terraform-modules

Terraform Modules

Activate this skill when designing or implementing Terraform modules.

When to Use

• Creating reusable infrastructure components
• Refactoring inline resources into modules
• Designing module interfaces (variables, outputs)
• Testing infrastructure code
• Publishing modules to registries

Module Structure

modules/<module-name>/
  main.tf           Primary resource definitions
  variables.tf      Input variables with descriptions and validation
  outputs.tf        Output values for consumers
  versions.tf       Provider and Terraform version constraints
  README.md         Usage documentation with examples
  examples/         Example configurations
  tests/            Terratest or terraform test files

Design Principles

• Single responsibility: one module, one concern
• Sensible defaults: work out of the box with minimal config
• Explicit interfaces: all inputs documented with types and validation
• Composable: modules should compose with other modules cleanly
• Testable: include examples that can be used as integration tests

Rules

• Pin provider versions in versions.tf
• Add validation blocks to variables where appropriate
• Use terraform fmt before committing
• Include at least one working example
• Document all variables and outputs
• Use data sources over hardcoded values
• Never hardcode account IDs, regions, or environment names