Terragrunt - Simplifying Terraform Management

What is Terragrunt?

Terragrunt is a thin wrapper for Terraform that helps manage and reduce complexity in infrastructure-as-code (IaC) workflows. It streamlines Terraform configurations by promoting DRY (Don't Repeat Yourself) principles, enforcing best practices, and handling remote state management more efficiently.

Why Use Terragrunt?

Terraform is a powerful tool for managing cloud infrastructure, but as projects scale, managing multiple configurations, environments, and modules becomes cumbersome. This is where Terragrunt shines, offering:

• Code Reusability: Avoid duplicating configurations across environments.
• Remote State Management: Enforce consistent backend configurations.
• Dependency Management: Ensure proper sequencing of module execution.
• Workflow Simplification: Reduce boilerplate and enforce standards across teams.

Key Features of Terragrunt

1. DRY Terraform Configurations

Terragrunt enables hierarchical configuration using terragrunt.hcl files, allowing teams to store common configurations in a single place.

Example:

remote_state {
  backend = "s3"
  config = {
    bucket         = "my-terraform-state"
    key            = "state/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-lock"
  }
}

This ensures every environment uses the same remote state configuration without copy-pasting it into every Terraform module.

2. Managing Multiple Environments

With Terragrunt, teams can manage multiple environments (e.g., dev, staging, prod) using a single configuration structure.

Directory Structure:

infra/
├── terragrunt.hcl  # Common configurations
├── dev/
│   ├── terragrunt.hcl  # Dev-specific configurations
│   ├── app/
│   ├── database/
├── prod/
    ├── terragrunt.hcl  # Prod-specific configurations
    ├── app/
    ├── database/

Each environment inherits from the root configuration but allows customization.

3. Handling Dependencies

Terragrunt helps orchestrate dependencies between modules. For example, an application module may depend on a database module.

Example:

dependency "database" {
  config_path = "../database"
}
inputs = {
  db_endpoint = dependency.database.outputs.db_endpoint
}

This ensures Terraform applies the database first before deploying the application.

4. Automatic Remote State Configuration

Instead of defining backend configurations manually in each Terraform module, Terragrunt centralizes them in terragrunt.hcl and applies them automatically.

How to Get Started with Terragrunt

1. Install Terragrunt

You can install Terragrunt using Homebrew (for macOS) or download it from the official releases:

brew install terragrunt

Or manually:

wget https://github.com/gruntwork-io/terragrunt/releases/latest/download/terragrunt_linux_amd64
chmod +x terragrunt
mv terragrunt /usr/local/bin/

2. Set Up Your Project

• Define your Terraform modules.
• Create terragrunt.hcl in each environment.
• Configure remote state and dependencies.

3. Run Terragrunt Commands

Instead of running Terraform directly, use Terragrunt:

terragrunt run-all plan
terragrunt run-all apply

This executes Terraform across multiple modules while respecting dependencies.

Best Practices

• Use a Consistent Folder Structure: Follow a predictable directory structure for environments and modules.
• Leverage Inputs and Outputs: Pass variables between modules using Terragrunt dependencies.
• Enforce Remote State: Prevent state drift by using a central backend.
• Automate with CI/CD: Integrate Terragrunt with GitHub Actions, GitLab CI, or Jenkins.

Conclusion

Terragrunt enhances Terraform by simplifying configuration management, enforcing best practices, and streamlining workflows. It’s a must-have tool for DevOps teams managing large-scale infrastructure.

If you’re using Terraform extensively, consider adopting Terragrunt to improve efficiency and maintainability.