Missing default value in nested field of kubernetes custom resource

Question

I have a Custom Resource Definition which has nested fields with default values (some boilerplate omitted for brevity):

apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
spec:
  scope: Namespaced
  group: thismatters.stackoverflow
  names:
    kind: BadDefault
  versions:
  - name: v1alpha
    schema:
      openAPIV3Schema:
        type: object
        properties:
          spec:
            type: object
            properties:
              regularThing:
                type: integer
                default: 6
              shouldDefault:
                type: object
                properties:
                  nestedThing:
                    type: integer
                    default: 12

Whenever I create a resource of this kind without specifying the shouldDefault object:

apiVersion: thismatters.stackoverflow/v1alpha
kind: BadDefault
metadata:
  name: blank-demo
spec: 
  regularThing: 7

The default value for .shouldDefault.nestedThing doesn't appear when the resource is described:

apiVersion: thismatters.stackoverflow/v1alpha
kind: BadDefault
metadata:
  name: blank-demo
spec: 
  regularThing: 7

If I update the resource with this manifest:

apiVersion: thismatters.stackoverflow/v1alpha
kind: BadDefault
metadata:
  name: blank-demo
spec: 
  regularThing: 7
  shouldDefault: {}

Then the nested field default value is populated when described:

apiVersion: thismatters.stackoverflow/v1alpha
kind: BadDefault
metadata:
  name: blank-demo
spec: 
  regularThing: 7
  shouldDefault:
    nestedThing: 12

Is there anything I can do in the CRD to remove the need for the shouldDefault: {} line in the resource manifest and have the default values populate in the nested fields?

My cluster is on Kubernetes version 1.19.

You are using deprecated version of Kubernetes. Could you update it to [supported one](https://endoflife.date/kubernetes)? — Mikołaj Głodziak, Dec 30 '21 at 08:34
1.19 is still supported in EKS (even 1.18 is still supported). Is there a known issue in 1.19 that prevents default values of nested fields from being autopopulated? — Thismatters, Dec 30 '21 at 11:54

score 1 · Accepted Answer · answered Dec 31 '21 at 02:54

Adding a default property to the shouldDefault object fixes this:

apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
spec:
  scope: Namespaced
  group: thismatters.stackoverflow
  names:
    kind: BadDefault
  versions:
  - name: v1alpha
    schema:
      openAPIV3Schema:
        type: object
        properties:
          spec:
            type: object
            properties:
              regularThing:
                type: integer
                default: 6
              shouldDefault:
                type: object
                default: {}   #  <-- this was added
                properties:
                  nestedThing:
                    type: integer
                    default: 12

Missing default value in nested field of kubernetes custom resource

1 Answers1