Infrastructure as Code Concepts
External
Internal
Overview
Infrastructure is not something you build and forget, in requires constant change: fixing, updating and improving. Infrastructure as Code is a set of technology and engineering practices aimed at delivering change more frequently (or, some would say continuously), quickly and reliably, while improving the overall quality of the system at the same time. Trading speed for quality is a false dichotomy. Used correctly, Infrastructure as Code embeds speed, quality, reliability and compliance into the process of making changes. Changing infrastructure becomes safer. Infrastructure as Code is based on practices from software development, especially test driven development, continuous integration and continuous delivery.
The capability to make changes frequently and reliably is correlated with organizational success (Accelerate by Dr. Nicole Forsgren, Jez Humble and Gene Kim). Changes include adding new services, such as a new database, upgrades, increase of resources to keep up with load, change and tune underlying application runtimes for diagnosis and performance reasons, security patches. Stability comes from the capability of making changes fast and easy: unpatched systems are not stable, they are vulnerable. If you can't fix issues as soon as you discover them, the system is not stable. If you can't recovery from failure quickly, the system is not stable. If the changes you make involve considerable downtime, the system is not stable. If changes frequently fail, the system is not stable.
Core Practices
Define Everything as Code
Code can be versioned and compared, it can benefit from lessons learned in software design patterns, principles and techniques such as test driven development, continuous integration, continuous delivery or refactoring.
Continuously Test and Deliver
Continuously testing small pieces encourages a modular, loosely coupled design. It also helps you find problems sooner, then quickly iterated, fix and rebuild when. you find the problems, which yields better infrastructure.
Build Small, Simple, Loosely Coupled Pieces that Can Be Changed Independently
Microservices fall into this category.
Stack
Collection of infrastructure resources provisioned from cloud platforms.