Innovative Software Technology

Revolutionizing Terraform Module Management with Nx

Managing Infrastructure as Code (IaC) with Terraform presents unique challenges as organizations grow. Teams often find themselves grappling with problems such as redundant code, inconsistent testing across modules, ambiguous dependencies, and the perennial debate between adopting a monorepo or maintaining separate repositories. These issues frequently translate into manual, time-consuming processes within CI/CD pipelines, from repeatedly validating numerous modules to painstakingly figuring out which infrastructure components a code change impacts. This article delves into Nx, an advanced build system, as a potent solution to these common Terraform management woes, offering a highly efficient framework for handling modules within a monorepo structure. For those keen to see these concepts in action, a comprehensive demo repository is available.

The Inherent Difficulties of Scaling Terraform Modules

Both multi-repository and monorepo strategies come with their own set of complexities when it comes to managing Terraform modules:

The Multi-Repo Predicament

While seemingly organized at first glance, with each module enjoying its own versioning and CI/CD pipeline, this approach quickly descends into “versioning hell.” When Module A relies on Module B, managing version pins becomes a delicate and often frustrating task. Updating one module necessitates careful updates, testing, and releases of its dependents, leading to cumbersome coordination across multiple repositories, each potentially with different CI configurations, testing methodologies, or even tool versions like tflint or terraform-docs.

Monorepo Challenges (Without Intelligent Tooling)

Adopting a monorepo can alleviate some versioning issues but introduces new ones. Without smart build systems, CI pipelines often run tests on all modules, regardless of whether they were affected by a change, leading to bloated build times. Tracking inter-module dependencies becomes a manual nightmare, and orchestrating tasks like terraform fmt across dozens of directories turns into a tedious script-writing exercise, severely degrading the developer experience.

Why Nx Transforms Terraform Module Management

Nx, a smart build system originally popular in JavaScript/TypeScript circles, is fundamentally language-agnostic. It provides several core features that are perfectly aligned with the needs of managing large-scale Terraform modules:

1. Intelligent Task Orchestration

Nx constructs and understands your project’s dependency graph. This allows it to:

  • Execute tasks only on affected projects, determined by your Git changes.
  • Run tasks in the correct order based on their dependencies.
  • Execute independent tasks in parallel, significantly speeding up workflows.

For Terraform, this means running terraform validate only on the modules that were changed and their direct or indirect dependents, rather than the entire monorepo.

2. Dependency Graph Visualization

A simple nx graph command generates an interactive visual representation of how your modules interconnect. This feature is invaluable for:

  • Onboarding new team members.
  • Planning complex refactors.
  • Understanding the potential “blast radius” of changes.
  • Identifying and resolving circular dependencies.

3. Code Generation

Nx generators facilitate the scaffolding of new modules with consistent directory structures, pre-configured project.json files, and even initial test and documentation setups. This allows teams to create new Terraform modules with a single command, enforcing standardization from the outset.

4. Consistent Tooling Across Projects

With Nx, tasks can be defined once and then inherited across all modules. This ensures that every module benefits from consistent formatting (terraform fmt), validation (terraform validate), linting (tflint), and documentation generation (terraform-docs) without the need to duplicate configuration files everywhere.

Crucially, Nx doesn’t dictate how you write your Terraform code; rather, it elevates how you manage your Terraform modules at scale, making development more streamlined and efficient.

Establishing an Nx Workspace for Terraform

Let’s outline the practical steps to set up an Nx workspace tailored for Terraform modules:

Workspace Initialization

Begin by creating a new Nx workspace using the “npm” preset, as we primarily need Nx’s task orchestration capabilities rather than a specific JavaScript application framework:

npx create-nx-workspace@latest terraform-modules --preset=npm
cd terraform-modules

Recommended Workspace Structure

A logical structure for organizing Terraform modules within an Nx monorepo typically looks like this:

terraform-modules/
├── nx.json
├── package.json
├── modules/
│   ├── scw-vpc/
│   │   ├── project.json
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   ├── outputs.tf
│   │   └── README.md
│   ├── scw-k8s/
│   │   ├── project.json
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   ├── outputs.tf
│   │   └── README.md
│   └── scw-database/
│       ├── project.json
│       └── ...
└── tools/
    └── scripts/

Each Terraform module resides in its own subdirectory under modules/ and contains a project.json file, which is where its Nx tasks are defined.

