Terraform Azure Compute Module

This Terraform module is crafted for Azure compute resources, showcasing best practices in version pinning and module release strategies during the IaC Best Practices Workshop.

Table of Contents

• Introduction
• Table of Contents
• About Version Pinning
• Version Pinning for Consumers
• Version Pinning for Developers
• Testing Configuration Stability

About Version Pinning

Terraform modules are an essential part of Infrastructure as Code (IaC) workflows. When using modules from external sources, it's crucial to manage versions to ensure the stability and predictability of your infrastructure.

In this workshop, we'll use the example of the terraform-azure-compute module to understand version pinning and its implications.

Module Without Version Pinning

Here's an example of using the terraform-azure-compute module without version pinning:

module "azure_compute" {
    source = "github.com/iac-best-practices-workshop/terraform-azure-compute"

    # Additional configuration...
}

In this scenario, we are not specifying a module version, which means we are using the latest available version. This approach may lead to unexpected changes if the module is updated.

Fixed Version Pinning

Fixed version pinning ensures that a specific module version is used. Here's an example of fixed version pinning:

module "azure_compute" {
    source = "github.com/iac-best-practices-workshop/terraform-azure-compute?ref=v1.0.0"

    # Additional configuration...
}

In this case, we are explicitly specifying the version of the module to use, ensuring stability. However, updates and improvements to the module may be missed.

Flexible Version Pinning

Flexible version pinning allows using the latest version within a specified range. Here's an example of flexible version pinning:

module "azure_compute" {
    source = "github.com/iac-best-practices-workshop/terraform-azure-compute?ref=v1.1.X-stable"

    # Additional configuration...
}

In this scenario, we use a version range (v1.1.X-stable) that allows us to receive bug fixes and minor updates while maintaining stability. However, major breaking changes should be avoided.

Implications

Version pinning has significant implications for Terraform configurations:

• Stability: Pinning to a specific version ensures configuration stability.
• Control: Fixed pinning provides precise control over the module version.
• Maintenance: Flexible pinning balances stability with the ability to receive updates.

Maturity Levels

Version pinning can be categorized into different maturity levels:

• None (No Pinning): No version specified, highest risk of unexpected changes.
• Fixed (Exact Pinning): A specific version is used, offering stability but may miss updates.
• Flexible (Range Pinning): A version range is specified, balancing stability with updates.

Version Pinning for Consumers

Project Cloning

Fork this project first.

Then, clone it to your space and navigate to the directory:

git clone git@github.com:{your-username}/terraform-version-pinning.git
cd terraform-version-pinning

Resource Provisioning with v1.0.0

Navigate to usage-v1.0.0:

cd usage-v1.0.0

main.tf here uses version v1.0.0:

module "compute-resources" {
  source = "github.com/iac-best-practices-workshow/terraform-azure-compute?ref=v1.0.0"
  # Additional configuration...
}

Run terraform init | plan | apply to set up the resources.

Resource Provisioning with v1.1.0

Switch to usage-v1.1.0:

cd ../usage-v1.1.0

This main.tf points to v1.1.0:

module "compute-resources" {
  source = "github.com/iac-best-practices-workshow/terraform-azure-compute?ref=v1.1.0"
  # Additional configuration...
}

Execute terraform init | plan | apply. Notice the VM now has two network interfaces.

Version Pinning for Developers

This section guides you through adding a resource to terraform-azure-compute and releasing a new version, demonstrating the robustness of version pinning.

Repository Cloning

If not already done, clone the repository:

git clone git@github.com:{your-username}/terraform-version-pinning.git
cd terraform-version-pinning

Module Modification

1. Edit main.tf in the terraform-azure-compute repository.
2. Introduce a new Azure resource:

resource "azurerm_virtual_machine" "additional_vm" {
    # Configuration details...
}

3. Commit and tag the new version:

git add .
git commit -m "Add new resource, update module version"
git tag v1.2.0
git push origin v1.2.0

Testing Configuration Stability

Verify that the v1.0.0 configurations remain unaffected by the new release:

1. Return to usage-v1.0.0 and run terraform plan.
2. Observe no changes due to version pinning.
3. Update usage-v1.0.0 to point to your project refv1.2.0 and observe the impacts:

module "compute-resources" {
  source = "github.com/{your-username}/terraform-azure-compute?ref=v1.2.0"
  # Additional configuration...
}

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Congratulations! You've mastered using version pinning to maintain stability in Terraform configurations as your module evolves, ensuring seamless experiences for your users.