Scenario

You manage a CustomResourceDefinition (CRD) for "Widgets". Currently, the API allows users to create widgets with missing or invalid configuration, which causes the controller to crash. You need to enforce strict validation at the API level to reject bad data before it enters the cluster.

Task

Modify the existing widgets.mycompany.io CRD to enforce a schema. Require the field spec.size to be present. Restrict spec.size to be an integer with a minimum value of 1. Attempt to create a custom resource named bad-widget (provided in the file bad-widget.yaml) that is missing the size field. Verify that the creation fails and the resource is not created.

Example

Initial State (Loose Schema):

# The CRD accepts any random fields (or lack thereof)
$ kubectl explain widget.spec
<empty>

Success State (Strict Schema):

# The API rejects invalid data
$ kubectl apply -f bad-widget.yaml
The Widget "bad-widget" is invalid: spec.size: Required value

# The resource should NOT appear in the list
$ kubectl get widget bad-widget
Error from server (NotFound): widgets.mycompany.io "bad-widget" not found

Step 1: Inspect the Invalid Resource
View the file provided in your environment. It lacks the size field.

cat bad-widget.yaml

Step 2: Update the CRD Schema
Edit the CRD configuration to add the validation rules.

kubectl edit crd widgets.mycompany.io

Locate the openAPIV3Schema section and update it to look like this:

      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              required: ["size"]    # Rule 1: size is mandatory
              properties:
                size:
                  type: integer     # Rule 2: must be integer
                  minimum: 1        # Rule 3: must be >= 1

Save and exit the editor. You should see "customresourcedefinition.apiextensions.k8s.io/widgets.mycompany.io edited".

Step 3: Verify Validation
Try to apply the invalid resource. This must fail.

kubectl apply -f bad-widget.yaml
# Expected Output:
# The Widget "bad-widget" is invalid: spec.size: Required value

Check that the resource was blocked

kubectl get widget bad-widget
# Expected Output: Error from server (NotFound)