terraform

Terraform Infrastructure as Code

Instructions

1. Assess the infrastructure need: Single resource, module, or complete environment.
2. Follow Terraform best practices:
   • Use modules for reusability
   • Remote state with locking
   • Use workspaces or directories for environments
   • Version pin providers
3. Provide complete configurations: Include variables, outputs, and provider setup.
4. Guide on state management: Remote backends, state locking, import/migration.

Basic Structure

# main.tf
terraform {
  required_version = ">= 1.5.0"

  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }

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

provider "aws" {
  region = var.aws_region

  default_tags {
    tags = {
      Environment = var.environment
      ManagedBy   = "Terraform"
      Project     = var.project_name
    }
  }
}

# variables.tf
variable "aws_region" {
  description = "AWS region"
  type        = string
  default     = "us-east-1"
}

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

variable "project_name" {
  description = "Project name for tagging"
  type        = string
}

# outputs.tf
output "vpc_id" {
  description = "VPC ID"
  value       = aws_vpc.main.id
}

output "public_subnets" {
  description = "Public subnet IDs"
  value       = aws_subnet.public[*].id
}

Common Resources

VPC and Networking

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

  tags = {
    Name = "${var.project_name}-vpc"
  }
}

resource "aws_subnet" "public" {
  count                   = length(var.availability_zones)
  vpc_id                  = aws_vpc.main.id
  cidr_block              = cidrsubnet(aws_vpc.main.cidr_block, 8, count.index)
  availability_zone       = var.availability_zones[count.index]
  map_public_ip_on_launch = true

  tags = {
    Name = "${var.project_name}-public-${count.index + 1}"
  }
}

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

resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.main.id
  }
}