improve TestParallelScale test

we can test for larger number of parallel requests than 2 in statefulsets with hundreds of replicas

Author: atiratree

pkg/controller/statefulset/stateful_set_control_test.go

@@ -20,6 +20,7 @@ import (
 "context"
 "errors"
 "fmt"
+"math"
 "math/rand"
 "reflect"
 "runtime"
@@ -2940,47 +2941,57 @@ func fakeResourceVersion(object interface{}) {
 obj.SetResourceVersion(strconv.FormatInt(intValue+1, 10))
 }
 }
-
 func TestParallelScale(t *testing.T) {
 for _, tc := range []struct {
-desc string
-replicas int32
-desiredReplicas int32
+desc string
+replicas int32
+desiredReplicas int32
+expectedMinParallelRequests int
 }{
 {
-desc: "scale up from 3 to 30",
-replicas: 3,
-desiredReplicas: 30,
+desc: "scale up from 3 to 30",
+replicas: 3,
+desiredReplicas: 30,
+expectedMinParallelRequests: 2,
 },
 {
-desc: "scale down from 10 to 1",
-replicas: 10,
-desiredReplicas: 1,
+desc: "scale down from 10 to 1",
+replicas: 10,
+desiredReplicas: 1,
+expectedMinParallelRequests: 2,
 },
 
 {
-desc: "scale down to 0",
-replicas: 501,
-desiredReplicas: 0,
+desc: "scale down to 0",
+replicas: 501,
+desiredReplicas: 0,
+expectedMinParallelRequests: 10,
 },
 {
-desc: "scale up from 0",
-replicas: 0,
-desiredReplicas: 1000,
+desc: "scale up from 0",
+replicas: 0,
+desiredReplicas: 1000,
+expectedMinParallelRequests: 20,
 },
 } {
 t.Run(tc.desc, func(t *testing.T) {
 set := burst(newStatefulSet(0))
 set.Spec.VolumeClaimTemplates[0].ObjectMeta.Labels = map[string]string{"test": "test"}
-parallelScale(t, set, tc.replicas, tc.desiredReplicas, assertBurstInvariants)
+parallelScale(t, set, tc.replicas, tc.desiredReplicas, tc.expectedMinParallelRequests, assertBurstInvariants)
 })
 }
 
 }
 
-func parallelScale(t *testing.T, set *apps.StatefulSet, replicas, desiredReplicas int32, invariants invariantFunc) {
+func parallelScale(t *testing.T, set *apps.StatefulSet, replicas, desiredReplicas int32, expectedMinParallelRequests int, invariants invariantFunc) {
 var err error
 diff := desiredReplicas - replicas
+
+// maxParallelRequests: MaxBatchSize of the controller is 500, We divide the diff by 4 to allow maximum of the half of the last batch.
+if maxParallelRequests := min(500, math.Abs(float64(diff))/4); expectedMinParallelRequests < 2 || float64(expectedMinParallelRequests) > maxParallelRequests {
+t.Fatalf("expectedMinParallelRequests should be between 2 and %v. Batch size of the controller is expontially increasing until 500. "+
+"Got expectedMinParallelRequests %v, ", maxParallelRequests, expectedMinParallelRequests)
+}
 client := fake.NewSimpleClientset(set)
 om, _, ssc := setupController(client)
 om.createPodTracker.shouldTrackParallelRequests = true
@@ -3016,8 +3027,8 @@ func parallelScale(t *testing.T, set *apps.StatefulSet, replicas, desiredReplica
 t.Errorf("Failed to scale statefulset to %v replicas, got %v replicas", desiredReplicas, set.Status.Replicas)
 }
 
-if (diff < -1 || diff > 1) && om.createPodTracker.maxParallelRequests <= 1 {
-t.Errorf("want max parallel requests > 1, got %v", om.createPodTracker.maxParallelRequests)
+if om.createPodTracker.maxParallelRequests < expectedMinParallelRequests {
+t.Errorf("want max parallelRequests requests >= %v, got %v", expectedMinParallelRequests, om.createPodTracker.maxParallelRequests)
 }
 }