API: Adds default status condition to InferencePool

[danehans]

Adds default status condition to the InferencePool API.

Fixes #825

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[danehans]

/cc @robscott

Tested in my dev cluster:

$ kubectl get inferencepool/test -o yaml
...
status:
  parent:
  - conditions:
    - lastTransitionTime: "1970-01-01T00:00:00Z"
      message: Waiting for controller
      reason: Pending
      status: Unknown
      type: Accepted
    parentRef: {}

[kfswain]

/approve

Will leave final stamp to @robscott

[danehans]

Since the default parent status contains an empty parentRef, the entry persists even after a Gateway adds a parent status entry. For example:

$ kubectl get inferencepool/vllm-llama3-8b-instruct -o yaml
...
status:
  parent:
  - conditions:
    - lastTransitionTime: "1970-01-01T00:00:00Z"
      message: Waiting for controller
      reason: Pending
      status: Unknown
      type: Accepted
    parentRef: {}
  - conditions:
    - lastTransitionTime: "2025-05-15T00:04:05Z"
      message: InferencePool is accepted by controller kgateway.dev/kgateway
      reason: Accepted
      status: "True"
      type: Accepted
    - lastTransitionTime: "2025-05-15T00:04:05Z"
      message: All InferencePool references are resolved
      reason: ResolvedRefs
      status: "True"
      type: ResolvedRefs
    parentRef:
      kind: Gateway
      name: inference-gateway

We should update the InferencePool API to define the expected behavior of the default PoolStatus. For example:

1. A controller that adds itself as a status parent must remove the default parent status if it exists.
2. A controller that removes itself as a status parent and no other parents are listed in the InferencePool status, must add the default parent status.

Thoughts @robscott

[robscott]

Thanks for doing this @danehans!

We should update the InferencePool API to define the expected behavior of the default PoolStatus. For example:

1. A controller that adds itself as a status parent must remove the default parent status if it exists.
2. A controller that removes itself as a status parent and no other parents are listed in the InferencePool status, must add the default parent status.

Completely agree. I think 1) is a MUST, while 2) is a SHOULD. If you can add this to API Spec, I'll LGTM.

[robscott]

What if instead of an empty parentRef, we filled it with something like {kind: Status, name: default}, or some kind of similar distinction so it's easier for controllers to know that they can safely remove this.

[danehans]

cc @SinaChavoshi related to conformance tests

[nirrozenbaum]

/test pull-gateway-api-inference-extension-test-e2e-main

[kfswain]

Bump on this PR, the conversation makes sense to me. I think implementation of that will put this PR in a good state.

[danehans]

@robscott PTAL when you have a moment.

[robscott]

Thanks @danehans!

/lgtm

[robscott]

@zetxqx I think we'll likely need some conformance test coverage here to ensure that controllers drop this condition from status. It's possible that our existing conformance tests will already cover this though.

[zetxqx]

ack!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: danehans, kfswain, robscott

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