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Leveraging Infrastructure as Code (IaC) Modules for Efficiency and Reliability

By understanding the different levels of abstraction in IaC and how modules fit into the broader picture, you can improve governance, documentation, MTTR (mean time to recovery), enhance consistency, and increase the reliability of your infrastructure.

Understanding IaC Abstraction Levels​

Gruntwork uses a four-layer system for describing infrastructure --

Direct Infrastructure (Lowest-Level): This is your actual deployed infrastructure, such as servers, networks, and databases.

Resource-Level IaC (Mid-Level): OpenTofu provides wrappers around cloud provider APIs and represents objects in those APIs as resources. Using OpenTofu you can define individual infrastructure resources (e.g., servers, networks, databases) in code. This improves consistency and enables version control, but managing complex deployments and establishing consistency and governance can still be challenging given that every time you deploy infrastructure you have to re-specify each resource and all its arguments.

Module-Level IaC (High-Level): Modules encapsulate multiple resources into reusable building blocks. For example, a module could define a web server with a load balancer, database, and security groups. Modules increase efficiency, reduce complexity, and promote best practices. Modules provide the opportunity for core teams to codify best practices and business requirements.

Service-Level IaC (Highest-Level): At this level, you compose modules to create complete, deployable architectures, such as a multi-tier application or a data pipeline. This allows a platform team to even further codify architectures, opinions, compliance and security structures that are reusable across the enterprise.

Diagram showing IaC Module Hierarchy

Benefits of IaC Modules​

  • Increased Efficiency: Modules eliminate the need to write repetitive code, accelerating infrastructure deployments.
  • Reduced Errors: Pre-defined and tested modules minimize the risk of configuration errors and ensure consistency.
  • Improved Collaboration: Modules promote code reuse and shared understanding across teams.
  • Enhanced Compliance: Modules can incorporate security and compliance best practices, ensuring your infrastructure adheres to standards.
  • Simplified Documentation: Modules serve as self-documenting building blocks, clearly defining infrastructure components and their relationships. Modules also regularly ship with separate documentation and examples to further explain, justify and demonstrate their use.
  • Faster Recovery: Modules stored in version control enable rapid redeployment of infrastructure from code, allowing you to quickly find and revert any mistakes from Click-ops, manual changes or other bad deployments.
  • Faster Scaling: Modules allow you to scale infrastructure quickly by reusing existing components to deploy additional copies or expand into new regions, shared-fate zones, or data centers.

IaC Modules and Documentation​

While IaC code itself serves as a form of documentation, it's crucial to supplement it with clear and concise explanations.

  • Well-commented Code: Use comments to explain the purpose and functionality of modules and resources within your IaC code.
  • Module Documentation: Create dedicated documentation for each module, including:
    • Purpose and functionality
    • Input variables and outputs
  • Usage examples: Provide examples of how to use the module in different scenarios with reasonable input variables.
  • Design decisions and rationale: Often there's more than one way to architect a solution to a problem, justify why this approach was taken and the tradeoffs it optimizes for.

IaC Modules and Disaster Recovery​

IaC modules significantly improve disaster recovery capabilities:

  • Rapid Redeployment: Redeploy infrastructure quickly from code in case of failures.
  • Infrastructure as Code: Maintain a version-controlled source of truth for your infrastructure, allowing you to see what changes were made when, and by whom, and roll back in an automated, efficient manner.
  • Consistent Environments: Recreate identical environments in different regions for redundancy.
  • Drift Detection and Correction: Identify and correct configuration drift by comparing the actual infrastructure to the defined IaC code.