2025 Updates Operator Framework

This article explains the Operator Framework: what an operator is, how it relates to CustomResourceDefinitions (CRDs) and controllers, and how operators are packaged and deployed. It also includes a minimal example (CRD, controller snippet, and installation command) and guidance for deploying operators via OperatorHub and the Operator Lifecycle Manager (OLM).

What is an operator?

An operator packages Kubernetes application knowledge — the human operational procedures required to install, upgrade, back up, and recover an application — into code that runs inside the cluster. Operators combine:

A CustomResourceDefinition (CRD) that declares a new Kubernetes API kind.
One or more controllers that watch and reconcile instances of that CRD, implementing domain-specific logic.

Operators effectively bundle CRDs and controllers into a single, deployable unit so you can deliver application-specific operations in a repeatable, automated way. Common operator responsibilities:

Provisioning and configuring application instances (create/update).
Automated backups and restores.
Upgrades and schema migrations.
Failure detection and remediation.
Exposing operational metrics and status.

Popular operators (available on OperatorHub) include etcd, MySQL, Prometheus, Grafana, Argo CD, and Istio.

Key concepts and mapping

Component	Role	Example
CustomResourceDefinition (CRD)	Defines a new Kubernetes API type and schema	`FlightTicket` CRD YAML (see example below)
Custom Resource (CR)	An instance of the CRD that represents an application request or configuration	`FlightTicket` object created by users
Controller	Reconciles CRs and implements operational logic	Go controller reconciling `FlightTicket` resources
Operator	A packaged delivery that includes CRDs, controllers, and optional subcomponents (backup/restore)	etcd operator that creates `etcdCluster` CRD and runs controllers

Minimal operator example

Below is a compact example illustrating the three parts you typically see in an operator package: the CRD YAML, a simplified Go controller snippet, and the command used to deploy the operator manifest. CRD example:

apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: flighttickets.flights.com
spec:
  scope: Namespaced
  group: flights.com
  names:
    kind: FlightTicket
    singular: flightticket
    plural: flighttickets
    shortNames:
      - ft
  versions:
    - name: v1
      served: true
      storage: true

Controller (Go) — simplified snippets:

package flightticket

// controllerKind is used to identify the controller's primary resource.
var controllerKind = apps.SchemeGroupVersion.WithKind("FlightTicket")

// <Code hidden>

// Run begins watching and syncing.
func (dc *FlightTicketController) Run(workers int, stopCh <-chan struct{}) {
    // <Code hidden>
}

// Call BookFlightAPIReplicaSet
func (dc *FlightTicketController) callBookFlightAPI(obj interface{}) {
    // <A lot of code hidden>
}

Deploy the operator manifest (example):

$ kubectl create -f flight-operator.yaml

Example: etcd operator and higher-level behaviors

The etcd operator is a good real-world example: when installed it creates the etcdCluster CRD, allows CRs to request etcd clusters, and runs controllers to reconcile those CRs. Operators like this often include additional subcomponents or controllers for scheduled backups, restores, and other operational flows (commonly called backup and restore operators).

A diagram of an Operator Framework showing Custom Resource Definitions (EtcdCluster, EtcdBackup, EtcdRestore) on the left and corresponding custom controllers/operators (ETCD Controller, Backup Operator, Restore Operator) on the right. The layout illustrates how CRDs map to their controllers within the operator framework.

Deploying operators from OperatorHub

OperatorHub hosts many prebuilt operators. Typical high-level steps to deploy an operator from OperatorHub:

Step	What it does	Example / command
1. Install OLM	Provides lifecycle management for operators	`curl -sL https://github.com/operator-framework/operator-lifecycle-manager/releases/download/v0.32.0/install.sh \| bash -s v0.32.0`
2. Install operator	Install via OLM or apply operator manifest directly	`kubectl create -f https://operatorhub.io/install/etcd.yaml`
3. Create CRs	Create instances of the operator-provided CRDs to request app instances	`kubectl apply -f my-etcd-cluster.yaml`

Example commands (install a specific OLM release and the etcd operator):

# Install Operator Lifecycle Manager (example version)
$ curl -sL https://github.com/operator-framework/operator-lifecycle-manager/releases/download/v0.32.0/install.sh | bash -s v0.32.0

# Install the etcd operator from OperatorHub manifest
$ kubectl create -f https://operatorhub.io/install/etcd.yaml

# Verify ClusterServiceVersions in the target namespace (example namespace)
$ kubectl get csv -n my-etcd

Operator responsibilities and implementation details vary by project. Some operators only manage lifecycle (install/upgrade), while others include complex operational logic like automated backups, restores, and recovery workflows. When evaluating an operator, review its CRDs, ClusterServiceVersion (CSV), and documentation for exact capabilities.

When operators matter for exams and practical use

For most Kubernetes certification objectives and fundamentals, focus on:

Understanding CRDs and how they extend the Kubernetes API.
How controllers watch resources and reconcile desired state.
How to deploy CRDs and controllers (manually or via an operator).

Operators extend those fundamentals into a packaged delivery mechanism that automates operational tasks. Studying operators is valuable when you need to manage complex applications in Kubernetes, but full operator design and implementation is a broader topic that may require additional focused learning.

Links and references

Operator Framework / OLM: https://operatorframework.io/
OperatorHub: https://operatorhub.io/
etcd: https://etcd.io/
Kubernetes API and CRDs: https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/
Prometheus: https://prometheus.io/
Grafana: https://grafana.com/
Argo CD docs: https://argo-cd.readthedocs.io/en/stable/
Istio: https://istio.io/

Thank you — that concludes this lesson on the Operator Framework.

Introduction

Core Concepts

Scheduling

Logging & Monitoring

Application Lifecycle Management

Cluster Maintenance

Security

Storage

Networking

Design and Install a Kubernetes Cluster

Install "Kubernetes the kubeadm way"

Troubleshooting

Helm Basics (2025 Updates)

Kustomize Basics (2025 Updates)

Other Topics

Mock Exams

2025 Updates Operator Framework

What is an operator?

Key concepts and mapping

Minimal operator example

Example: etcd operator and higher-level behaviors

Deploying operators from OperatorHub

When operators matter for exams and practical use

Links and references

Watch Video

​What is an operator?

​Key concepts and mapping

​Minimal operator example

​Example: etcd operator and higher-level behaviors

​Deploying operators from OperatorHub

​When operators matter for exams and practical use

​Links and references

Watch Video

What is an operator?

Key concepts and mapping

Minimal operator example

Example: etcd operator and higher-level behaviors

Deploying operators from OperatorHub

When operators matter for exams and practical use

Links and references