🚀 Operator SDK

What is an Operator

A controller is a loop that watches Kubernetes objects and reconciles their desired state (the spec) with the actual state (the cluster).

An Operator is a controller with operational knowledge baked in: it knows how to install, configure, scale, back up and upgrade an application — the jobs a human admin used to do by hand.

1desired state (CR)  ──►  reconcile loop  ──►  actual state (cluster)

Classic examples: etcd-operator, prometheus-operator.

What Operator SDK provides

Writing that reconcile loop by hand means a lot of boilerplate: CRDs, client code, RBAC, controller scaffolding, watch wiring. Operator SDK (from the Operator Framework) automates it:

• operator-sdk init — scaffold the Go module, Makefile, Dockerfile and config/ (CRDs, RBAC, manager, samples).
• operator-sdk create api — generate the CRD type + the controller that watches it.
• RBAC markers and a ready-made reconcile skeleton, so you only write the business logic.

The three kinds

Operators have 3 kinds: Go, Ansible, Helm.

watches.yaml maps a given CR to the Ansible role/playbook that must run when an object of that kind appears.

Init an Ansible operator

1# Init an Ansible project
2operator-sdk init --plugins=ansible --domain example.org --owner "Your name"

The command creates the following structure:

 1netbox-operator
 2├── Dockerfile
 3├── Makefile
 4├── PROJECT
 5├── config
 6│   ├── crd
 7│   ├── default
 8│   ├── manager
 9│   ├── manifests
10│   ├── prometheus
11│   ├── rbac
12│   ├── samples
13│   ├── scorecard
14│   └── testing
15├── molecule
16│   ├── default
17│   └── kind
18├── playbooks
19│   └── install.yml
20├── requirements.yml
21├── roles
22│   └── deployment
23└── watches.yaml

Create a CRD / API

1# Create the first API and generate the role
2operator-sdk create api --group app --version v1alpha1 --kind Deployment --generate-role