Demystifying Kubernetes Operators

This article explores Kubernetes Operators, how they work, and the practical scenarios where they can make life easier for k8s application users.

What Are Kubernetes Operators?

Kubernetes Operators are basically applications that extend Kubernetes’ core functionality by leveraging native features — specifically, Custom Resource Definitions (CRDs) and Controllers. An Operator is software running within your Kubernetes cluster that interacts with the Kubernetes API to handle certain tasks automatically.

At a high level, an Operator monitors the state of custom resources and takes actions (via its controller) to make sure the real-world cluster situation lines up with what users specify when creating those custom resources.

Custom Resources and CRDs

A Custom Resource (CR) is a way to expand Kubernetes so you can manage and define objects that aren’t included by default. You define these new objects via Custom Resource Definitions (CRDs), which serve as your blueprint or schema for those custom resources.

Let’s imagine you want to offer a custom database service (let’s call it NewDB) within your cluster. Without any Operator magic, a user might have to manually configure everything. However, with a CRD in place, you’d have a NewDB resource that could specify things like:

• Number of replicas