func()

in pkg/capacityscheduling/capacity_scheduling.go [304:348]

• 29 lines of code
• 8 McCabe index (conditional complexity)

func (c *CapacityScheduling) preempt(ctx context.Context, state *framework.CycleState, pod *v1.Pod, m framework.NodeToStatusMap) (string, *framework.Status) {
	client := c.fh.ClientSet()
	nodeLister := c.fh.SnapshotSharedLister().NodeInfos()

	// Fetch the latest version of <pod>.
	// It's safe to directly fetch pod here. Because the informer cache has already been
	// initialized when creating the Scheduler obj, i.e., factory.go#MakeDefaultErrorFunc().
	// However, tests may need to manually initialize the shared pod informer.
	pod, err := c.podLister.Pods(pod.Namespace).Get(pod.Name)
	if err != nil {
		klog.Errorf("Error getting the updated preemptor pod object: %v", err)
		return "", framework.AsStatus(err)
	}

	// 1) Ensure the preemptor is eligible to preempt other pods.
	if !defaultpreemption.PodEligibleToPreemptOthers(pod, nodeLister, m[pod.Status.NominatedNodeName]) {
		klog.V(5).Infof("Pod %v/%v is not eligible for more preemption.", pod.Namespace, pod.Name)
		return "", nil
	}

	// 2) Find all preemption candidates.
	candidates, status := c.FindCandidates(ctx, client, state, pod, m)
	if !status.IsSuccess() {
		return "", status
	}

	// 3) Interact with registered Extenders to filter out some candidates if needed.
	candidates, status = defaultpreemption.CallExtenders(c.fh.Extenders(), pod, nodeLister, candidates)
	if !status.IsSuccess() {
		return "", status
	}

	// 4) Find the best candidate.
	bestCandidate := defaultpreemption.SelectCandidate(candidates)
	if bestCandidate == nil || len(bestCandidate.Name()) == 0 {
		return "", nil
	}

	// 5) Perform preparation work before nominating the selected candidate.
	if status := defaultpreemption.PrepareCandidate(bestCandidate, c.fh, client, pod, c.Name()); !status.IsSuccess() {
		return "", status
	}

	return bestCandidate.Name(), nil
}