Operators

An Operator is an idea. Here software manages applications and services. It automates deployment, upgrades, scaling, backup, and more.

Why the word operator?

In general, operators are people who work in IT operations. They manage the full lifecycle of applications and services.

In Kubernetes, these are just software programs that act as physical operators.

Parts of Operators

1. Controller - This is the main admin software. It runs inside a Kubernetes cluster. It watches the cluster state. It makes changes to keep the desired state.
2. Custom Resource Definitions (CRDs) - These extend the Kubernetes API server. They let users define their own resource types. They're the API objects added to the cluster.
3. Custom Resources - These are instances of the CRDs. They hold the desired state of the app or service the Operator manages.
4. Reconciliation Loop - This is the controller's main job. It watches the custom resources the user creates. It compares them to the real cluster state. If they differ, the controller takes the steps to fix the resources.

useful link

Idea of operators - CoreOS