What Is Infrastructure as Code?

Infrastructure as code (IaC) is a methodology used to automate the management and provisioning of computing infrastructure through machine-readable definition files, rather than relying on physical hardware configuration or interactive configuration tools. IaC approaches infrastructure setup as a software development task, enabling automation, versioning, reproducibility, and testing. This guide will walk through some foundational concepts of IaC.

Before delving deeper into IaC, it’s essential to understand its significance.

Traditional IT setups often involve manual processes for provisioning new infrastructure, which can be time-consuming and prone to errors and inconsistencies. When building applications in the cloud, teams often start in a cloud provider’s console, creating resources like Lambda functions, selecting triggers, and connecting services directly from the user interface (UI). Problems can arise when there’s a need to move resources between accounts or environments, or replicate what’s been done in the console. IaC eliminates these challenges.

IaC addresses these issues by replacing manual tasks with scripts and automation, thereby reducing errors, improving efficiency, and enhancing repeatability. The primary benefit is that infrastructure can be set up and scaled with less time, fewer resources, and greater consistency. By automating resource provisioning, IaC allows for versioning of infrastructure similarly to source code, applying the same principles of application development to infrastructure management. Instead of manually configuring services in a console, all configurations are listed in a single place — a configuration file.

Why is building infrastructure with code superior to using a UI? Several key reasons stand out:

1. Consistency across environments: By using the same configuration files across environments, IaC ensures consistency, eliminating disparities between different setups. There is a single source of truth — the configuration file — which prevents surprises during deployment to different environments.
2. Streamlined onboarding process: When a new developer joins a team, the setup process can be simplified. Instead of navigating through extensive documentation, the new team member is provided with the configuration file, making the setup process efficient and straightforward.
3. Elimination of configuration drift: Configuration drift occurs when environments differ due to manual changes made during incident management or other processes. With IaC, one central authority — the configuration file — keeps all environments in sync, preventing such drift.
4. Risk mitigation: Manually provisioning infrastructure is risky, error-prone, and often dependent on a single individual. IaC mitigates this risk by turning infrastructure into reproducible code blocks stored in a version-controlled repository, making it accessible and visible to all team members.

These benefits illustrate why IaC is gaining traction and becoming an industry standard for managing infrastructure. It streamlines processes, reduces errors, and facilitates team collaboration, making it a smart choice for any development team.

Configuration files are central to IaC. These files are scripted instructions that define and control the behavior of systems. They can be written in various languages or formats, including YAML, JSON, or domain-specific languages (DSLs) like HashiCorp Configuration Language (HCL) used in Terraform.

A configuration file in IaC serves as the blueprint for infrastructure, outlining exactly how every component, including servers, databases, and networks, should be set up. The structure of configuration files may differ depending on the IaC tool used, but generally, they include four key elements:

1. Resources: This critical part of the configuration file defines the infrastructure components needed, such as virtual machines, databases, and networks, along with their specific attributes.
2. Variables: User-defined values can be used across the configuration file, allowing for more dynamic and flexible configurations without changing the resource definitions.
3. Outputs: These values are returned after the configuration file is executed and are useful for extracting information about the created infrastructure, such as IP addresses and identifiers.
4. Providers: In some IaC tools like Terraform, providers specify the services or platforms where resources will be managed, such as AWS, GCP, or Azure.

Configuration files enable infrastructure to be treated as code, allowing for versioning, deployment, and rollback, just as with regular code. This process ensures infrastructure is managed in a safe, consistent, and repeatable way.

Adopting IaC in an organization can be approached differently depending on the starting point. Let’s say you’re using a tool like Terraform. On Day 1, when no infrastructure exists, the configuration file describes the desired setup, and the IaC tool creates the necessary resources. After the first day, where existing infrastructure is present, IaC helps manage and evolve the infrastructure as new components and complexities are added.

Over time, infrastructure will expand and evolve. On Day N, when it’s time to decommission certain resources, they can be removed from the configuration file, reflecting the changes in the actual infrastructure.

One of the key advantages of using IaC is the ability to continuously use the same workflow — write, plan, and apply — to evolve the infrastructure. Separate processes for each stage of development are unnecessary, making IaC a powerful tool for managing infrastructure throughout its lifecycle.

In conclusion, IaC streamlines infrastructure management through automation, enhances consistency across environments, and reduces the potential for human error. The core workflow ensures that the infrastructure is always evolving, making IaC an essential practice for modern development teams.