kubernetes-operator-dev

# Kubernetes Operator Dev ## Overview This skill provides expert guidance on designing, building, and deploying Kubernetes Operators. It focuses on the **Operator Pattern** to automate complex application lifecycle management. **Primary Frameworks:** - **Python**: [Kopf (Kubernetes Operator Pythonic Framework)](https://kopf.readthedocs.io/) - Best for data science, AI/ML workloads, and Python teams. - **Go**: [Kubebuilder](https://book.kubebuilder.io/) / [Operator SDK](https://sdk.operatorframework.io/) - Best for high-performance, core infrastructure operators. ## Core Capabilities 1. **CRD Design**: Modeling custom resources (APIs) with OpenAPI v3 schemas. 2. **Reconciliation**: Implementing idempotent loops to bring current state to desired state. 3. **Event Handling**: Reacting to Create/Update/Delete events on resources. 4. **Finalizers**: Ensuring clean resource cleanup and deletion logic. 5. **Testing**: Unit testing handlers and end-to-end testing with Kind/Minikube. ## Python Operator Workflow (Kopf) ### 1. Project Structure ```text my-operator/ ├── deploy/ │ ├── crd.yaml # CustomResourceDefinition │ ├── rbac.yaml # ServiceAccount, Role, RoleBinding │ └── operator.yaml # Deployment ├── src/ │ └── handlers.py # Python logic ├── Dockerfile └── requirements.txt # kopf, kubernetes ``` ### 2. Basic Handler Pattern ```python import kopf import kubernetes.client as k8s @kopf.on.create('my-group', 'v1', 'mycustomresources') def create_fn(spec, name, namespace, logger, **kwargs): """ Called when a new MyCustomResource is created. """ size = spec.get('size', 1) logger.info(f"Creating resource {name} with size {size}") # Logic to create child resources (e.g., Pods, Services) api = k8s.CoreV1Api() # ... implementation ... return {'message': 'created', 'time': kopf.now()} ``` ### 3. Idempotency & Error Handling - **Idempotency**: Handlers must be safe to run multiple times. Check if a child resource exists before creating it. - **Retries**: Raise `kopf.TemporaryError` for transient failures (e.g., network issues) to trigger a retry with backoff. - **Permanent Errors**: Raise `kopf.PermanentError` to stop retries for invalid configuration. ## Best Practices - **Status Subresource**: Always use the `status` subresource to report observation (e.g., `Ready`, `Phase`, `Conditions`). Do not update `spec`. - **Owner References**: Set `ownerReferences` on child resources so they are garbage collected when the parent CR is deleted. - **RBAC**: Grant only the necessary permissions (Least Privilege). - **Structured Logging**: Use the provided `logger` to ensure logs are JSON-formatted and traceable. - **Namespace Scoping**: Decide if your operator is namespaced or cluster-wide. ## Deployment Checklist 1. [ ] **CRD Registered**: Apply `crd.yaml` first. 2. [ ] **RBAC Configured**: Ensure the ServiceAccount has permissions to watch/list/update the CRs and manage child resources. 3. [ ] **Image Built**: Build multi-arch image (amd64/arm64) for production. 4. [ ] **Liveness/Readiness**: Configure probes in the Deployment. 5. [ ] **Monitoring**: Expose metrics (Prometheus) if needed. ## Common Commands - **Run locally (dev)**: `kopf run src/handlers.py --verbose` - **Build image**: `docker build -t my-operator:v1 .` - **Apply manifest**: `kubectl apply -f deploy/` - **View logs**: `kubectl logs -l app=my-operator -f`