Support percentages in rollout-max-unavailable annotation

CHANGELOG.md

@@ -7,6 +7,7 @@
   * The boringcrypto base image is now `gcr.io/distroless/base-nossl-debian12:nonroot` (for glibc).
 * [ENHANCEMENT] Include unique IDs of webhook requests in logs for easier debugging. #150
 * [ENHANCEMENT] Include k8s operation username in request debug logs. #152
+* [ENHANCEMENT] `rollout-max-unavailable` annotation can now be specified as percentage, e.g.: `rollout-max-unavailable: 25%`. Resulting value is computed as `floor(replicas * percentage)`, but is never less than 1. #153
 
 ## v0.16.0
 

pkg/controller/labels.go

@@ -2,7 +2,9 @@ package controller
 
 import (
 	"fmt"
+	"math"
 	"strconv"
+	"strings"
 
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
@@ -21,10 +23,35 @@ func getMaxUnavailableForStatefulSet(sts *v1.StatefulSet, logger log.Logger) int
 		return 1
 	}
 
+	rawValue = strings.TrimSpace(rawValue)
+
+	if strings.HasSuffix(rawValue, "%") {
+		perc, err := strconv.Atoi(rawValue[:len(rawValue)-1])
+
+		if err != nil || perc <= 0 || perc > 100 {
+			level.Error(logger).Log(
+				"msg", fmt.Sprintf("StatefulSet has invalid %s annotation (expected positive integer or percentage as integer%%)", config.RolloutMaxUnavailableAnnotationKey),
+				"statefulset", sts.Name,
+				"value", rawValue)
+
+			return 1
+		}
+
+		if sts.Spec.Replicas == nil {
+			return 1
+		}
+
+		result := int(math.Floor(float64(perc*int(*sts.Spec.Replicas)) / 100))
+		if result < 1 {
+			result = 1
+		}
+		return result
+	}
+
 	value, err := strconv.Atoi(rawValue)
 	if err != nil || value <= 0 {
 		level.Error(logger).Log(
-			"msg", fmt.Sprintf("StatefulSet has invalid %s annotation (expected positive integer)", config.RolloutMaxUnavailableAnnotationKey),
+			"msg", fmt.Sprintf("StatefulSet has invalid %s annotation (expected positive integer or percentage as integer%%)", config.RolloutMaxUnavailableAnnotationKey),
 			"statefulset", sts.Name,
 			"value", rawValue)
 

pkg/controller/labels_test.go

@@ -60,11 +60,83 @@ func TestGetMaxUnavailableForStatefulSet(t *testing.T) {
 			},
 			expected: 1,
 		},
-	}
+		"should return percentage of statefulset replicas, if annotation uses percentage": {
+			sts: &v1.StatefulSet{
+				Spec: v1.StatefulSetSpec{
+					Replicas: intPointer(10),
+				},
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{
+						config.RolloutMaxUnavailableAnnotationKey: "30%",
+					},
+				},
+			},
+			expected: 3,
+		},
+		"should return floor percentage of statefulset replicas, if annotation uses percentage": {
+			sts: &v1.StatefulSet{
+				Spec: v1.StatefulSetSpec{
+					Replicas: intPointer(10),
+				},
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{
+						config.RolloutMaxUnavailableAnnotationKey: "25%",
+					},
+				},
+			},
+			expected: 2,
+		},
+		"should return floor percentage of statefulset replicas, if annotation uses percentage, 3 replicas": {
+			sts: &v1.StatefulSet{
+				Spec: v1.StatefulSetSpec{
+					Replicas: intPointer(3),
+				},
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{
+						config.RolloutMaxUnavailableAnnotationKey: "50%",
+					},
+				},
+			},
+			expected: 1,
+		},
+		"should return 1 of statefulset replicas, if annotation uses percentage, but statefulset doesn't have replicas": {
+			sts: &v1.StatefulSet{
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{
+						config.RolloutMaxUnavailableAnnotationKey: "30%",
+					},
+				},
+			},
+			expected: 1,
+		},
+		"should return 1 of statefulset replicas, if annotation uses percentage, but values is too high": {
+			sts: &v1.StatefulSet{
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{
+						config.RolloutMaxUnavailableAnnotationKey: "300%",
+					},
+				},
+			},
+			expected: 1,
+		},
+		"should return 1 of statefulset replicas, if annotation uses percentage, but values is too low": {
+			sts: &v1.StatefulSet{
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{
+						config.RolloutMaxUnavailableAnnotationKey: "0%",
+					},
+				},
+			},
+			expected: 1,
+		}}
 
 	for testName, testCase := range tests {
 		t.Run(testName, func(t *testing.T) {
 			assert.Equal(t, testCase.expected, getMaxUnavailableForStatefulSet(testCase.sts, log.NewNopLogger()))
 		})
 	}
 }
+
+func intPointer(i int32) *int32 {
+	return &i
+}