Kubectl accepted yamls: will it deploy?

General Discussions
1

Hi,

I’ve been investigating the types of YAML documents kubectl -f accepts for deployment.

I’ve found out that the following are accepted:

A single element in one file

apiVersion: v1
kind: ConfigMap
data:
  key: value
metadata:
  name: config-single-element

It deploys. Now we try one file, with two YAML documents:

apiVersion: v1
kind: ConfigMap
data:
  key: value
metadata:
  name: config-two-elements-1
---
apiVersion: v1
kind: ConfigMap
data:
  key: value
metadata:
  name: config-two-elements-2

It deploys. Now one file with a List object:

apiVersion: v1
kind: List
items:
 - apiVersion: v1
   kind: ConfigMap
   data:
     key: value
   metadata:
     name: config-list-1
 - apiVersion: v1
   kind: ConfigMap
   data:
     key: value
   metadata:
     name: config-list-2

It deploys. So I continue playing, combining a two document YAML file. One part with an object, and the other with a List:

apiVersion: v1
kind: List
items:
 - apiVersion: v1
   kind: ConfigMap
   data:
     key: value
   metadata:
     name: config-list-and-single-1
 - apiVersion: v1
   kind: ConfigMap
   data:
     key: value
   metadata:
     name: config-list-and-single-2
---
apiVersion: v1
kind: ConfigMap
data:
  key: value
metadata:
  name: config-list-and-single-3

It deploys. Up till here all of these examples are accepted by kubectl apply -f, so I started getting creative: What if we put a List object in a List. Will it deploy?

apiVersion: v1
kind: List
items:
 - apiVersion: v1
   kind: List
   items:
    - apiVersion: v1
      kind: ConfigMap
      data:
        key: value
      metadata:
        name: config-list-within-list-1
    - apiVersion: v1
      kind: ConfigMap
      data:
        key: value
      metadata:
        name: config-list-within-list-2

It doesn’t deploy :frowning: with the following error:

error: no Items field in &unstructured.Unstructured{Object:map[string]interface {}{“apiVersion”:“v1”, “items”:interface {}{map[string]interface {}{“apiVersion”:“v1”, “data”:map[string]interface {}{“key”:“value”}, “kind”:“ConfigMap”, “metadata”:map[string]interface {}{“name”:“config-list-within-list-1”}}, map[string]interface {}{“apiVersion”:“v1”, “data”:map[string]interface {}{“key”:“value”}, “kind”:“ConfigMap”, “metadata”:map[string]interface {}{“name”:“config-list-within-list-2”}}}, “kind”:“List”}}

The error is a bit strange: I can’t find the missing “items” field. Should this be accepted by kubectl? Or is it explicitly prohibited?

2

I think it is explicitly prohibited. I think the kind list is type v1 APIResourceList and only accept APIResource as items.

But I’m not really sure. I encourage you to go to the code and have a look! It surely be fun.

And if it’s not accepted in purpose, you can send a patch to document it more clearly if you think that is relevant for others too :slight_smile: