fix: flaky TestPrepareCandidate

pkg/scheduler/framework/preemption/preemption_test.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"reflect"
 	"sort"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -446,7 +447,11 @@ func TestPrepareCandidate(t *testing.T) {
 		candidate *fakeCandidate
 		preemptor *v1.Pod
 		testPods  []*v1.Pod
-		expectedDeletedPods   []string
+		// expectedDeletedPod is the pod name that is expected to be deleted.
+		//
+		// You can set multiple pod name if there're multiple possibilities.
+		// Both empty and "" means no pod is expected to be deleted.
+		expectedDeletedPod    []string
 		expectedDeletionError bool
 		expectedPatchError    bool
 		// Only compared when async preemption is disabled.
@@ -457,7 +462,6 @@ func TestPrepareCandidate(t *testing.T) {
 	}{
 		{
 			name: "no victims",
-
 			candidate: &fakeCandidate{
 				victims: &extenderv1.Victims{},
 			},
@@ -485,7 +489,7 @@ func TestPrepareCandidate(t *testing.T) {
 				victim1,
 			},
 			nodeNames:             []string{node1Name},
-			expectedDeletedPods:   []string{"victim1"},
+			expectedDeletedPod:    []string{"victim1"},
 			expectedStatus:        nil,
 			expectedPreemptingMap: sets.New(types.UID("preemptor")),
 		},
@@ -505,7 +509,7 @@ func TestPrepareCandidate(t *testing.T) {
 				victim1WithMatchingCondition,
 			},
 			nodeNames:             []string{node1Name},
-			expectedDeletedPods:   []string{"victim1"},
+			expectedDeletedPod:    []string{"victim1"},
 			expectedStatus:        nil,
 			expectedPreemptingMap: sets.New(types.UID("preemptor")),
 		},
@@ -523,7 +527,7 @@ func TestPrepareCandidate(t *testing.T) {
 			preemptor:             preemptor,
 			testPods:              []*v1.Pod{},
 			nodeNames:             []string{node1Name},
-			expectedDeletedPods:   []string{"victim1"},
+			expectedDeletedPod:    []string{"victim1"},
 			expectedStatus:        nil,
 			expectedPreemptingMap: sets.New(types.UID("preemptor")),
 		},
@@ -560,7 +564,7 @@ func TestPrepareCandidate(t *testing.T) {
 			preemptor:             preemptor,
 			testPods:              []*v1.Pod{},
 			nodeNames:             []string{node1Name},
-			expectedDeletedPods:   []string{"victim1"},
+			expectedDeletedPod:    []string{"victim1"},
 			expectedStatus:        nil,
 			expectedPreemptingMap: sets.New(types.UID("preemptor")),
 		},
@@ -601,7 +605,12 @@ func TestPrepareCandidate(t *testing.T) {
 			},
 			nodeNames:          []string{node1Name},
 			expectedPatchError: true,
-			expectedDeletedPods:   []string{"victim2"},
+			expectedDeletedPod: []string{
+				"victim2",
+				// The first victim could fail before the deletion of the second victim happens,
+				// which results in the second victim not being deleted.
+				"",
+			},
 			expectedStatus:        framework.AsStatus(errors.New("patch pod status failed")),
 			expectedPreemptingMap: sets.New(types.UID("preemptor")),
 			expectedActivatedPods: map[string]*v1.Pod{preemptor.Name: preemptor},
@@ -629,7 +638,6 @@ func TestPrepareCandidate(t *testing.T) {
 					objs = append(objs, pod)
 				}
 
-				requestStopper := make(chan struct{})
 				mu := &sync.RWMutex{}
 				deletedPods := sets.New[string]()
 				deletionFailure := false // whether any request to delete pod failed
@@ -637,7 +645,6 @@ func TestPrepareCandidate(t *testing.T) {
 
 				cs := clientsetfake.NewClientset(objs...)
 				cs.PrependReactor("delete", "pods", func(action clienttesting.Action) (bool, runtime.Object, error) {
-					<-requestStopper
 					mu.Lock()
 					defer mu.Unlock()
 					name := action.(clienttesting.DeleteAction).GetName()
@@ -651,7 +658,6 @@ func TestPrepareCandidate(t *testing.T) {
 				})
 
