Automating AWS Infrastructure with Terraform Functions

Diagrammatic Representation

Understanding the Terraform Code

Let’s break down the provided Terraform code to understand how we automate AWS infrastructure.

1. Data Source for AWS Account ID

data "aws_caller_identity" "current" {}

This data source fetches the current AWS account ID. It’s useful for tagging and managing resources based on the account details.

2. Data Source for Latest Amazon Linux 2 AMI

data "aws_ami" "latest_amazon_linux" {
  most_recent = true
  filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
  }
  owners = ["amazon"]
}

This data source retrieves the latest Amazon Linux 2 AMI, ensuring that we use the most up-to-date image for our EC2 instances.

3. Data Source for Available AWS Availability Zones

data "aws_availability_zones" "available" {
  state = "available"
}

This data source fetches a list of available AWS availability zones, which helps in distributing resources across multiple zones for high availability.

4. Creating a VPC

resource "aws_vpc" "customvpc" {
  cidr_block       = "10.0.0.0/16"
  instance_tenancy = "default"

  tags = {
    Name = "main"
  }
}

This resource block creates a Virtual Private Cloud (VPC) with a CIDR block of 10.0.0.0/16. The VPC provides isolated networking in the AWS cloud.

5. Creating Public Subnets

resource "aws_subnet" "customsub" {
  count  = length(data.aws_availability_zones.available.names)
  vpc_id = aws_vpc.customvpc.id

  cidr_block        = "10.0.${count.index}.0/24"
  availability_zone = element(data.aws_availability_zones.available.names, count.index)

  map_public_ip_on_launch = true

  tags = {
    Name = "public-${element(data.aws_availability_zones.available.names, count.index)}"
    Type = "Public"
  }
}

This resource block creates public subnets in each availability zone. By using count and element functions, we dynamically create subnets and assign them to different availability zones, ensuring high availability and fault tolerance.

6. Creating EC2 Instances

resource "aws_instance" "custom_instances" {
  count         = length(aws_subnet.customsub)
  ami           = data.aws_ami.latest_amazon_linux.id
  instance_type = "t2.micro"
  subnet_id     = element(aws_subnet.customsub[*].id, count.index)

  tags = {
    Name = "ServerNo-${count.index}"
    Env  = "Dev"
  }
}

This resource block creates EC2 instances in the public subnets. The count and element functions ensure that instances are evenly distributed across the subnets. Each instance is tagged for easy identification and management.