func()

in pkg/crossnodepreemption/cross_node_preemption.go [71:123]

• 35 lines of code
• 9 McCabe index (conditional complexity)

func (pl *CrossNodePreemption) preempt(ctx context.Context, state *framework.CycleState, pod *v1.Pod, m framework.NodeToStatusMap) (string, *framework.Status) {
	cs := pl.fh.ClientSet()
	nodeLister := pl.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 := pl.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 !dp.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 := FindCandidates(ctx, state, pod, m, pl.fh, nodeLister)
	if !status.IsSuccess() {
		return "", status
	}

	// Return a FitError only when there are no candidates that fit the pod.
	if len(candidates) == 0 {
		fitError := &framework.FitError{
			Pod: pod,
		}
		return "", framework.NewStatus(framework.Unschedulable, fitError.Error())
	}

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

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

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

	return bestCandidate.Name(), nil
}