terraform-stacks

# Terraform Stacks

Terraform Stacks simplify infrastructure provisioning and management at scale by providing a configuration layer above traditional Terraform modules. Stacks enable declarative orchestration of multiple components across environments, regions, and cloud accounts.

## Core Concepts

**Stack**: A complete unit of infrastructure composed of components and deployments that can be managed together.

**Component**: An abstraction around a Terraform module that defines infrastructure pieces. Each component specifies a source module, inputs, and providers.

**Deployment**: An instance of all components in a stack with specific input values. Use deployments for different environments (dev/staging/prod), regions, or cloud accounts.

**Stack Language**: A separate HCL-based language (not regular Terraform HCL) with distinct blocks and file extensions.

## File Structure

Terraform Stacks use specific file extensions:

- **Component configuration**: `.tfcomponent.hcl`
- **Deployment configuration**: `.tfdeploy.hcl`
- **Provider lock file**: `.terraform.lock.hcl` (generated by CLI)

All configuration files must be at the root level of the Stack repository. HCP Terraform processes all files in dependency order.

### Recommended File Organization

```
my-stack/
├── variables.tfcomponent.hcl        # Variable declarations
├── providers.tfcomponent.hcl        # Provider configurations
├── components.tfcomponent.hcl       # Component definitions
├── outputs.tfcomponent.hcl          # Stack outputs
├── deployments.tfdeploy.hcl         # Deployment definitions
├── .terraform.lock.hcl              # Provider lock file (generated)
└── modules/                         # Local modules (optional - only if using local modules)
    ├── vpc/
    └── compute/
```

**Note**: The `modules/` directory is only required when using local module sources. Components can reference modules from:
- Local file paths: `./modules/vpc`
- Public registry: `terraform-aws-modules/vpc/aws`
- Pr