MSDN Documentation

Infrastructure as Code Best Practices

Introduction

Infrastructure as Code (IaC) is the practice of managing and provisioning IT infrastructure through machine-readable definition files, rather than through physical hardware configuration or interactive configuration tools. This approach brings the benefits of software development, such as version control, testing, and automation, to infrastructure management.

Implementing IaC effectively requires adherence to best practices to ensure consistency, reliability, and scalability of your cloud or on-premises environments. This document outlines key best practices for successful Infrastructure as Code adoption.

Version Control Everything

Treat your infrastructure code as you would any other application code. Store all configuration files, scripts, and definitions in a version control system like Git. This provides:

  • History and Auditing: Track every change, who made it, and when.
  • Rollback Capabilities: Easily revert to a previous known good state if issues arise.
  • Collaboration: Enable multiple team members to work on infrastructure concurrently using branching and merging strategies.
  • CI/CD Integration: Form the foundation for automated build, test, and deployment pipelines.

Use clear commit messages and a well-defined branching strategy (e.g., Gitflow) to manage changes.

Modularity and Reusability

Break down your infrastructure into smaller, reusable components or modules. This enhances maintainability and reduces duplication. For example, a common pattern for defining a virtual machine might be encapsulated in a module that can be instantiated multiple times with different parameters.

Benefits include:

  • DRY Principle (Don't Repeat Yourself): Avoid writing the same code multiple times.
  • Consistency: Ensure that identical resources are configured identically.
  • Maintainability: Update a module once, and the change propagates to all instances.

Leverage the module features provided by your IaC tool (e.g., Terraform Modules, CloudFormation Nested Stacks, Ansible Roles).

Idempotency is Key

An idempotent operation is one that can be applied multiple times without changing the result beyond the initial application. In IaC, this means that running your infrastructure code multiple times should result in the same desired state without unintended side effects.

Most modern IaC tools strive for idempotency. However, it's crucial to:

  • Understand how your chosen tool handles idempotency.
  • Write your code in an idempotent manner, especially for custom scripts or complex configurations.
  • Avoid manual changes to the infrastructure that are not reflected in the code, as these break idempotency.

An example of idempotency in action: if you apply a configuration that ensures a service is running, running the same configuration again won't stop and restart the service if it's already running; it will simply confirm that the desired state is met.

Testing Your Infrastructure

Just like application code, infrastructure code needs to be tested to ensure correctness and prevent regressions.

Types of testing include:

  • Linting: Static analysis of code for syntax errors and style violations.
  • Syntax Checking: Validating the syntax of your IaC files.
  • Unit Testing: Testing individual modules or components in isolation.
  • Integration Testing: Verifying that different components work together correctly.
  • End-to-End Testing: Deploying a complete environment and testing its functionality.

Tools like Terratest, Kitchen-Terraform, and infrastructure testing frameworks can help automate this process.

Automate Everything

The core benefit of IaC is automation. Aim to automate as much of the infrastructure lifecycle as possible:

  • Provisioning: Automatically create new environments.
  • Configuration: Automatically configure servers and services.
  • Updates and Patching: Automate the application of updates and security patches.
  • Decommissioning: Automatically tear down environments when they are no longer needed.

Integrate your IaC workflows into a CI/CD pipeline for continuous delivery of infrastructure changes.

Document Your Code

Clear documentation is essential for any code, and IaC is no exception. Document:

  • Purpose of modules and resources.
  • Input variables and their expected values.
  • Output values and what they represent.
  • Assumptions and dependencies.
  • Deployment procedures.

Use README files within your module directories and leverage documentation generation tools where possible.

Security Considerations

Security should be a first-class citizen in your IaC practices:

  • Least Privilege: Ensure that your IaC tools and service principals have only the necessary permissions to perform their tasks.
  • Secrets Management: Never hardcode sensitive information (passwords, API keys) directly in your code. Use secure secrets management solutions (e.g., Azure Key Vault, AWS Secrets Manager, HashiCorp Vault).
  • Network Security: Define network security groups, firewalls, and access controls as part of your IaC.
  • Auditing: Ensure that changes to your infrastructure are auditable.
  • Regularly review and update security configurations.
Tip: Integrate security scanning tools into your CI/CD pipeline to detect vulnerabilities in your infrastructure code before deployment.

Conclusion

Adopting Infrastructure as Code best practices can significantly improve the efficiency, reliability, and security of your IT operations. By embracing version control, modularity, idempotency, thorough testing, and automation, you can build and manage resilient and scalable infrastructure environments.