Deployment: preserve availability when maxUnavailability is not 100%

pkg/controller/deployment/deployment_controller.go

@@ -847,7 +847,7 @@ func (dc *DeploymentController) reconcileOldReplicaSets(allRSs []*extensions.Rep
 		return false, fmt.Errorf("could not find available pods: %v", err)
 	}
 
-	maxUnavailable, err := intstrutil.GetValueFromIntOrPercent(&deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, deployment.Spec.Replicas)
+	maxUnavailable, err := intstrutil.GetValueFromIntOrPercent(&deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, deployment.Spec.Replicas, false)
 	if err != nil {
 		return false, err
 	}
@@ -948,7 +948,7 @@ func (dc *DeploymentController) cleanupUnhealthyReplicas(oldRSs []*extensions.Re
 // scaleDownOldReplicaSetsForRollingUpdate scales down old replica sets when deployment strategy is "RollingUpdate".
 // Need check maxUnavailable to ensure availability
 func (dc *DeploymentController) scaleDownOldReplicaSetsForRollingUpdate(allRSs []*extensions.ReplicaSet, oldRSs []*extensions.ReplicaSet, deployment extensions.Deployment) (int, error) {
-	maxUnavailable, err := intstrutil.GetValueFromIntOrPercent(&deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, deployment.Spec.Replicas)
+	maxUnavailable, err := intstrutil.GetValueFromIntOrPercent(&deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, deployment.Spec.Replicas, false)
 	if err != nil {
 		return 0, err
 	}

pkg/util/deployment/deployment.go

@@ -420,7 +420,7 @@ func NewRSNewReplicas(deployment *extensions.Deployment, allRSs []*extensions.Re
 	switch deployment.Spec.Strategy.Type {
 	case extensions.RollingUpdateDeploymentStrategyType:
 		// Check if we can scale up.
-		maxSurge, err := intstrutil.GetValueFromIntOrPercent(&deployment.Spec.Strategy.RollingUpdate.MaxSurge, deployment.Spec.Replicas)
+		maxSurge, err := intstrutil.GetValueFromIntOrPercent(&deployment.Spec.Strategy.RollingUpdate.MaxSurge, deployment.Spec.Replicas, true)
 		if err != nil {
 			return 0, err
 		}

pkg/util/intstr/intstr.go

@@ -116,13 +116,17 @@ func (intstr *IntOrString) Fuzz(c fuzz.Continue) {
 	}
 }
 
-func GetValueFromIntOrPercent(intOrPercent *IntOrString, total int) (int, error) {
+func GetValueFromIntOrPercent(intOrPercent *IntOrString, total int, roundUp bool) (int, error) {
 	value, isPercent, err := getIntOrPercentValue(intOrPercent)
 	if err != nil {
 		return 0, fmt.Errorf("invalid value for IntOrString: %v", err)
 	}
 	if isPercent {
-		value = int(math.Ceil(float64(value) * (float64(total)) / 100))
+		if roundUp {
+			value = int(math.Ceil(float64(value) * (float64(total)) / 100))
+		} else {
+			value = int(math.Floor(float64(value) * (float64(total)) / 100))
+		}
 	}
 	return value, nil
 }

pkg/util/intstr/intstr_test.go

@@ -114,6 +114,7 @@ func TestGetValueFromIntOrPercent(t *testing.T) {
 	tests := []struct {
 		input     IntOrString
 		total     int
+		roundUp   bool
 		expectErr bool
 		expectVal int
 	}{
@@ -125,9 +126,24 @@ func TestGetValueFromIntOrPercent(t *testing.T) {
 		{
 			input:     FromString("90%"),
 			total:     100,
+			roundUp:   true,
 			expectErr: false,
 			expectVal: 90,
 		},
+		{
+			input:     FromString("90%"),
+			total:     95,
+			roundUp:   true,
+			expectErr: false,
+			expectVal: 86,
+		},
+		{
+			input:     FromString("90%"),
+			total:     95,
+			roundUp:   false,
+			expectErr: false,
+			expectVal: 85,
+		},
 		{
 			input:     FromString("%"),
 			expectErr: true,
@@ -144,7 +160,7 @@ func TestGetValueFromIntOrPercent(t *testing.T) {
 
 	for i, test := range tests {
 		t.Logf("test case %d", i)
-		value, err := GetValueFromIntOrPercent(&test.input, test.total)
+		value, err := GetValueFromIntOrPercent(&test.input, test.total, test.roundUp)
 		if test.expectErr && err == nil {
 			t.Errorf("expected error, but got none")
 			continue
@@ -154,7 +170,7 @@ func TestGetValueFromIntOrPercent(t *testing.T) {
 			continue
 		}
 		if test.expectVal != value {
-			t.Errorf("expected %v, but got %v", test.expectErr, value)
+			t.Errorf("expected %v, but got %v", test.expectVal, value)
 		}
 	}
 }