Configuring Nx for Terraform Projects

The project.json file is central to Nx’s functionality. Here’s an example for a module named scw-vpc:

{
  "name": "scw-vpc",
  "$schema": "../../node_modules/nx/schemas/project-schema.json",
  "projectType": "library",
  "sourceRoot": "modules/scw-vpc",
  "targets": {
    "fmt": {
      "executor": "nx:run-commands",
      "options": {
        "command": "terraform fmt -check",
        "cwd": "modules/scw-vpc"
      }
    },
    "fmt-fix": {
      "executor": "nx:run-commands",
      "options": {
        "command": "terraform fmt",
        "cwd": "modules/scw-vpc"
      }
    },
    "validate": {
      "executor": "nx:run-commands",
      "options": {
        "commands": ["terraform init -backend=false", "terraform validate"],
        "cwd": "modules/scw-vpc",
        "parallel": false
      }
    },
    "lint": {
      "executor": "nx:run-commands",
      "options": {
        "command": "tflint",
        "cwd": "modules/scw-vpc"
      }
    },
    "docs": {
      "executor": "nx:run-commands",
      "options": {
        "command": "terraform-docs markdown . > README.md",
        "cwd": "modules/scw-vpc"
      }
    }
  },
  "tags": ["type:terraform", "cloud:scaleway", "layer:network"]
}

The nx:run-commands executor is versatile, allowing you to run any shell command, which is perfect for integrating Terraform CLI commands. With this setup, you can then execute commands like:

nx fmt scw-vpc          # Check formatting for scw-vpc
nx validate scw-vpc     # Validate configuration for scw-vpc
nx lint scw-vpc         # Run tflint for scw-vpc
nx run-many -t validate # Run validation on all modules

Managing Dependencies Among Terraform Modules

One of Nx’s most compelling features is its understanding of project dependencies. However, since Terraform modules don’t use explicit import statements like some programming languages, Nx needs a little help to identify these relationships.

Implicit Dependencies

Nx can infer dependencies by analyzing your Terraform code. When one module references another using a relative path in its source attribute (e.g., source = "../scw-vpc"), Nx can detect this relationship. These implicit dependencies can be configured in your root nx.json file.

Explicit Dependencies

For more granular control and clarity, you can explicitly declare dependencies within a module’s project.json file. For example, if scw-k8s relies on scw-vpc:

{
  "name": "scw-k8s",
  "implicitDependencies": ["scw-vpc"],
  "targets": {
    // ...
  }
}

This explicit declaration informs Nx that scw-k8s depends on scw-vpc. Consequently, when you run nx validate scw-k8s, Nx will automatically validate scw-vpc first, then scw-k8s. More importantly, if you change scw-vpc, running nx affected -t validate will correctly identify and validate both scw-vpc and scw-k8s.

Visualizing the Graph

The nx graph command is invaluable for gaining a visual understanding of your entire module ecosystem. It opens an interactive browser view, displaying all your modules and their relationships, which is incredibly useful for new team members, planning refactors, and assessing the impact of changes.

Constructing a Task Pipeline

Nx truly shines when you define task pipelines that automatically execute in the correct order. By configuring targetDefaults in your nx.json, you can establish a robust workflow:

{
  "targetDefaults": {
    "fmt": {
      "dependsOn": []
    },
    "validate": {
      "dependsOn": ["^validate", "fmt"]
    },
    "lint": {
      "dependsOn": ["validate"]
    },
    "security": {
      "dependsOn": ["lint"]
    }
  }
}

The ^ prefix here signifies that a task should first run on the dependencies of a project. For instance, running nx security scw-k8s will trigger a sequence where Nx first validates all modules that scw-k8s depends on, then formats scw-k8s, validates it, lints it, and finally runs security scans—all automatically and in parallel where possible.

Common Targets

A comprehensive project.json typically includes targets for formatting (fmt, fmt-fix), validation (validate), linting (lint with tflint), security scanning (security with checkov), and documentation generation (docs with terraform-docs).

Executing Tasks Across Multiple Projects

Nx provides powerful commands to run tasks efficiently:

# Run fmt on all modules
nx run-many -t fmt

# Run affected validations and linting based on git changes
nx affected -t validate,lint

# Run tasks in a specific order across all modules
nx run-many -t fmt,validate,lint,security

# Run tasks on modules with specific tags
nx run-many -t validate --projects=tag:cloud:scaleway

Automated Code Generation and Scaffolding

Manually creating project.json files and initial Terraform boilerplate for every new module is tedious and prone to inconsistencies. Nx generators solve this by scaffolding consistent module structures with a single command.

Crafting a Custom Generator

You can create a custom generator (e.g., in tools/generators/terraform-module/index.js) that uses Nx’s devkit to generate files from templates and update the workspace configuration, including adding standard targets and tags to the new module’s project.json.

