Kubernetes Operators: The Reconciliation Loop

Tue, 20 Oct 2026 00:00:00 +0000

This is part 3 of a four-part series on building a Kubernetes operator: CRDs , Custom Resources , Operators (this post) and Kubebuilder .

Pattern and Not Kubernetes Built-In

An “operator” is not a Kubernetes resource type or an API, I would consider it an architectural pattern: It comprises of a Custom Resource Definition (CRD) that describes the desired state (covered in part one), and a controller that watches Custom Resource (CR) instances (covered in part two) and drives them towards this desired state. Something can be considered an operator rather than “just a controller” when it encodes real operational knowledge, which would otherwise live in a runbook, and runs continuously instead of being triggered by a human. You can think of a Kubernetes operator as the software representation of a human operator.

Controllers on Felix Seifert

Kubernetes Operators: The Reconciliation Loop

Pattern and Not Kubernetes Built-In