Iac Terraform Orchestration Ops

Terraform Orchestration Tools

Manage Terraform/OpenTofu configurations at scale using orchestration tools. Choose the right tool for your team's workflow and scale requirements. Use TEnv to manage versions of all these tools.

Purpose

Orchestrate infrastructure deployments across multiple environments, accounts, and regions. Implement DRY principles, manage dependencies between stacks, and establish platform engineering patterns for Terraform/OpenTofu.

When to Use

• Deploy the same modules across multiple AWS accounts or environments
• Manage dependencies between Terraform configurations
• Keep Terraform configurations DRY (Don't Repeat Yourself)
• Implement GitOps workflows for infrastructure
• Detect and deploy only changed infrastructure
• Manage remote state configuration consistently
• Establish enterprise infrastructure platforms
• Migrate from monolithic Terraform to modular stacks
• Manage tool versions consistently across teams (TEnv)

Tool Comparison

Quick Start Decision Tree

Need to orchestrate Terraform?
│
├─ Simple DRY configs, few environments?
│  └─ Terragrunt
│
├─ Monorepo, change detection, CI/CD focus?
│  └─ Terramate
│
└─ Enterprise platform, many teams, component catalog?
   └─ Atmos

Terragrunt Overview

Thin wrapper that keeps Terraform code DRY with minimal overhead.

# terragrunt.hcl
include "root" {
  path = find_in_parent_folders()
}

terraform {
  source = "git::git@github.com:org/modules.git//vpc?ref=v1.0.0"
}

inputs = {
  name       = "production-vpc"
  cidr_block = "10.0.0.0/16"
}

Key Features:

• Remote state configuration inheritance
• Dependency management between modules
• Before/after hooks for custom logic
• Generate blocks for dynamic files
• Run-all for multi-module operations

See references/terragrunt.md for complete patterns.

Terramate Overview

Stack orchestration with Git-based change detection.

# terramate.tm.hcl
terramate {
  config {
    git {
      default_branch = "main"
    }
  }
}

stack {
  name        = "production-vpc"
  description = "Production VPC infrastructure"
  id          = "vpc-prod-us-west-2"
}

globals {
  environment = "production"
  region      = "us-west-2"
}

Key Features:

• Git-based change detection
• Code generation with templates
• Globals and metadata inheritance
• Parallel stack execution
• Native CI/CD integrations

See references/terramate.md for complete patterns.

Atmos Overview

Full-featured framework for enterprise infrastructure platforms.

# stacks/prod/us-west-2/vpc.yaml
import:
  - catalog/vpc/defaults

components:
  terraform:
    vpc:
      metadata:
        component: vpc
        inherits:
          - vpc/defaults
      vars:
        name: production-vpc
        cidr_block: "10.0.0.0/16"

Key Features:

• Component catalog with inheritance
• Stack configurations with imports
• Workflows for complex operations
• Vendoring for dependency management
• Deep integration with Spacelift

See references/atmos.md for complete patterns.

TEnv Overview

Unified version manager for Terraform, OpenTofu, Terragrunt, and Atmos.

# Install TEnv
brew install tenv

# Install and use specific versions
tenv tf install 1.7.0
tenv tofu install 1.8.0
tenv tg install 0.55.0
tenv atmos install 1.63.0

# Auto-detect from version files
tenv tf detect    # reads .terraform-version
tenv tofu detect  # reads .opentofu-version

Key Features:

• Single tool replaces tfenv, tofuenv, tgenv
• Automatic version detection from constraint files
• Cosign/PGP signature verification
• TENV_AUTO_INSTALL for seamless switching
• CI/CD friendly with version pinning

See references/tenv.md for complete patterns.

Common Patterns

Multi-Environment Structure

infrastructure/
├── terragrunt.hcl          # Root config (Terragrunt)
├── terramate.tm.hcl        # Root config (Terramate)
├── atmos.yaml              # Root config (Atmos)
├── modules/                # Shared modules
│   ├── vpc/
│   ├── eks/
│   └── rds/
├── environments/           # Environment configs
│   ├── dev/
│   ├── staging/
│   └── production/
└── regions/               # Regional configs
    ├── us-west-2/
    └── eu-west-1/

Multi-Account AWS Pattern

infrastructure/
├── accounts/
│   ├── management/        # AWS Organizations management
│   ├── security/          # Security tooling account
│   ├── networking/        # Transit Gateway, DNS
│   ├── development/       # Dev workloads
│   ├── staging/           # Staging workloads
│   └── production/        # Production workloads
└── modules/
    ├── account-baseline/  # Common account setup
    ├── networking/        # VPC, TGW attachments
    └── workloads/         # Application infrastructure

Dependency Management

All three tools handle dependencies differently:

Terragrunt:

dependency "vpc" {
  config_path = "../vpc"
}

inputs = {
  vpc_id     = dependency.vpc.outputs.vpc_id
  subnet_ids = dependency.vpc.outputs.private_subnet_ids
}

Terramate:

stack {
  after = ["../vpc"]
}

generate_hcl "_backend.tf" {
  content {
    data "terraform_remote_state" "vpc" {
      backend = "s3"
      config = {
        bucket = global.state_bucket
        key    = "vpc/terraform.tfstate"
      }
    }
  }
}

Atmos:

components:
  terraform:
    eks:
      vars:
        vpc_id: !terraform.output vpc vpc_id
        subnet_ids: !terraform.output vpc private_subnet_ids

CI/CD Integration

GitHub Actions Pattern

name: Infrastructure
on:
  push:
    branches: [main]
  pull_request:

jobs:
  detect-changes:
    runs-on: ubuntu-latest
    outputs:
      stacks: ${{ steps.detect.outputs.stacks }}
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      # Terramate change detection
      - uses: terramate-io/terramate-action@v1
        id: detect
        with:
          args: list --changed

  deploy:
    needs: detect-changes
    if: needs.detect-changes.outputs.stacks != '[]'
    strategy:
      matrix:
        stack: ${{ fromJson(needs.detect-changes.outputs.stacks) }}
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Deploy ${{ matrix.stack }}
        run: |
          cd ${{ matrix.stack }}
          tofu init
          tofu apply -auto-approve

Best Practices

1. Start simple - Begin with Terragrunt if new to orchestration
2. Use consistent naming - Establish naming conventions early
3. Version your modules - Pin module versions in all stacks
4. Implement change detection - Only deploy what changed
5. Separate state per stack - Avoid monolithic state files
6. Use workspaces sparingly - Prefer directory-based separation
7. Automate everything - CI/CD for all infrastructure changes
8. Document dependencies - Make cross-stack dependencies explicit
9. Test in lower environments - Promote through environments
10. Monitor drift - Regularly check for configuration drift

Reference Files

• references/terragrunt.md - Complete Terragrunt patterns and examples
• references/terramate.md - Complete Terramate patterns and examples
• references/atmos.md - Complete Atmos patterns and examples
• references/tenv.md - TEnv version management for all tools

Related Skills

• iac-terraform-modules-eng - Writing reusable Terraform modules
• cloud-aws-organizations-ops - AWS multi-account patterns