Auto Scaling and Load Balancing Using Terraform

Objective

The goal of this task is to implement a highly available and scalable architecture in AWS using Auto Scaling Group (ASG) and an Elastic Load Balancer (ELB). Terraform will be used to provision the infrastructure.

Task Architecture

1. AWS VPC
   • A dedicated VPC for networking.
   • Subnets in different availability zones for high availability.
   • Internet Gateway for outbound traffic.
2. Security Groups
   • Allow HTTP/HTTPS traffic to the Load Balancer.
   • Restrict SSH access to a specific IP range.
   • Secure EC2 instances behind the Load Balancer.
3. Application Load Balancer (ALB)
   • Distributes incoming traffic across multiple EC2 instances.
   • Health checks to ensure only healthy instances receive traffic.
4. Auto Scaling Group (ASG)
   • Ensures scalability and fault tolerance.
   • Uses Launch Template to define instance configurations.
   • Automatically adjusts instance count based on demand.
5. Terraform Modules
   • VPC Module: Manages VPC, subnets, and networking components.
   • Security Group Module: Defines security groups.
   • ALB Module: Creates the Load Balancer and Target Groups.
   • ASG Module: Provisions the Auto Scaling Group with policies.

Implementation Steps

1. Set Up Terraform Directory Structure

terraform-project/
│── modules/
│   ├── vpc/
│   ├── security-groups/
│   ├── alb/
│   ├── asg/
│── main.tf
│── variables.tf
│── outputs.tf
│── terraform.tfvars
│── providers.tf
    

2. Define VPC Module (modules/vpc/main.tf)

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "3.11.0"
  
  name = "auto-scaling-vpc"
  cidr = "10.0.0.0/16"
  
  azs             = ["us-east-1a", "us-east-1b"]
  public_subnets  = ["10.0.1.0/24", "10.0.2.0/24"]
  
  enable_dns_hostnames = true
  enable_dns_support   = true
}
    

3. Define Security Groups (modules/security-groups/main.tf)

resource "aws_security_group" "elb_sg" {
  name        = "elb-security-group"
  description = "Allow HTTP and HTTPS traffic"
  vpc_id      = module.vpc.vpc_id
  
  ingress {
    from_port   = 80
    to_port     = 80
    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"]
  }
}
    

4. Define Application Load Balancer (ALB) (modules/alb/main.tf)

module "alb" {
  source  = "terraform-aws-modules/alb/aws"
  version = "7.1.0"

  name               = "autoscaling-alb"
  load_balancer_type = "application"
  vpc_id             = module.vpc.vpc_id
  subnets            = module.vpc.public_subnets
  security_groups    = [aws_security_group.elb_sg.id]

  target_groups = [
    {
      name     = "asg-target-group"
      port     = 80
      protocol = "HTTP"
      vpc_id   = module.vpc.vpc_id
    }
  ]
}
  

5. Define Auto Scaling Group (ASG) (modules/asg/main.tf)

module "asg" {
  source = "terraform-aws-modules/autoscaling/aws"

  name                = "web-asg"
  min_size           = 2
  max_size           = 5
  desired_capacity   = 2
  vpc_zone_identifier = module.vpc.public_subnets

  launch_template = {
    id      = aws_launch_template.web.id
    version = "$Latest"
  }

  target_group_arns = module.alb.target_group_arns
}

    

6. Define Launch Template (modules/asg/launch-template.tf)

resource "aws_launch_template" "web" {
  name          = "web-launch-template"
  image_id      = "ami-0c55b159cbfafe1f0"  # Replace with your region-specific AMI ID
  instance_type = "t2.micro"

  network_interfaces {
    associate_public_ip_address = true
    security_groups             = [aws_security_group.elb_sg.id]
  }

  user_data = base64encode(<<-EOF
              #!/bin/bash
              sudo apt update -y
              sudo apt install -y apache2
              echo "Hello, Terraform!" > /var/www/html/index.html
              sudo systemctl start apache2
              sudo systemctl enable apache2
              EOF
  )
  }  

7. Define Outputs (outputs.tf)

output "alb_dns_name" {
  description = "Load Balancer DNS Name"
  value       = module.alb.lb_dns_name
}

8. Deploy Infrastructure

1. Initialize Terraform

terraform init

2. Plan the Deployment

terraform plan

3. Apply the Configuration

terraform apply -auto-approve

Validation

1. Verify Load Balancer.
   • Go to AWS Console → EC2 → Load Balancers.
   • Copy the DNS Name and open it in a browser.
   • You should see the "Hello, Terraform!" message.
2. Check Auto Scaling by terminating an instance manually.
   • Terminate an instance manually and observe if it is replaced automatically.
   • Simulate a load test to trigger scaling policies.

Cleanup

If you want to destroy the infrastructure:

terraform destroy -auto-approve
    

Conclusion

This project successfully provisions a highly available and scalable infrastructure using Terraform modules. The Auto Scaling Group (ASG) ensures resilience, while the Elastic Load Balancer (ELB) distributes traffic efficiently.