I posted Terraform Intro and Key Concepts previously in this series and now I want to talk briefly about Terraform best practices and tools.

Best Practices:

Use Modules: Write reusable and modular code. Keep resource definitions simple by organizing common components into modules.

State Management: Use remote backends (like S3 with locking via DynamoDB) to store state securely and avoid conflicts when working in teams.

Version Control: Pin Terraform and provider versions in your code to avoid unintentional upgrades.

Use Workspaces for Environments: Isolate environments (e.g., dev, prod) using workspaces or separate state files to avoid accidental changes across them.

Plan Before Apply: Always view the terraform plan before applying changes to preview what will happen and catch potential issues early. You can run the terraform plan command but also terraform apply will show you a plan followed by an interactive prompt by default. You could avoid this interactive prompt by running terraform apply -auto-approve.

Tagging Resources: Always tag your resources with metadata like environment, owner, or purpose to improve tracking and management.

Automated Testing: Implement testing using tools like Terratest to verify your Terraform configurations.

Sensitive Data: Avoid hardcoding sensitive information in your Terraform code. Instead, use external tools like Vault or cloud-native secret managers.

Drift Management: You want to minimize drift – keep your environment as up-to-date with your Terraform code as possible. This means infrastructure managed by Terraform should not be updated by other means unless it cannot be avoided. And when you change Terraform code you should run a terraform plan and terraform apply as soon as possible so that your environments will match your Terraform code.

Tools to consider

I have only personally used Terragrunt and tflint but I have heard some of these others can be useful as well and all of them are actively maintained in 2024 and have at least some features available on a free, open source basis.

Terragrunt: A wrapper for Terraform that simplifies managing multiple environments and modules. It helps with DRY principles and managing state files.

tflint: A linter for Terraform that checks for errors and warns about best practices.

Terratest: validate that the infrastructure works correctly in that environment by making HTTP requests, API calls, SSH connections, etc

terraform-docs: Generates documentation for your Terraform modules, ensuring they’re well-documented.

infracost: Provides cost estimates for your infrastructure before applying changes, helping you understand and optimize costs.

Terrascan: Scans Terraform code for security vulnerabilities and policy violations.

Atlantis: Automates Terraform workflows via pull requests, making team collaboration easier.

tfsec: A static analysis tool to find security issues in your Terraform code.

Checkov: An infrastructure-as-code scanner that detects potential security misconfigurations.