Switch to private instances of rand for seeding for tests

Author: liggitt

pkg/scheduler/framework/plugins/defaultpreemption/default_preemption.go

@@ -136,10 +136,14 @@ func (pl *DefaultPreemption) calculateNumCandidates(numNodes int32) int32 {
 	return n
 }
 
+// getOffsetRand is a dedicated random source for GetOffsetAndNumCandidates calls.
+// It defaults to rand.Int31n, but is a package variable so it can be overridden to make unit tests deterministic.
+var getOffsetRand = rand.Int31n
+
 // GetOffsetAndNumCandidates chooses a random offset and calculates the number
 // of candidates that should be shortlisted for dry running preemption.
 func (pl *DefaultPreemption) GetOffsetAndNumCandidates(numNodes int32) (int32, int32) {
-	return rand.Int31n(numNodes), pl.calculateNumCandidates(numNodes)
+	return getOffsetRand(numNodes), pl.calculateNumCandidates(numNodes)
 }
 
 // This function is not applicable for out-of-tree preemption plugins that exercise

pkg/scheduler/framework/plugins/defaultpreemption/default_preemption_test.go

@@ -1197,7 +1197,7 @@ func TestDryRunPreemption(t *testing.T) {
 			// Using 4 as a seed source to test getOffsetAndNumCandidates() deterministically.
 			// However, we need to do it after informerFactory.WaitforCacheSync() which might
 			// set a seed.
-			rand.Seed(4)
+			getOffsetRand = rand.New(rand.NewSource(4)).Int31n
 			var prevNumFilterCalled int32
 			for cycle, pod := range tt.testPods {
 				state := framework.NewCycleState()
@@ -1396,7 +1396,7 @@ func TestSelectBestCandidate(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			rand.Seed(4)
+			getOffsetRand = rand.New(rand.NewSource(4)).Int31n
 			nodes := make([]*v1.Node, len(tt.nodeNames))
 			for i, nodeName := range tt.nodeNames {
 				nodes[i] = st.MakeNode().Name(nodeName).Capacity(veryLargeRes).Obj()

plugin/pkg/auth/authorizer/node/node_authorizer_test.go

@@ -1237,7 +1237,7 @@ func BenchmarkAuthorization(b *testing.B) {
 		},
 	}
 
-	podToAdd, _ := generatePod("testwrite", "ns0", "node0", "default", opts)
+	podToAdd, _ := generatePod("testwrite", "ns0", "node0", "default", opts, rand.Perm)
 
 	b.ResetTimer()
 	for _, testWriteContention := range []bool{false, true} {
@@ -1338,11 +1338,11 @@ func populate(graph *Graph, nodes []*corev1.Node, pods []*corev1.Pod, pvs []*cor
 	}
 }
 
-func randomSubset(a, b int) []int {
+func randomSubset(a, b int, randPerm func(int) []int) []int {
 	if b < a {
 		b = a
 	}
-	return rand.Perm(b)[:a]
+	return randPerm(b)[:a]
 }
 
 // generate creates sample pods and persistent volumes based on the provided options.
@@ -1356,7 +1356,7 @@ func generate(opts *sampleDataOpts) ([]*corev1.Node, []*corev1.Pod, []*corev1.Pe
 	attachments := make([]*storagev1.VolumeAttachment, 0, opts.nodes*opts.attachmentsPerNode)
 	slices := make([]*resourceapi.ResourceSlice, 0, opts.nodes*opts.nodeResourceSlicesPerNode)
 
-	rand.Seed(12345)
+	r := rand.New(rand.NewSource(12345))
 
 	for n := 0; n < opts.nodes; n++ {
 		nodeName := fmt.Sprintf("node%d", n)
@@ -1365,7 +1365,7 @@ func generate(opts *sampleDataOpts) ([]*corev1.Node, []*corev1.Pod, []*corev1.Pe
 			namespace := fmt.Sprintf("ns%d", p%opts.namespaces)
 			svcAccountName := fmt.Sprintf("svcacct%d-%s", p, nodeName)
 
-			pod, podPVs := generatePod(name, namespace, nodeName, svcAccountName, opts)
+			pod, podPVs := generatePod(name, namespace, nodeName, svcAccountName, opts, r.Perm)
 			pods = append(pods, pod)
 			pvs = append(pvs, podPVs...)
 		}
@@ -1395,7 +1395,7 @@ func generate(opts *sampleDataOpts) ([]*corev1.Node, []*corev1.Pod, []*corev1.Pe
 	return nodes, pods, pvs, attachments, slices
 }
 