 				cs.PrependReactor("patch", "pods", func(action clienttesting.Action) (bool, runtime.Object, error) {
-					<-requestStopper
 					mu.Lock()
 					defer mu.Unlock()
 					if action.(clienttesting.PatchAction).GetName() == "fail-victim" {
@@ -664,6 +670,15 @@ func TestPrepareCandidate(t *testing.T) {
 				informerFactory := informers.NewSharedInformerFactory(cs, 0)
 				eventBroadcaster := events.NewBroadcaster(&events.EventSinkImpl{Interface: cs.EventsV1()})
 				fakeActivator := &fakePodActivator{activatedPods: make(map[string]*v1.Pod), mu: mu}
+
+				// Note: NominatedPodsForNode is called at the beginning of the goroutine in any case.
+				// fakePodNominator can delay the response of NominatedPodsForNode until the channel is closed,
+				// which allows us to test the preempting map before the goroutine does nothing yet.
+				requestStopper := make(chan struct{})
+				nominator := &fakePodNominator{
+					SchedulingQueue: internalqueue.NewSchedulingQueue(nil, informerFactory),
+					requestStopper:  requestStopper,
+				}
 				fwk, err := tf.NewFramework(
 					ctx,
 					registeredPlugins, "",
@@ -672,7 +687,7 @@ func TestPrepareCandidate(t *testing.T) {
 					frameworkruntime.WithInformerFactory(informerFactory),
 					frameworkruntime.WithWaitingPods(frameworkruntime.NewWaitingPodsMap()),
 					frameworkruntime.WithSnapshotSharedLister(internalcache.NewSnapshot(tt.testPods, nodes)),
-					frameworkruntime.WithPodNominator(internalqueue.NewSchedulingQueue(nil, informerFactory)),
+					frameworkruntime.WithPodNominator(nominator),
 					frameworkruntime.WithEventRecorder(eventBroadcaster.NewRecorder(scheme.Scheme, "test-scheduler")),
 					frameworkruntime.WithPodActivator(fakeActivator),
 				)
@@ -720,10 +735,15 @@ func TestPrepareCandidate(t *testing.T) {
 				if err := wait.PollUntilContextTimeout(ctx, time.Millisecond*200, wait.ForeverTestTimeout, false, func(ctx context.Context) (bool, error) {
 					mu.RLock()
 					defer mu.RUnlock()
-					if !deletedPods.Equal(sets.New(tt.expectedDeletedPods...)) {
+
-						lastErrMsg = fmt.Sprintf("expected deleted pods %v, got %v", tt.expectedDeletedPods, deletedPods.UnsortedList())
+					pe.mu.Lock()
+					defer pe.mu.Unlock()
+					if len(pe.preempting) != 0 {
+						// The preempting map should be empty after the goroutine in all test cases.
+						lastErrMsg = fmt.Sprintf("expected no preempting pods, got %v", pe.preempting)
 						return false, nil
 					}
+
 					if tt.expectedDeletionError != deletionFailure {
 						lastErrMsg = fmt.Sprintf("expected deletion error %v, got %v", tt.expectedDeletionError, deletionFailure)
 						return false, nil
@@ -744,6 +764,34 @@ func TestPrepareCandidate(t *testing.T) {
 						}
 					}
 
+					if deletedPods.Len() > 1 {
+						// For now, we only expect at most one pod to be deleted in all test cases.
+						// If we need to test multiple pods deletion, we need to update the test table definition.
+						return false, fmt.Errorf("expected at most one pod to be deleted, got %v", deletedPods.UnsortedList())
+					}
+
+					if len(tt.expectedDeletedPod) == 0 {
+						if deletedPods.Len() != 0 {
+							// When tt.expectedDeletedPod is empty, we expect no pod to be deleted.
+							return false, fmt.Errorf("expected no pod to be deleted, got %v", deletedPods.UnsortedList())
+						}
+						// nothing further to check.
+						return true, nil
+					}
+
+					found := false
+					for _, podName := range tt.expectedDeletedPod {
+						if deletedPods.Has(podName) ||
+							// If podName is empty, we expect no pod to be deleted.
+							(deletedPods.Len() == 0 && podName == "") {
+							found = true
+						}
+					}
+					if !found {
+						lastErrMsg = fmt.Sprintf("expected pod %v to be deleted, but %v is deleted", strings.Join(tt.expectedDeletedPod, " or "), deletedPods.UnsortedList())
+						return false, nil
+					}
+
 					return true, nil
 				}); err != nil {
 					t.Fatal(lastErrMsg)
@@ -753,6 +801,19 @@ func TestPrepareCandidate(t *testing.T) {
 	}
 }
 
+type fakePodNominator struct {
+	// embed it so that we can only override NominatedPodsForNode
+	internalqueue.SchedulingQueue
+
+	// fakePodNominator doesn't respond to NominatedPodsForNode() until the channel is closed.
+	requestStopper chan struct{}
+}
+
+func (f *fakePodNominator) NominatedPodsForNode(nodeName string) []*framework.PodInfo {
+	<-f.requestStopper
+	return nil
+}
+
 type fakeExtender struct {
 	ignorable            bool
 	errProcessPreemption bool