Utilizing the Generator

Once created, new modules can be consistently generated:

nx g @nx/workspace:workspace-generator terraform-module \
  --name=scw-function \
  --cloud=scaleway \
  --layer=compute

# This command creates a new module with the defined structure, project.json, and initial Terraform files.

This ensures every new module starts with the same foundational structure, targets, and tags, eliminating the need for copy-pasting and manual configuration.

Comprehensive Testing Strategies

Thorough testing of infrastructure code is paramount but often neglected. Nx facilitates building a robust testing pipeline that operates efficiently across all your modules.

Level 1: Static Analysis

  • terraform fmt & validate: Essential for basic syntax and semantic validation.
  • tflint: Catches common mistakes and enforces best practices, improving code quality.
  • checkov: Performs critical security and compliance scanning, identifying potential vulnerabilities.

Orchestrating Static Analysis with Nx

The real advantage emerges when Nx’s dependency graph integrates with your validation pipeline:

# Validate only modules affected by your changes
nx affected -t validate,lint --base=main

# Validate a module and all its dependencies
nx validate scw-k8s --with-deps

# Run security scans in parallel for independent modules
nx run-many -t security --parallel=3

# Execute full quality checks on affected modules
nx affected -t fmt,validate,lint,security --base=main

This intelligent orchestration can dramatically reduce CI times, from hours to mere minutes for large infrastructure repositories.

Seamless CI/CD Integration

Nx’s capabilities truly shine in CI/CD environments. Instead of running all checks on every module, Nx enables you to execute only what’s necessary.

GitHub Actions Example

A typical GitHub Actions workflow leveraging Nx would include steps to:

  • Checkout code with `fetch-depth: 0` (crucial for nx affected).
  • Set up Node.js and Terraform.
  • Install project dependencies and `tflint`.
  • Derive SHAs for nx affected commands using nrwl/nx-set-shas@v3.
  • Run affected format checks, validations, linting, and security scans using npx nx affected -t <target> --base=$NX_BASE --head=$NX_HEAD.

This approach ensures that only the modules impacted by a change are processed, leading to significantly faster CI feedback loops.

Benefits in CI/CD

  • Targeted Checks: Only affected modules are checked.
  • Parallel Execution: Independent tasks run concurrently.
  • Rapid Feedback: CI completion in seconds rather than minutes for most PRs.

In real-world scenarios, this can result in an 80%+ reduction in CI time.

Efficient Release Management with Nx

Nx’s built-in release system is a powerful, yet often underappreciated, feature for monorepos, proving invaluable for Terraform module versioning, changelog generation, and coordinating inter-module changes.

Initial Setup

Configure Nx Release in your nx.json, specifying project scope, the relationship between projects ("independent" is often preferred for Terraform modules), versioning strategies (e.g., based on Git tags), changelog generation settings, and Git integration for commits and tags.

Creating a Release

When modules are ready for release:

# See which modules have changed since the last release
nx release --dry-run

# Release only affected modules with automatic version bumping
nx release --projects=tag:cloud:scaleway

# Release a specific module with a specified version
nx release scw-vpc --specifier=1.2.0

Automated Semantic Versioning

Nx can automatically determine version bumps based on conventional commit messages:

  • fix: commits trigger patch versions.
  • feat: commits trigger minor versions.
  • BREAKING CHANGE: in the commit body triggers major versions.

Changelog Generation

Nx automatically generates well-formatted CHANGELOG.md files for each module, complete with breaking changes, features, bug fixes, and author information, eliminating manual updates.

Release Workflow in CI

Releases can be automated via CI/CD pipelines (e.g., GitHub Actions), configured to run npx nx release --skip-publish upon merges to main, handling version bumps, changelog updates, and Git tagging automatically.

Tagging Strategy and Module Consumption

Nx creates distinct Git tags for each module release (e.g., [email protected]). This allows external consumers to reference specific module versions directly in their Terraform configurations using Git URLs with references.

Independent vs. Fixed Versioning

Nx supports both independent versioning (each module has its own version, bumping only when changed) and fixed versioning (all modules share and bump the same version). Independent versioning is generally recommended for loosely coupled Terraform modules.

Benefits of Nx Release

The advantages include automatic versioning, generated changelogs, consistent Git tagging, affected-aware releases, and even automated GitHub release creation, significantly simplifying the management of numerous Terraform modules.

A Real-World Scenario

Consider a SaaS company managing its Scaleway infrastructure within an Nx monorepo. They have several interconnected modules, such as scw-vpc, scw-k8s (dependent on VPC), scw-database (dependent on VPC), and scw-object-storage (independent).

The Dependency Graph

The dependencies might look like this:

scw-vpc
  ├── scw-k8s
  │   ├── scw-loadbalancer
  │   └── scw-monitoring
  ├── scw-database
  └── scw-registry

scw-object-storage (independent)

Running nx graph would visualize this complex network.

