Terraform Patterns

Terraform Infrastructure Patterns

When to Use This Skill

• Provisioning cloud infrastructure
• Managing infrastructure as code
• Creating reusable Terraform modules
• Multi-environment deployments
• Following Terraform best practices

Target Agents

• devops-engineer - Primary user
• cloud-architect - Infrastructure design
• infrastructure-specialist - Resource management

Core Patterns

1. Module Structure

# modules/ec2-instance/main.tf
resource "aws_instance" "this" {
  ami           = var.ami_id
  instance_type = var.instance_type

  vpc_security_group_ids = var.security_group_ids
  subnet_id              = var.subnet_id

  tags = merge(
    var.tags,
    {
      Name = var.instance_name
    }
  )
}

# modules/ec2-instance/variables.tf
variable "ami_id" {
  description = "AMI ID for EC2 instance"
  type        = string
}

variable "instance_type" {
  description = "Instance type"
  type        = string
  default     = "t3.micro"
}

variable "tags" {
  description = "Tags to apply to resources"
  type        = map(string)
  default     = {}
}

# modules/ec2-instance/outputs.tf
output "instance_id" {
  description = "ID of created instance"
  value       = aws_instance.this.id
}

output "public_ip" {
  description = "Public IP of instance"
  value       = aws_instance.this.public_ip
}

2. Remote State

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

# State locking with DynamoDB
resource "aws_dynamodb_table" "terraform_locks" {
  name         = "terraform-locks"
  billing_mode = "PAY_PER_REQUEST"
  hash_key     = "LockID"

  attribute {
    name = "LockID"
    type = "S"
  }
}

3. Multi-Environment Setup

# environments/prod/main.tf
module "vpc" {
  source = "../../modules/vpc"

  environment = "prod"
  vpc_cidr    = "10.0.0.0/16"

  tags = {
    Environment = "prod"
    Managed_by  = "terraform"
  }
}

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

  environment         = "prod"
  instance_type       = "t3.large"
  desired_capacity    = 5
  max_size            = 10
}

Best Practices

1. Use modules for reusability
2. Implement remote state
3. Use workspaces for environments
4. Version provider versions
5. Use variables and locals
6. Implement state locking
7. Use data sources for existing resources
8. Tag all resources
9. Use terraform fmt and validate
10. Store secrets in vault/ssm