K8s Operator with OLM

A Kubernetes operator built with Operator SDK and deployed via Operator Lifecycle Manager (OLM).

Overview

This operator manages two deployments (web-application and data-db) through a Custom Resource Definition (CRD) called K8soperator.

Prerequisites

• Kubernetes cluster with OLM installed
• Docker registry access
• Tools: operator-sdk, opm, kubectl, docker

Architecture

Custom Resource (CR) → CRD → Operator Controller → Managed Resources

CRD Development Process

1. Initialize Operator Project

operator-sdk init --domain=mydomain.com --repo=github.com/user/k8soperator

2. Create API and Controller

operator-sdk create api --group=apps --version=v1alpha1 --kind=K8soperator --resource --controller

3. Define CRD Schema

Edit api/v1alpha1/k8soperator_types.go:

type K8soperatorSpec struct {
    Replicas int32 `json:"replicas,omitempty"`
}

4. Generate CRD Manifests

make generate manifests

OLM Deployment Process

1. Build and Push Operator Image

make build docker-build docker-push IMG=<registry>/k8soperator:v0.1.2

2. Generate OLM Bundle

make bundle VERSION=0.1.2
make bundle-build bundle-push BUNDLE_IMG=<registry>/k8soperator-bundle:v0.1.2

3. Create Catalog Index

make catalog-render catalog-build catalog-push INDEX_IMG=<registry>/k8soperator-index:v0.1.2

4. Deploy via OLM

# Create CatalogSource
kubectl apply -f catalogsource.yaml

# Create OperatorGroup
kubectl apply -f - <<EOF
apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: k8soperator-operatorgroup
  namespace: default
spec:
  targetNamespaces:
  - default
EOF

# Create Subscription
kubectl apply -f - <<EOF
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: k8soperator-subscription
  namespace: default
spec:
  channel: stable
  name: k8soperator
  source: k8soperator-catalog
  sourceNamespace: olm
EOF

How CRD Gets Installed

1. Bundle Creation: CRD manifests are packaged in the operator bundle
2. CSV Definition: ClusterServiceVersion references the CRD in spec.customresourcedefinitions.owned
3. OLM Installation: When subscription is created, OLM:
   • Reads the CSV from catalog
   • Installs CRDs defined in CSV
   • Deploys operator controller
   • Manages lifecycle

Usage

Create a Custom Resource:

apiVersion: apps.mydomain.com/v1alpha1
kind: K8soperator
metadata:
  name: k8soperator-sample
  namespace: default
spec:
  replicas: 1

Quick Deploy

# Clean install
./clean-reinstall.sh

# Manual deploy
./deploy-olm.sh

Verification

# Check operator status
kubectl get csv,subscription,operatorgroup -n default

# Check CRD
kubectl get crd k8soperators.apps.mydomain.com

# Check managed resources
kubectl get k8soperators,deployments,services -n default

Key Files

• api/v1alpha1/k8soperator_types.go - CRD schema definition
• config/crd/bases/ - Generated CRD manifests
• config/manifests/bases/k8soperator.clusterserviceversion.yaml - CSV template
• bundle/ - OLM bundle artifacts
• catalog/ - Catalog index configuration

Cleanup

kubectl delete subscription k8soperator-subscription -n default
kubectl delete catalogsource k8soperator-catalog -n olm

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Author

Vasudev Chavan