Scenario: Updating the VPC Module

If a developer adds a new subnet to scw-vpc, Nx’s nx show projects --affected command will identify not only scw-vpc but also all its downstream dependents (e.g., scw-k8s, scw-database, scw-registry, etc.). When CI runs nx affected -t validate,lint, only these affected modules are processed, while the independent scw-object-storage module is entirely skipped.

Scenario: Adding a Feature to Monitoring

If only scw-monitoring is updated, nx show projects --affected will correctly identify only scw-monitoring. Subsequently, the CI pipeline will validate and lint only this single module, leading to massive time savings.

The Impact

Before Nx, every pull request would trigger checks on all 7+ modules, taking considerable time. With Nx, small changes result in checks on only 1-2 modules (minutes), and even core VPC changes only affect a subset of modules (still significantly faster). This provides clear visibility into impact and boosts developer productivity.

Key Best Practices

Based on practical experience, here are crucial best practices for using Nx with Terraform:

1. Leverage Meaningful Tags

Strategic tagging in project.json (e.g., type:terraform, cloud:scaleway, layer:network, team:platform) allows for powerful filtering and targeted command execution across your monorepo.

2. Maintain Small and Focused Modules

Design each module to perform a single, well-defined function. This enhances reusability, simplifies testing, and reduces complexity.

3. Thoughtful Use of Target Dependencies

Define clear task pipelines in nx.json using targetDefaults and dependsOn to ensure tasks execute in the correct logical order (e.g., formatting before validation).

4. Automate Documentation with terraform-docs

Integrate terraform-docs into your Nx targets to automatically generate and update module documentation (e.g., README.md files), ensuring consistency and accuracy.

5. Implement Pre-commit Hooks

Utilize tools like Husky to create pre-commit hooks that run quick Nx affected checks (e.g., fmt-fix and validate) before code is committed, catching issues early.

Limitations and Considerations

While Nx is a powerful tool, it’s not a panacea. Here are some honest tradeoffs to consider:

Learning Curve

Teams will need to invest time in understanding Nx concepts (projects, targets, affected commands) and basic Node.js/npm, even if they aren’t primarily JavaScript developers. Starting small can help mitigate this.

Node.js Dependency

Introducing Node.js into infrastructure workflows might seem unusual to some teams. However, Node.js is ubiquitous, lightweight, and likely already present in most CI environments, making this a minor concern against its benefits.

Unchanged State Management

Nx solely focuses on workspace organization and task orchestration. It does not address Terraform’s state files, state locking, remote backends, or workspace management, which still require careful handling according to Terraform best practices.

Not Ideal for Small Projects

For projects with only one to three Terraform modules that rarely change, the overhead of setting up and maintaining Nx might outweigh its benefits. Nx is most impactful for larger, more dynamic monorepos.

Module Source References

Modules within the monorepo use relative paths. For external consumption, you’ll need to publish to a module registry or use Git tags with specific references to ensure stability.

When NOT to Use This Approach

  • Single-module projects: Plain Terraform suffices.
  • Completely independent modules: Separate repositories might be simpler if modules never interact.
  • Teams resistant to change: Cultural fit and willingness to adopt new tooling are paramount.

It’s crucial to be pragmatic: ensure you have the problems Nx solves before adopting it.

Conclusion

Managing Terraform modules at scale doesn’t have to be a source of constant frustration. Nx effectively bridges the gap between proven monorepo best practices from the software development world and the unique demands of infrastructure as code. It offers:

  • Intelligent task orchestration, running only what’s necessary.
  • Deep dependency awareness, automatically understanding module relationships.
  • Significantly faster CI/CD, often yielding 80%+ time savings.
  • Enhanced developer experience through consistent tooling, code generation, and clear workflows.

While the initial setup and learning curve require an investment, the return on investment for teams managing five or more dynamic Terraform modules is substantial. Starting with a small set of modules to prove the concept and measure its impact is a recommended approach. As the landscape of infrastructure management evolves, smart, graph-aware tooling like Nx brings us closer to a future of more efficient and confident IaC development.

Resources

Demo Repository

  • nx-terraform-demo – A complete, functional example showcasing 7 Scaleway Terraform modules managed with Nx.

Nx Documentation

Terraform Tooling

  • terraform-docs – Automated documentation generation for Terraform modules.
  • tflint – A pluggable linter for Terraform.
  • checkov – Static analysis tool for IaC security and compliance.

Scaleway Provider

Further Reading

Have you integrated Nx into your Terraform workflows? Share your experiences and insights! Connect with me on Bluesky or GitHub.

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