What is Kubernetes Pod Scheduling Gate?

Question

Accepted Answer

**Scheduling Gates** — prevent Pod scheduling until gates are opened.

```yaml
apiVersion: v1
kind: Pod
metadata:
  name: gated-pod
spec:
  schedulingGates:
  - name: "scheduling.mycompany.com/approved"
  - name: "scheduling.mycompany.com/budget-check"
  containers:
  - name: app
    image: myapp:latest
    resources:
      requests:
        cpu: "2"
        memory: "4Gi"
```

```bash
# Check scheduling gates
kubectl get pod gated-pod -o jsonpath='{.spec.schedulingGates}' | jq

# Open a gate
kubectl patch pod gated-pod --type=json -p '[{"op":"remove","path":"/spec/schedulingGates/0"}]'

# Check gate status
kubectl get pod gated-pod -o jsonpath='{.spec.schedulingGates}' | jq

# Watch for scheduling
kubectl get pods -w
kubectl get events --field-selector reason=Scheduled

# Verify Pod is scheduled after gates removed
kubectl get pod gated-pod -o jsonpath='{.spec.nodeName}'
```

```go
// Controller to remove gates
func (r *ApprovalReconciler) Reconcile(ctx context.Context, req ctrl.Request) {
    var pod corev1.Pod
    if err := r.Get(ctx, req.NamespacedName, &pod); err != nil {
        return ctrl.Result{}, err
    }

// Check approval
    if !isApproved(pod) {
        return ctrl.Result{RequeueAfter: 10 * time.Second}, nil
    }

// Remove gate
    pod.Spec.SchedulingGates = removeGate(pod.Spec.SchedulingGates, "scheduling.mycompany.com/approved")
    return ctrl.Result{}, r.Update(ctx, &pod)
}
```

**Use cases:**
- Custom scheduling logic.
- Approval workflows.
- Budget checks.
- Resource reservation.

DevOps: What is Kubernetes Pod Scheduling Gate?