rescale immediately if the basic constraints are not satisfied

pkg/controller/podautoscaler/horizontal.go

@@ -292,9 +292,12 @@ func (a *HorizontalController) reconcileAutoscaler(hpa *autoscaling.HorizontalPo
 	rescaleReason := ""
 	timestamp := time.Now()
 
+	rescale := true
+
 	if scale.Spec.Replicas == 0 {
 		// Autoscaling is disabled for this resource
 		desiredReplicas = 0
+		rescale = false
 	} else if currentReplicas > hpa.Spec.MaxReplicas {
 		rescaleReason = "Current number of replicas above Spec.MaxReplicas"
 		desiredReplicas = hpa.Spec.MaxReplicas
@@ -360,9 +363,10 @@ func (a *HorizontalController) reconcileAutoscaler(hpa *autoscaling.HorizontalPo
 		if desiredReplicas > calculateScaleUpLimit(currentReplicas) {
 			desiredReplicas = calculateScaleUpLimit(currentReplicas)
 		}
+
+		rescale = shouldScale(hpa, currentReplicas, desiredReplicas, timestamp)
 	}
 
-	rescale := shouldScale(hpa, currentReplicas, desiredReplicas, timestamp)
 	if rescale {
 		scale.Spec.Replicas = desiredReplicas
 		_, err = a.scaleNamespacer.Scales(hpa.Namespace).Update(hpa.Spec.ScaleTargetRef.Kind, scale)

pkg/controller/podautoscaler/horizontal_test.go

@@ -96,6 +96,9 @@ type testCase struct {
 
 	// Target resource information.
 	resource *fakeResource
+
+	// Last scale time
+	lastScaleTime *unversioned.Time
 }
 
 // Needs to be called under a lock.
@@ -1043,4 +1046,36 @@ func TestComputedToleranceAlgImplementation(t *testing.T) {
 	tc.runTest(t)
 }
 
+func TestScaleUpRCImmediately(t *testing.T) {
+	time := unversioned.Time{Time: time.Now()}
+	tc := testCase{
+		minReplicas:         2,
+		maxReplicas:         6,
+		initialReplicas:     1,
+		desiredReplicas:     2,
+		verifyCPUCurrent:    true,
+		reportedLevels:      []uint64{0, 0, 0, 0},
+		reportedCPURequests: []resource.Quantity{resource.MustParse("1.0"), resource.MustParse("1.0"), resource.MustParse("1.0"), resource.MustParse("1.0")},
+		useMetricsApi:       true,
+		lastScaleTime:       &time,
+	}
+	tc.runTest(t)
+}
+
+func TestScaleDownRCImmediately(t *testing.T) {
+	time := unversioned.Time{Time: time.Now()}
+	tc := testCase{
+		minReplicas:         2,
+		maxReplicas:         5,
+		initialReplicas:     6,
+		desiredReplicas:     5,
+		CPUTarget:           50,
+		reportedLevels:      []uint64{8000, 9500, 1000},
+		reportedCPURequests: []resource.Quantity{resource.MustParse("0.9"), resource.MustParse("1.0"), resource.MustParse("1.1")},
+		useMetricsApi:       true,
+		lastScaleTime:       &time,
+	}
+	tc.runTest(t)
+}
+
 // TODO: add more tests