Twelve-Factor Apps in Kubernetes

In this post, we’ll talk about how Kubernetes can help in implementing the application design standards of the Twelve-Factor App methodology.

A major area of focus for software developers is how to design applications that are efficient, robust, and easy to maintain. The techniques and tools used to create such applications have evolved with the introduction of modern platforms such as the cloud. Modern applications need to be portable, scale well, and withstand failures.

Standards and best practices serve as a general guide toward designing applications well. One set of standards for modern, cloud-based applications is known as the Twelve-Factor App. 

The Twelve-Factor App is a set of a dozen best practices for application design. These were created by the developers of the Heroku cloud platform, and these best practices are popular among application developers today for improving application design.

When we talk about application design, we don’t just mean the look and feel of the user interface. Application design is about how the application is built behind the scenes — the underlying architecture of the application. Well-designed apps tend to be more reliable and easier to maintain.

Twelve-Factor Apps are designed to run well on modern platforms, taking full advantage of everything these platforms have to offer. However, the platforms themselves can also serve to help implement best practices such as those outlined in the Twelve-Factor App design methodology.

As containers have grown in popularity as a method for running applications, Kubernetes has emerged as one of the most widely used platforms for managing containers. Part of what makes Kubernetes a great tool for container orchestration is that it is built with best practices for application design in mind.

Coupled with container technology, Kubernetes includes a variety of features that can actually help you implement best practices such as those put forward by the Twelve-Factor App methodology.

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Here are some examples here of how Kubernetes can help you implement the standards of a Twelve-Factor App.

One of the twelve factors deals with the concept of configurability and configuration management. 

In a Twelve-Factor App, behaviors that may differ between environments are not controlled through the code itself, but through external configuration. So, a configuration value that can differ between a development environment and a production environment is supplied outside of the code or executable itself.

Kubernetes supports this functionality using ConfigMaps and Secrets. Configuration data can be maintained using these objects, and then passed to the application at runtime in the form of environment variables or configuration files. You can even maintain configurations for multiple environments (i.e. dev and prod) in the same cluster.

Another of the twelve factors concerns interchangeable backing services. 

Twelve-Factor Apps that rely on backing services such as web services or databases can easily switch between multiple implementations of the backing service, such as a local development database and a production database.

In Kubernetes, Services provide a layer of abstraction over backing services both inside and outside the cluster. They can be used to wire the application to different backing service implementations without the need for the application itself to be aware of which implementation it is using.

In a Twelve-Factor App, development environments are as similar as possible to production environments. This concept is known as dev/prod parity. This minimizes the deployment issues that can often arise when the development or testing environment differs significantly from production.

In Kubernetes, you can use Namespaces to host multiple more-or-less identical environments within the same cluster. 

Each Namespace can include its own copy of the application, including all of its backing services and infrastructure. This simplifies dev/prod parity by allowing you to host both in the same environment without interference between the two.

These are just a few examples of the ways Kubernetes can help you implement modern best practices such as those outlined in the Twelve-Factor App methodology.

If you want to learn more about how you implement all twelve factors in Kubernetes, check out my new course Designing Applications for Kubernetes.

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In this course, we'll walk through the 12 factors and how to implement each of these factors in a K8s environment. You’ll also be challenged by Hands-on Labs that will task you with demonstrating a mix of skills to combine multiple factors at once. (Already logged in to ACG? Get started with this course here.)

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