

hcl

# variables.tf
variable "instance_type" {
  description = "EC2 instance type"
  type        = string
  default     = "t2.micro"
}

variable "environment" {
  description = "Environment name"
  type        = string
}

# terraform.tfvars
instance_type = "t2.micro"
environment   = "production"

Outputs

hcl

# outputs.tf
output "instance_public_ip" {
  description = "Public IP of the EC2 instance"
  value       = aws_instance.web.public_ip
}

output "instance_id" {
  description = "ID of the EC2 instance"
  value       = aws_instance.web.id
}

VPC Configuration

hcl

resource "aws_vpc" "main" {
  cidr_block           = "10.0.0.0/16"
  enable_dns_hostnames = true
  enable_dns_support   = true

  tags = {
    Name = "main-vpc"
  }
}

resource "aws_subnet" "public" {
  vpc_id                  = aws_vpc.main.id
  cidr_block              = "10.0.1.0/24"
  map_public_ip_on_launch = true
  availability_zone       = "us-east-1a"

  tags = {
    Name = "public-subnet"
  }
}

resource "aws_internet_gateway" "gw" {
  vpc_id = aws_vpc.main.id

  tags = {
    Name = "main-gateway"
  }
}

Security Groups

hcl

resource "aws_security_group" "web" {
  name        = "web-sg"
  description = "Allow web traffic"
  vpc_id      = aws_vpc.main.id

  ingress {
    description = "HTTP"
    from_port   = 80
    to_port     = 80
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  ingress {
    description = "HTTPS"
    from_port   = 443
    to_port     = 443
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  ingress {
    description = "SSH"
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

Load Balancer

hcl

resource "aws_lb" "web" {
  name               = "web-lb"
  internal           = false
  load_balancer_type = "application"
  security_groups    = [aws_security_group.web.id]
  subnets            = aws_subnet.public[*].id

  tags = {
    Environment = "production"
  }
}

resource "aws_lb_target_group" "web" {
  name     = "web-tg"
  port     = 80
  protocol = "HTTP"
  vpc_id   = aws_vpc.main.id

  health_check {
    path                = "/"
    interval            = 30
    timeout             = 5
    healthy_threshold   = 2
    unhealthy_threshold = 2
  }
}

RDS Database

hcl

resource "aws_db_instance" "default" {
  allocated_storage    = 20
  storage_type         = "gp2"
  engine               = "postgres"
  engine_version       = "14.7"
  instance_class       = "db.t2.micro"
  db_name              = "mydb"
  username             = "admin"
  password             = var.db_password
  parameter_group_name = "default.postgres14"
  skip_final_snapshot  = true

  vpc_security_group_ids = [aws_security_group.db.id]
  db_subnet_group_name   = aws_db_subnet_group.main.name
}

resource "aws_db_subnet_group" "main" {
  name       = "main-db-subnet-group"
  subnet_ids = aws_subnet.private[*].id

  tags = {
    Name = "My DB subnet group"
  }
}

S3 Bucket

hcl

resource "aws_s3_bucket" "assets" {
  bucket = "my-app-assets"

  tags = {
    Name = "Assets Bucket"
  }
}

resource "aws_s3_bucket_versioning" "assets" {
  bucket = aws_s3_bucket.assets.id
  versioning_configuration {
    status = "Enabled"
  }
}

resource "aws_s3_bucket_website_configuration" "assets" {
  bucket = aws_s3_bucket.assets.id

  index_document {
    suffix = "index.html"
  }

  error_document {
    key = "error.html"
  }
}

Modules

hcl

# Using modules
module "vpc" {
  source = "./modules/vpc"

  cidr_block = "10.0.0.0/16"
  environment = "production"
}

module "ec2" {
  source = "./modules/ec2"

  instance_count = 3
  instance_type  = "t2.micro"
  subnet_ids     = module.vpc.public_subnet_ids
}

State Management

hcl

# Backend configuration
terraform {
  backend "s3" {
    bucket         = "my-terraform-state"
    key            = "prod/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-state-lock"
  }
}

Commands

bash

# Initialize
terraform init

# Format code
terraform fmt

# Validate
terraform validate

# Plan changes
terraform plan

# Apply changes
terraform apply

# Destroy resources
terraform destroy

# Import existing resources
terraform import aws_instance.web i-1234567890

Best Practices

1Use version control: Track Terraform code in git
2Remote state: Store state remotely
3State locking: Prevent concurrent modifications
4Use modules: Reuse infrastructure code
5Separate environments: Dev, staging, production
6Tag resources: Organize and track costs
7Validate plans: Always review before applying
8Use variables: Make code reusable

Conclusion

Terraform enables infrastructure as code, making infrastructure management predictable and efficient.