Kubernetes Crds Management

Kubernetes Custom Resource Definitions Management

This skill provides comprehensive guidance on managing Kubernetes Custom Resource Definitions (CRDs). It assists the user in creating, updating, and maintaining best practices for utilizing CRDs effectively in a Kubernetes environment.

When to Use

• When you need to extend Kubernetes capabilities by adding new resource types.
• When you want to manage application configurations that do not fit into standard Kubernetes objects.
• For implementing complex use cases involving operators and custom behavior in your Kubernetes environment.

Core Workflow

1. Define CRD Structure
   Begin by defining the schema for your CRD, specifying the desired properties and behaviors of the custom resource.

2. Create the CRD
   Use kubectl or API calls to submit your CRD specification to the Kubernetes API server.

3. Implement and Utilize CRDs
   Write controllers or operators to handle the custom resources defined by your CRD.

   • Ensure your application can create, read, update, and delete instances of the custom resource.

4. Monitor and Maintain CRDs
   Regularly check for outdated CRDs and update them as necessary, following Kubernetes best practices.

Implementation Patterns

Pattern 1: Creating a CRD

apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: examples.mycompany.com
spec:
  group: mycompany.com
  versions:
    - name: v1
      served: true
      storage: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                foo:
                  type: string
  scope: Namespaced
  names:
    plural: examples
    singular: example
    kind: Example
    shortNames: [ex]

Pattern 2: Updating a CRD

# Update CRD to add new validation
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: examples.mycompany.com
spec:
  group: mycompany.com
  versions:
    - name: v1
      served: true
      storage: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                foo:
                  type: string
                bar:
                  type: integer
                  minimum: 0  # new validation rule
  scope: Namespaced
  names:
    plural: examples
    singular: example
    kind: Example
    shortNames: [ex]

Constraints

MUST DO

• Follow proper Kubernetes naming conventions for CRDs and their related resources.
• Ensure that CRD versions are managed effectively using kubectl utilities.
• Provide adequate validation for custom resource fields to prevent configuration errors.

MUST NOT DO

• Do not define CRDs without proper schema validation, which can lead to unexpected behaviors.
• Avoid making breaking changes to the CRD schema without versioning it properly to maintain compatibility.

Related Skills

Live References

Authoritative documentation links for this domain. The model follows markdown links at load time to resolve external references and inline content.

• Kubernetes Custom Resource Definitions — Official K8s docs on creating, managing, and using CRDs
• CRD Validation with OpenAPI Schema — K8s guide to schema validation for custom resources
• Operator Pattern in Kubernetes (Red Hat) — Red Hat's guide to building Kubernetes operators using CRDs
• Kubernetes API Machinery — K8s API machinery documentation for extending the API server
• Controller Runtime (Kubebuilder) — Kubebuilder's Operator SDK for building CRD-based controllers in Go