RayJob Volcano Integration

[win5923]

Why are these changes needed?

• RayJob Volcano support: Adds Volcano scheduler support for RayJob CRD.
• Gang scheduling: Ensures Ray pods are scheduled together as a unit, preventing partial scheduling issues.
• Unified interface: Consolidates all batch schedulers to use AddMetadataToChildResource() for consistency.

E2E

1. Deploy the KubeRay operator with the batch-scheduler volcano:

./ray-operator/bin/manager -leader-election-namespace default -use-kubernetes-proxy -batch-scheduler=volcano

2. Create a RayJob with a head node (1 CPU + 2Gi of RAM), two workers (1 CPU + 1Gi of RAM each) and one submitter pod (0.5 CPU + ~0.2Gi of RAM), for a total of 3.5 CPU and 4.2Gi of RAM

kubectl apply -f ray-operator/config/samples/ray-job.volcano-scheduler-queue.yaml

3. Add an additional RayJob with the same configuration but with a different name

sed 's/rayjob-sample-0/rayjob-sample-1/' ray-operator/config/samples/ray-job.volcano-scheduler-queue.yaml | kubectl apply -f-

4. All the pods stuck on pending for new RayJob

$ k get podgroup ray-rayjob-sample-1-pg  -o yaml
apiVersion: scheduling.volcano.sh/v1beta1
kind: PodGroup
metadata:
  creationTimestamp: "2025-09-11T16:32:51Z"
  generation: 2
  name: ray-rayjob-sample-1-pg
  namespace: default
  ownerReferences:
  - apiVersion: ray.io/v1
    blockOwnerDeletion: true
    controller: true
    kind: RayJob
    name: rayjob-sample-1
    uid: 3e5d1ad3-0d35-401b-8d50-3d9f850add38
  resourceVersion: "12126"
  uid: 927dc6e4-0b8b-4d7a-8838-19496cc171b7
spec:
  minMember: 3
  minResources:
    cpu: "3"
    memory: 4Gi
  queue: kuberay-test-queue
status:
  conditions:
  - lastTransitionTime: "2025-09-11T16:32:52Z"
    message: '3/3 tasks in gang unschedulable: pod group is not ready, 3 Pending,
      3 minAvailable; Pending: 3 Unschedulable'
    reason: NotEnoughResources
    status: "True"
    transitionID: 7ae91b28-f1ed-4599-8147-f3ca7520f00d
    type: Unschedulable
  phase: Pending

$ k get queue kuberay-test-queue -o yaml
apiVersion: scheduling.volcano.sh/v1beta1
kind: Queue
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"scheduling.volcano.sh/v1beta1","kind":"Queue","metadata":{"annotations":{},"name":"kuberay-test-queue"},"spec":{"capability":{"cpu":4,"memory":"6Gi"},"weight":1}}
  creationTimestamp: "2025-09-11T16:29:27Z"
  generation: 2
  name: kuberay-test-queue
  resourceVersion: "11903"
  uid: 43d0c1d3-fb1b-447a-a4db-3b52007d37c6
spec:
  capability:
    cpu: 4
    memory: 6Gi
  parent: root
  reclaimable: true
  weight: 1
status:
  allocated:
    cpu: "3"
    memory: 4Gi
    pods: "3"
  reservation: {}
  state: Open

Related issue number

Closes #1580

Checks

• I've made sure the tests are passing.
• Testing Strategy
  • Unit tests
  • Manual tests
  • This PR is not tested :(