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/
├── .terraform-version               # The required Terraform version for this 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)
    ├── s3/
    └── 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
• Private registry: app.terraform.io/<org-name>/vpc/aws
• Git: git::https://github.com/org/repo.git//path?ref=v1.0.0