Kubernetes

Based on the official Kubernetes website definition:

Kubernetes (K8s) is an open-source system for automating deployment, scaling, and management of containerized applications.

However, I don't think this description honors what Kubernetes really does best: reconcile resources.

Funnily enough, the fact that Kubernetes is able to deploy and manage conterinerized applications is primarily because of how the reconciliation of resources happen.

Application and environment

Usually, when we had to deploy an application we had constant friction between the application developers and the operations teams -- the ones that will ultimately be putting the application into production and maintain its day-to-day operation.

Let's take a step back and see what each step on this story brought us.

Containerization

By being able to easily create a "snapshot" of our application and all its dependencies, we were able to greatly reduce the friction between our application and the system it's running on. As developers, we now have much greater control on the environment our application is running on.

Of course, this does not mean that we are the sole responsibles of this, but now we have more certainty of what is the environment our application runs on.

Still, something is missing: how our application is exposed to the world. There is still a gap here: we provide the snapshot of our application, but how it's exposed and operated is not up to us.

Infrastructure as config

Kubernetes is usually referred to as Infrastructure as code, but in this sense I prefer to call it Infrastructure as config. Now, with Kubernetes, we have the ability to track the way our application is deployed and managed:

  • What versions of every component of our applications are bundled together?
  • Application secrets
  • Configuration
  • Storage used by the application
  • How the application is exposed
  • Security
    • What can this application know about the platform?
    • What permissions have this application when running, at the node level?

In general, we can see that while containerizing made our snapshot of our application broader, Kubernetes also includes how this application is operated in its snapshot. We now have a complete, reproducible way of deploying an exact version of our application, including how it is operated.