func()

in pkg/preemptiontoleration/preemption_toleration.go [184:286]

• 84 lines of code
• 19 McCabe index (conditional complexity)

func (pl *PreemptionToleration) SelectVictimsOnNode(
	ctx context.Context,
	state *framework.CycleState,
	preemptor *v1.Pod,
	nodeInfo *framework.NodeInfo,
	pdbs []*policy.PodDisruptionBudget) ([]*v1.Pod, int, *framework.Status) {
	var potentialVictims []*framework.PodInfo
	logger := klog.FromContext(ctx)
	removePod := func(rpi *framework.PodInfo) error {
		if err := nodeInfo.RemovePod(logger, rpi.Pod); err != nil {
			return err
		}
		status := pl.fh.RunPreFilterExtensionRemovePod(ctx, state, preemptor, rpi, nodeInfo)
		if !status.IsSuccess() {
			return status.AsError()
		}
		return nil
	}
	addPod := func(api *framework.PodInfo) error {
		nodeInfo.AddPodInfo(api)
		status := pl.fh.RunPreFilterExtensionAddPod(ctx, state, preemptor, api, nodeInfo)
		if !status.IsSuccess() {
			return status.AsError()
		}
		return nil
	}

	// As the first step, remove all lower priority pods that can't tolerate preemption by the preemptor
	// from the node and check if the given pod can be scheduled.
	podPriority := corev1helpers.PodPriority(preemptor)
	for _, pi := range nodeInfo.Pods {
		if corev1helpers.PodPriority(pi.Pod) >= podPriority {
			continue
		}

		// For a pod with lower priority, check if it can be exempted from the preemption.
		exempted, err := ExemptedFromPreemption(pi.Pod, preemptor, pl.priorityClassLister, pl.curTime)
		if err != nil {
			klog.ErrorS(err, "Encountered error while selecting victims on node", "Node", nodeInfo.Node().Name)
			return nil, 0, framework.AsStatus(err)
		}

		if !exempted {
			potentialVictims = append(potentialVictims, pi)
			if err := removePod(pi); err != nil {
				return nil, 0, framework.AsStatus(err)
			}
		}
	}

	// No potential victims are found, and so we don't need to evaluate the node again since its state didn't change.
	if len(potentialVictims) == 0 {
		message := fmt.Sprintf("No victims found on node %v for preemptor pod %v", nodeInfo.Node().Name, preemptor.Name)
		return nil, 0, framework.NewStatus(framework.UnschedulableAndUnresolvable, message)
	}

	// If the new pod does not fit after removing all the lower priority pods,
	// we are almost done and this node is not suitable for preemption. The only
	// condition that we could check is if the "pod" is failing to schedule due to
	// inter-pod affinity to one or more victims, but we have decided not to
	// support this case for performance reasons. Having affinity to lower
	// priority pods is not a recommended configuration anyway.
	if status := pl.fh.RunFilterPluginsWithNominatedPods(ctx, state, preemptor, nodeInfo); !status.IsSuccess() {
		return nil, 0, status
	}
	var victims []*v1.Pod
	numViolatingVictim := 0
	sort.Slice(potentialVictims, func(i, j int) bool { return util.MoreImportantPod(potentialVictims[i].Pod, potentialVictims[j].Pod) })
	// Try to reprieve as many pods as possible. We first try to reprieve the PDB
	// violating victims and then other non-violating ones. In both cases, we start
	// from the highest priority victims.
	violatingVictims, nonViolatingVictims := filterPodsWithPDBViolation(potentialVictims, pdbs)
	reprievePod := func(pi *framework.PodInfo) (bool, error) {
		if err := addPod(pi); err != nil {
			return false, err
		}
		status := pl.fh.RunFilterPluginsWithNominatedPods(ctx, state, preemptor, nodeInfo)
		fits := status.IsSuccess()
		if !fits {
			if err := removePod(pi); err != nil {
				return false, err
			}
			rpi := pi.Pod
			victims = append(victims, rpi)
			klog.V(5).InfoS("Pod is a potential preemption victim on node", "pod", klog.KObj(rpi), "node", klog.KObj(nodeInfo.Node()))
		}
		return fits, nil
	}
	for _, p := range violatingVictims {
		if fits, err := reprievePod(p); err != nil {
			return nil, 0, framework.AsStatus(err)
		} else if !fits {
			numViolatingVictim++
		}
	}
	// Now we try to reprieve non-violating victims.
	for _, p := range nonViolatingVictims {
		if _, err := reprievePod(p); err != nil {
			return nil, 0, framework.AsStatus(err)
		}
	}
	return victims, numViolatingVictim, framework.NewStatus(framework.Success)
}