Sourcing a Module From the Terraform Registry

Leverage the Terraform Registry to discover, share, and reuse community-maintained modules. When you integrate Terragrunt, you can reference these modules directly using the tfr:// protocol.

1. Referencing a Module in Terragrunt

In your terragrunt.hcl file, set the source attribute to point at a Registry module:

# terragrunt.hcl
terraform {
  source = "tfr://<namespace>/<module_name>/<provider>"
}

Example:

terraform {
  source = "tfr://terraform-aws-modules/vpc/aws"
}

2. Initializing the Configuration

Run the following command to download and prepare the module in your working directory:

terragrunt init

This initializes your Terragrunt configuration and fetches the specified module from the Terraform Registry.

3. Pinning a Module Version

To guarantee reproducible builds and avoid unintended upgrades, specify a version constraint:

terraform {
  source  = "tfr://terraform-aws-modules/vpc/aws"
  version = "~> 3.0"
}

Modules in the Registry follow semantic versioning. Locking to ~> 3.0 ensures you get all non-breaking updates in the 3.x series.

4. Updating to the Latest Matching Version

When you’re ready to pull in the newest matching release (within your version constraint), use:

terragrunt get --update

This command refreshes your local copy of the module, incorporating any fixes or enhancements.

5. Security and Best Practices

• Review module inputs, outputs, and provisioners for security compliance.
• Check the Terraform Registry page for the module’s documentation and changelog.
• Use version pinning to control when features and fixes are introduced.

Links and References

• Terraform Registry
• Terragrunt Documentation
• Terraform Modules Best Practices