clean up the implementation around QueueingHintFn

pkg/scheduler/framework/runtime/framework.go

@@ -551,17 +551,7 @@ func (p *defaultEnqueueExtension) EventsToRegister() []framework.ClusterEventWit
 	// because the returning values are used to register event handlers.
 	// If we return the wildcard here, it won't affect the event handlers registered by the plugin
 	// and some events may not be registered in the event handlers.
-	return []framework.ClusterEventWithHint{
-		{Event: framework.ClusterEvent{Resource: framework.Pod, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.Node, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.CSINode, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.CSIDriver, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.CSIStorageCapacity, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.PersistentVolume, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.PersistentVolumeClaim, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.StorageClass, ActionType: framework.All}},
-		{Event: framework.ClusterEvent{Resource: framework.PodSchedulingContext, ActionType: framework.All}},
-	}
+	return framework.UnrollWildCardResource()
 }
 
 func updatePluginList(pluginList interface{}, pluginSet config.PluginSet, pluginsMap map[string]framework.Plugin) error {

pkg/scheduler/framework/types.go

@@ -107,7 +107,7 @@ const (
 	QueueSkip QueueingHint = iota
 
 	// QueueAfterBackoff implies that the Pod may be schedulable by the event,
-	// and worth retring the scheduling again after backoff.
+	// and worth retrying the scheduling again after backoff.
 	QueueAfterBackoff
 
 	// QueueImmediately is returned only when it is highly possible that the Pod gets scheduled in the next scheduling.
@@ -147,6 +147,20 @@ func (ce ClusterEvent) IsWildCard() bool {
 	return ce.Resource == WildCard && ce.ActionType == All
 }
 
+func UnrollWildCardResource() []ClusterEventWithHint {
+	return []ClusterEventWithHint{
+		{Event: ClusterEvent{Resource: Pod, ActionType: All}},
+		{Event: ClusterEvent{Resource: Node, ActionType: All}},
+		{Event: ClusterEvent{Resource: CSINode, ActionType: All}},
+		{Event: ClusterEvent{Resource: CSIDriver, ActionType: All}},
+		{Event: ClusterEvent{Resource: CSIStorageCapacity, ActionType: All}},
+		{Event: ClusterEvent{Resource: PersistentVolume, ActionType: All}},
+		{Event: ClusterEvent{Resource: PersistentVolumeClaim, ActionType: All}},
+		{Event: ClusterEvent{Resource: StorageClass, ActionType: All}},
+		{Event: ClusterEvent{Resource: PodSchedulingContext, ActionType: All}},
+	}
+}
+
 // QueuedPodInfo is a Pod wrapper with additional information related to
 // the pod's status in the scheduling queue, such as the timestamp when
 // it's added to the queue.

pkg/scheduler/internal/queue/scheduling_queue.go

@@ -389,18 +389,17 @@ func (p *PriorityQueue) isPodWorthRequeuing(logger klog.Logger, pInfo *framework
 				continue
 			}
 
-			h := hintfn.QueueingHintFn(pod, oldObj, newObj)
-			if h == framework.QueueSkip {
+			switch h := hintfn.QueueingHintFn(pod, oldObj, newObj); h {
+			case framework.QueueSkip:
 				continue
-			}
-
-			if h == framework.QueueImmediately {
+			case framework.QueueImmediately:
 				return h
+			case framework.QueueAfterBackoff:
+				// replace queueHint with the returned value,
+				// but continue to other queueHintFn to check because other plugins may want to return QueueImmediately.
+				queueHint = h
 			}
 
-			// replace queueHint with the returned value,
-			// but continue to other queueHintFn to check because other plugins may want to return QueueImmediately.
-			queueHint = h
 		}
 	}
 
@@ -855,7 +854,7 @@ func (p *PriorityQueue) requeuePodViaQueueingHint(logger klog.Logger, pInfo *fra
 	}
 
 	pod := pInfo.Pod
-	if p.isPodBackingoff(pInfo) && schedulingHint == framework.QueueAfterBackoff {
+	if schedulingHint == framework.QueueAfterBackoff && p.isPodBackingoff(pInfo) {
 		if err := p.podBackoffQ.Add(pInfo); err != nil {
 			logger.Error(err, "Error adding pod to the backoff queue, queue this Pod to unschedulable pod pool", "pod", klog.KObj(pod))
 			p.unschedulablePods.addOrUpdate(pInfo)
@@ -866,10 +865,20 @@ func (p *PriorityQueue) requeuePodViaQueueingHint(logger klog.Logger, pInfo *fra
 		return backoffQ
 	}
 
-	if added, _ := p.addToActiveQ(logger, pInfo); added {
+	// Reach here if schedulingHint is QueueImmediately, or schedulingHint is QueueAfterBackoff but the pod is not backing off.
+
+	added, err := p.addToActiveQ(logger, pInfo)
+	if err != nil {
+		logger.Error(err, "Error adding pod to the active queue, queue this Pod to unschedulable pod pool", "pod", klog.KObj(pod))
+	}
+	if added {
 		metrics.SchedulerQueueIncomingPods.WithLabelValues("active", event).Inc()
 		return activeQ
 	}
+	if pInfo.Gated {
+		// In case the pod is gated, the Pod is pushed back to unschedulable Pods pool in addToActiveQ.
+		return unschedulablePods
+	}
 
 	p.unschedulablePods.addOrUpdate(pInfo)
 	metrics.SchedulerQueueIncomingPods.WithLabelValues("unschedulable", ScheduleAttemptFailure).Inc()

pkg/scheduler/scheduler.go

@@ -366,9 +366,15 @@ var defaultQueueingHintFn = func(_ *v1.Pod, _, _ interface{}) framework.Queueing
 }
 
 func buildQueueingHintMap(es []framework.EnqueueExtensions) internalqueue.QueueingHintMap {
-	queueingHintMap := make(map[framework.ClusterEvent][]*internalqueue.QueueingHintFunction)
+	queueingHintMap := make(internalqueue.QueueingHintMap)
 	for _, e := range es {
 		events := e.EventsToRegister()
+
+		// Note: Rarely, a plugin implements EnqueueExtensions but returns nil.
+		// We treat it as: the plugin is not interested in any event, and hence pod failed by that plugin
+		// cannot be moved by any regular cluster event.
+		// So, we can just ignore such EventsToRegister here.
+
 		for _, event := range events {
 			fn := event.QueueingHintFn
 			if fn == nil {

pkg/scheduler/scheduler_test.go

@@ -657,10 +657,9 @@ const (
 
 func Test_buildQueueingHintMap(t *testing.T) {
 	tests := []struct {
-		name     string
-		plugins  []framework.Plugin
-		want     map[framework.ClusterEvent][]*internalqueue.QueueingHintFunction
-		assertFn func(t *testing.T, got map[framework.ClusterEvent][]*internalqueue.QueueingHintFunction) bool
+		name    string
+		plugins []framework.Plugin
+		want    map[framework.ClusterEvent][]*internalqueue.QueueingHintFunction
 	}{
 		{
 			name:    "no-op plugin",