Tf Module

Duplocloud Terraform Module Expert

Create and manage Terraform modules following Duplocloud patterns using terraform-duplocloud-components.

Topological Hierarchy

Portal (Duplocloud instance)
  └── Infrastructure (VPC/GKE cluster)
      ├── Shared Tenant (databases, caches)
      ├── Operators Tenant (Kubernetes operators)
      └── Application Tenants (dev01, stg01, prod01)

Each layer maps to a Terraform module with workspace instances.

Repository Patterns

Pattern 1: Infra Repo (infra-starter)

Centralized infrastructure repo (e.g., duplocloud-infra, <company>-infra):

<project>-infra/
├── modules/
│   ├── portal/           # Required: Once per Duplocloud
│   ├── infrastructure/   # Required: VPC/cluster
│   ├── shared/           # Required: Databases, caches
│   ├── tenant/           # Required: App environments
│   ├── operators/        # Required: K8s operators
│   ├── devops/           # Optional: CI/CD secrets
│   └── <app>/            # Optional: Centralized apps
├── config/<module>/<workspace>/<module>.tfvars
└── .github/workflows/

Pattern 2: Embedded App Module (Recommended for apps)

App module lives in the application's own repo:

<app-repo>/
├── src/                  # Application code
├── terraform/            # Embedded app module
│   ├── main.tf
│   ├── providers.tf
│   ├── variables.tf
│   └── outputs.tf
├── config/<workspace>/<module>.tfvars
└── .github/workflows/

Identifying Context

The tf CLI

Use the tf wrapper command instead of raw terraform. It auto-configures backends and discovers tfvars.

tf init -chdir=modules/tenant     # Auto-configures backend
tf ctx dev01                      # Select/create workspace
tf plan -chdir=modules/tenant     # Auto-loads tfvars
tf apply -chdir=modules/tenant

See: references/tf-cli.md for full documentation and equivalent terraform commands.

Core Pattern: module.ctx

Every module uses the context module for data lookups, JIT credentials, and workspace references:

module "ctx" {
  source  = "duplocloud/components/duplocloud//modules/context"
  version = "0.0.41"
  admin   = true
  workspaces = {
    tenant = {}  # Empty = terraform.workspace is tenant name
  }
}

locals {
  tenant = module.ctx.workspaces.tenant
}

See: references/context-module.md for JIT credentials, workspace references, and advanced patterns.

Module Type Quick Reference

Detailed patterns: See references/<module-type>.md files.

Common Patterns

• Database setup: references/database.md - Parent-child tenants, credential flow
• Helm deployments: references/helm.md - Values templating, chart categories
• Ephemeral envs: references/ephemeral.md - PR previews (tenant + app only)
• Naming conventions: references/naming.md - Workspace/tenant naming rules
• AWS patterns: references/aws.md - S3 backend, JIT credentials
• GCP patterns: references/gcp.md - GCS backend, Cloud SQL

Creating a New Module

Option 1: Use the init script

python scripts/init_module.py myapp --type app --cloud aws
python scripts/init_module.py myapp --type app --cloud gcp --path ./

Option 2: Copy from templates

Templates in assets/ directory:

• assets/app/ - App module files
• assets/tenant/ - Tenant module files
• assets/shared/ - Shared module files
• assets/workflow/ - GitHub Actions templates
• assets/config/ - Tfvars templates

Option 3: Manual creation

1. Create modules/<name>/ with: main.tf, providers.tf, variables.tf, outputs.tf
2. Add module.ctx with appropriate workspaces
3. Create config/<name>/<workspace>/<name>.tfvars
4. Create .github/workflows/<name>.yml

Validating Modules

python scripts/validate_module.py modules/myapp
python scripts/validate_module.py . --all  # Validate all modules

GitHub Actions

See: references/workflows.md for CI/CD patterns.

Base workflow in assets/workflow/tf-module.yml handles:

• Terraform init with auto-backend config
• Workspace selection
• Plan/apply/destroy commands
• PR comments with plan output

Decision Protocol

New Module vs New Instance?

• New Instance: Same resources, different config → add config/<module>/<name>/<module>.tfvars
• New Module: Different resources → create modules/<name>/

Which Module Type?

1. Shared across tenants? → shared
2. Kubernetes operators/CRDs? → operators
3. Environment (dev/stg/prod)? → tenant
4. App deployment? → app (with tenant = {})

Getting More Information

For authoritative documentation:

• Search Duplocloud docs using available documentation tools
• Web search for latest terraform-duplocloud-components version
• Check Terraform Registry

Secrets Pattern

Never pass secrets through variables. Only DUPLO_TOKEN should be needed.

Pattern:

1. Module A creates empty secret placeholder (value ignored)
2. User manually populates secret value
3. Module B reads secret via data block, injects into provider

See: references/secrets.md

Skill Resources