This repository demonstrates a 3-layer Terragrunt structure with proper dependency management using local modules and null resources.

┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ Layer 2 │ │ Layer 2 │ │ Layer 2 │ │ API │ │ Frontend │ │ Analytics │ └─────────────────┘ └─────────────────┘ └─────────────────┘ │ │ │ └─────────────────────┼─────────────────────┘ │ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ Layer 1 │ │ Layer 1 │ │ Layer 1 │ │ Compute │ │ Storage │ │ Monitoring │ └─────────────────┘ └─────────────────┘ └─────────────────┘ │ │ │ └─────────────────────┼─────────────────────┘ │ ┌─────────────────────┼─────────────────────┐ │ │ │ ┌─────────────────┐ ┌─────────────────┐ │ Core │ │ Core │ │ Network │ │ Security │ └─────────────────┘ └─────────────────┘ 

. ├── terragrunt.hcl # Root configuration ├── common.tfvars # Common variables ├── core/ # Core layer (foundation) │ ├── network/ │ │ └── terragrunt.hcl │ └── security/ │ └── terragrunt.hcl ├── layer1/ # Application layer │ ├── compute/ │ │ └── terragrunt.hcl │ ├── storage/ │ │ └── terragrunt.hcl │ └── monitoring/ │ └── terragrunt.hcl ├── layer2/ # Service layer │ ├── api/ │ │ └── terragrunt.hcl │ ├── frontend/ │ │ └── terragrunt.hcl │ └── analytics/ │ └── terragrunt.hcl └── modules/ # Local Terraform modules ├── core-network/ ├── core-security/ ├── layer1-compute/ ├── layer1-storage/ ├── layer1-monitoring/ ├── layer2-api/ ├── layer2-frontend/ └── layer2-analytics/ 

• Network: Creates VPC, subnets, and basic networking infrastructure
• Security: Creates security groups and IAM roles

• Compute: Creates compute instances and load balancers (depends on network + security)
• Storage: Creates S3 buckets and RDS instances (depends on network + security)
• Monitoring: Creates CloudWatch dashboards and log groups (depends on network + security)

• API: Creates API Gateway and endpoints (depends on compute + storage)
• Frontend: Creates CloudFront distribution and web assets (depends on storage + monitoring)
• Analytics: Creates data pipelines and analytics jobs (depends on compute + storage + monitoring)

# Deploy everything in dependency order terragrunt run-all apply

# Deploy core infrastructure first terragrunt run-all apply --terragrunt-include-dir core # Deploy layer 1 terragrunt run-all apply --terragrunt-include-dir layer1 # Deploy layer 2 terragrunt run-all apply --terragrunt-include-dir layer2

# Deploy specific module cd core/network terragrunt apply # Or from root terragrunt apply --terragrunt-working-dir core/network

# Destroy in reverse dependency order terragrunt run-all destroy

1. Dependency Management: Each layer properly depends on the previous layer's outputs
2. Mock Outputs: Mock values provided for terragrunt plan without dependencies
3. Local Modules: All modules are local for easy customization and testing
4. Null Resources: Uses null resources for demonstration (replace with real resources as needed)
5. State Management: Each module has its own state file for isolation
6. Variable Inheritance: Common variables shared through root configuration

To adapt this structure for real infrastructure:

1. Replace null resources in modules with actual cloud resources
2. Update provider configurations for your cloud platform
3. Modify variables and outputs to match your requirements
4. Add environment-specific configurations
5. Configure remote state backend for production use

To verify the dependency structure:

# Generate dependency graph terragrunt graph-dependencies # Run plan to see what would be created terragrunt run-all plan