Terraform Module Builder

Overview

Builds well-structured, reusable Terraform modules following best practices: main.tf, variables.tf (with validation), outputs.tf, versions.tf, remote state backend configuration, and a complete example module for a common pattern (VPC + EC2 + S3 bucket, or equivalent on other clouds).

When to Use This Skill

• Provisioning or refactoring cloud infrastructure as code.
• Creating reusable components that multiple teams or projects will use.
• The user says "Terraform", "IaC", "provision AWS", "create VPC", etc.

Prerequisites

• Terraform >= 1.5 installed.
• Cloud provider credentials configured (AWS profile, GCP application default, Azure CLI).
• Remote state backend (S3 + DynamoDB for AWS, GCS for GCP, etc.).

Steps

1. Module structure:

   modules/vpc/
     main.tf
     variables.tf
     outputs.tf
     versions.tf
   

2. variables.tf:

   • Descriptive descriptions.
   • type constraints.
   • default where safe.
   • validation blocks for important vars.

3. main.tf:

   • Resources with consistent naming (use local.name or var.name prefix).
   • Data sources.
   • Locals for computed values.

4. outputs.tf:

   • Only expose what consumers need.
   • Sensitive outputs marked.

5. State & backend:

   • Recommend remote backend from day one.
   • Provide backend.tf example (commented for module, required in root).

6. Complete example:

   • A full root module that uses the VPC module + creates an EC2 instance + S3 bucket with proper IAM.

7. Output:

   • All module files.
   • Example usage in a root main.tf.
   • terraform init/plan/apply commands.
   • State migration notes.

Examples

A complete, reusable vpc module for AWS (with public/private subnets, NAT, route tables, security groups) plus a root example that provisions a small web server behind it and an S3 bucket is included.

Edge Cases & Error Handling

• Existing resources: Use terraform import guidance.
• Multi-region / multi-account: Show workspace or provider alias patterns.
• Drift detection: Regular terraform plan in CI.

Verification

1. terraform init.
2. terraform plan — clean plan.
3. terraform apply — resources created.
4. terraform destroy — cleans up.
5. Module can be called from another repo with source = "git::..." or Terraform Registry.
6. Success: Infrastructure is reproducible, state is remote and locked, variables are validated, and the module is easy to reuse.

References

• Terraform Documentation
• Terraform Module Best Practices
• AWS Provider