Version management in Terraform can be tricky. Here are seven important practices you should adopt when provisioning infrastructure using Terraform. 

As the cornerstone of modern infrastructure as code (IaC), Terraform provides many benefits to DevOps teams looking to maximize the flexibility and scalability of their infrastructure through automation. While many have abandoned the service following its switch from open source to a business license, the Terraform Cloud service remains a staple of DevOps teams.

One factor that it’s important to think about when starting to use Terraform is how pivotal version management is to ensure the consistency and stability of infrastructure deployments. As with any tech solution, whenever Terraform releases a new version, there have been known to be issues with back-compatibility. New functionalities are added, old ones removed, the way the system’s code arguments work might change, and so forth, causing unexpected issues to the infrastructure you manage with it.

This article will cover seven important practices you should adopt when it comes to managing what version of Terraform you’re running to provision infrastructure.

1.  Use version constraints

Version constraint is a Terraform feature that lets you specify which versions of Terraform, providers, or modules are compatible with your configurations. You can list a range of accepted versions, and anything outside of this range will be rejected during initialization.

The benefit of applying version constraints is to prevent breaking changes in resources (modifications that are incompatible with previous versions) to negatively impact your configuration.

Version constraints are applied with a string containing one or more conditions. This includes the version number, and an operator to indicate equal, greater than, etc.

For example, if you want to specify a version constraint for your Terraform AWS provider, you would use something like:

version = "~> 3.0"

Here, the “~>” operator allows compatibility with all minor versions of 3.x, but prevents automatic upgrades to 4.x. So there is a lot of flexibility with how you use these constraints to fit your configuration.

2.  Automate version management with tfenv

In some cases, instead of limiting everything to a particular version, you might need to juggle between several versions, particularly if you are using multiple Terraform deployments for different projects.

In that case, you might want to use a tool called tfenv. This tool is a version manager for Terraform, and it allows users to switch seamlessly between different versions of Terraform based on project requirements. The tool can be installed with the following command:

brew install tfenv

You can then install the specific versions you need and apply the “use” parameter to switch to the desired version, making it active for your current session or globally for all projects.

The tool is developed by Terraform parent company Hashicorp itself, so you can expect active support and an intuitive integration with your projects.

3.  Standardize versions across teams

When working in a large team, it’s important that all team members use the same Terraform version to maintain consistency and minimize errors caused by version mismatches.

To enforce version consistency, you can create a .terraform-version file in the project directory. This file can specify the exact Terraform version required for a given project.

This is where tfenv can come into play again, to automatically read the file and switch to the correct version.

CI/CD pipelines can also be configured to ensure the correct Terraform version is used during automated workflows. The pipeline should be configured to fail if the required version is not detected, so as to prevent deployment with an incompatible version.

4.  Pin module and provider versions

Never forget to explicitly specify the version of a provider, module, or Terraform itself in your configuration files.

Without pinning the desired version, Terraform may automatically default to the latest version available. This may sound like a good thing, but it can easily lead to breaking changes, incompatibility issues, or deployment failures.

You never really know how your configuration will react to even the slightest changes in newer versions. That’s why it’s best to first ensure the stability and predictability of your infrastructure, and you can then figure out ways to safely test and adopt newer versions.

5.  Test new versions in isolated environments

If you get to the point where you want to upgrade to a newer version to enjoy the benefits that come with it – new features, improved performance, and bug fixes – you should never do so directly in a live environment.

Instead, test the new version in a controlled, isolated environment to see how it interacts with your existing configurations.

A lot of times, everything will work normally, but there will likely be cases where you need to do some troubleshooting, whether it’s adjusting your configurations or updating dependencies.

6.  Regularly audit and update versions

Auditing and regularly updating the versions of Terraform, modules, and providers is beneficial for two main reasons.

First, there is the security aspect. Older versions may have known vulnerabilities that put your entire infrastructure at risk. On top of that, using old versions means that you miss out on improvements in newer versions, which can sometimes be substantial.

Terraform Validator is an excellent tool for version auditing. You can use it to scan your configs for outdated syntax or best practices violations and detect resources that might be incompatible with newer versions.

Terraform Validator is deployed with the terraform validate command.

7.  Maintain a version history

All of these configuration changes, like version constraints or updates, should be meticulously tracked in a version history archive. This provides a clear record of when, what, and when changes were made, facilitating accountability and troubleshooting.

Git is a popular version control system that you can use for your Terraform configurations. To initialize a Git repository, use the git init command. You can then add files to the repository with:

git add (file_name).tf

Each commit should clearly describe the changes made. Avoid vague messages like "Updated files." Instead, write something meaningful, like "Added version constraint for Azure provider to prevent compatibility issues."

Conclusion

Version management in Terraform can be tricky, but with the right strategies and tools, it becomes a smooth and essential part of maintaining stable and reliable infrastructure.

Take the time to understand and implement these strategies into your workflow, and you will be close to mastering how to maintain consistency and leave the ghosts of compatibility issues in the past.

More Information

Complete Guide to Terraform Cloud Pricing 

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