-func generatePod(name, namespace, nodeName, svcAccountName string, opts *sampleDataOpts) (*corev1.Pod, []*corev1.PersistentVolume) {
+func generatePod(name, namespace, nodeName, svcAccountName string, opts *sampleDataOpts, randPerm func(int) []int) (*corev1.Pod, []*corev1.PersistentVolume) {
 	pvs := make([]*corev1.PersistentVolume, 0, opts.uniquePVCsPerPod+opts.sharedPVCsPerPod)
 
 	pod := &corev1.Pod{}
@@ -1410,7 +1410,7 @@ func generatePod(name, namespace, nodeName, svcAccountName string, opts *sampleD
 		}})
 	}
 	// Choose shared secrets randomly from shared secrets in a namespace.
-	subset := randomSubset(opts.sharedSecretsPerPod, opts.sharedSecretsPerNamespace)
+	subset := randomSubset(opts.sharedSecretsPerPod, opts.sharedSecretsPerNamespace, randPerm)
 	for _, i := range subset {
 		pod.Spec.Volumes = append(pod.Spec.Volumes, corev1.Volume{VolumeSource: corev1.VolumeSource{
 			Secret: &corev1.SecretVolumeSource{SecretName: fmt.Sprintf("secret%d-shared", i)},
@@ -1423,7 +1423,7 @@ func generatePod(name, namespace, nodeName, svcAccountName string, opts *sampleD
 		}})
 	}
 	// Choose shared configmaps randomly from shared configmaps in a namespace.
-	subset = randomSubset(opts.sharedConfigMapsPerPod, opts.sharedConfigMapsPerNamespace)
+	subset = randomSubset(opts.sharedConfigMapsPerPod, opts.sharedConfigMapsPerNamespace, randPerm)
 	for _, i := range subset {
 		pod.Spec.Volumes = append(pod.Spec.Volumes, corev1.Volume{VolumeSource: corev1.VolumeSource{
 			ConfigMap: &corev1.ConfigMapVolumeSource{LocalObjectReference: corev1.LocalObjectReference{Name: fmt.Sprintf("configmap%d-shared", i)}},
@@ -1470,7 +1470,7 @@ func generatePod(name, namespace, nodeName, svcAccountName string, opts *sampleD
 		})
 	}
 	// Choose shared pvcs randomly from shared pvcs in a namespace.
-	subset = randomSubset(opts.sharedPVCsPerPod, opts.sharedPVCsPerNamespace)
+	subset = randomSubset(opts.sharedPVCsPerPod, opts.sharedPVCsPerNamespace, randPerm)
 	for _, i := range subset {
 		pv := &corev1.PersistentVolume{}
 		pv.Name = fmt.Sprintf("pv%d-shared-%s", i, pod.Namespace)

staging/src/k8s.io/apimachinery/pkg/util/rand/rand_test.go

@@ -65,10 +65,10 @@ func TestIntn(t *testing.T) {
 
 func TestPerm(t *testing.T) {
 	Seed(5)
-	rand.Seed(5)
+	r := rand.New(rand.NewSource(5))
 	for i := 1; i < 20; i++ {
 		actual := Perm(i)
-		expected := rand.Perm(i)
+		expected := r.Perm(i)
 		for j := 0; j < i; j++ {
 			if actual[j] != expected[j] {
 				t.Errorf("Perm call result is unexpected")

staging/src/k8s.io/apimachinery/pkg/util/wait/wait.go

@@ -80,6 +80,10 @@ func Forever(f func(), period time.Duration) {
 	Until(f, period, NeverStop)
 }
 
+// jitterRand is a dedicated random source for jitter calculations.
+// It defaults to rand.Float64, but is a package variable so it can be overridden to make unit tests deterministic.
+var jitterRand = rand.Float64
+
 // Jitter returns a time.Duration between duration and duration + maxFactor *
 // duration.
 //
@@ -89,7 +93,7 @@ func Jitter(duration time.Duration, maxFactor float64) time.Duration {
 	if maxFactor <= 0.0 {
 		maxFactor = 1.0
 	}
-	wait := duration + time.Duration(rand.Float64()*maxFactor*float64(duration))
+	wait := duration + time.Duration(jitterRand()*maxFactor*float64(duration))
 	return wait
 }
 

staging/src/k8s.io/apimachinery/pkg/util/wait/wait_test.go

@@ -682,7 +682,7 @@ func TestBackoff_Step(t *testing.T) {
 				initial = nil
 			}
 			t.Run(fmt.Sprintf("%#v seed=%d", initial, seed), func(t *testing.T) {
-				rand.Seed(seed)
+				jitterRand = rand.New(rand.NewSource(seed)).Float64
 				for i := 0; i < len(tt.want); i++ {
 					got := initial.Step()
 					t.Logf("[%d]=%s", i, got)

test/e2e/storage/utils/utils.go

@@ -490,9 +490,9 @@ func readFile(content, path string) string {
 // genBinDataFromSeed generate binData with random seed
 func genBinDataFromSeed(len int, seed int64) []byte {
 	binData := make([]byte, len)
-	rand.Seed(seed)
+	r := rand.New(rand.NewSource(seed))
 
-	_, err := rand.Read(binData)
+	_, err := r.Read(binData)
 	if err != nil {
 		fmt.Printf("Error: %v\n", err)
 	}