fix: ensure the machineset label value is valid per K8s convention

harvester/create.go

@@ -53,9 +53,12 @@ func (d *Driver) Create() error {
 		//with this unique machine set. This can then be used for populating affinity rules
 		machineSetSplit := strings.Split(d.MachineName, "-")
 		machineSetSplit = append([]string{d.VMNamespace}, machineSetSplit...)
-		machineSetName := strings.Join(machineSetSplit[:len(machineSetSplit)-2], "-")
+		machineSetName, err := formatLabelValue(strings.Join(machineSetSplit[:len(machineSetSplit)-2], "-"))
+		if err != nil {
+			return err
+		}
 		vmBuilder = vmBuilder.Labels(map[string]string{poolNameLabelKey: machineSetName})
-		addtionalPodAffinityTerm := corev1.PodAffinityTerm{
+		additionalPodAffinityTerm := corev1.PodAffinityTerm{
 			LabelSelector: &metav1.LabelSelector{
 				MatchLabels: map[string]string{
 					poolNameLabelKey: machineSetName,
@@ -65,7 +68,7 @@ func (d *Driver) Create() error {
 		}
 		additionalWeightPodAffinity := corev1.WeightedPodAffinityTerm{
 			Weight:          1,
-			PodAffinityTerm: addtionalPodAffinityTerm,
+			PodAffinityTerm: additionalPodAffinityTerm,
 		}
 		if affinity.PodAffinity != nil {
 			affinity.PodAffinity.PreferredDuringSchedulingIgnoredDuringExecution = append(affinity.PodAffinity.PreferredDuringSchedulingIgnoredDuringExecution, additionalWeightPodAffinity)

harvester/labels.go

@@ -0,0 +1,32 @@
+package harvester
+
+import (
+	"encoding/base64"
+	"fmt"
+	"hash/fnv"
+
+	"k8s.io/apimachinery/pkg/util/validation"
+)
+
+// formatLabelValue returns v if it meets the standards for a Kubernetes
+// label value. Otherwise, it returns a hash which meets the requirements.
+// ref: https://github.com/kubernetes-sigs/cluster-api/blob/010af7f92f98ead971742d347d258a8786d5d57c/util/labels/format/helpers.go
+func formatLabelValue(v string) (string, error) {
+	// a valid Kubernetes label value must:
+	// - be less than 64 characters long.
+	// - be an empty string OR consist of alphanumeric characters, '-', '_' or '.'.
+	// - start and end with an alphanumeric character
+	if len(validation.IsValidLabelValue(v)) == 0 {
+		return v, nil
+	}
+
+	hasher := fnv.New32a()
+	if _, err := hasher.Write([]byte(v)); err != nil {
+		return "", err
+	}
+
+	// use base64 URL encoding to avoid special characters like '/' in the generated
+	// hash
+	return fmt.Sprintf("hash_%s_z",
+		base64.RawURLEncoding.EncodeToString(hasher.Sum(nil))), nil
+}

harvester/labels_test.go

@@ -0,0 +1,38 @@
+package harvester
+
+import "testing"
+
+func TestFormatLabelValue(t *testing.T) {
+	testCases := []struct {
+		desc       string
+		labelValue string
+		expected   string
+	}{
+		{
+			desc:       "return empty string if label value is empty",
+			labelValue: "",
+			expected:   "",
+		},
+		{
+			desc:       "return label value unchanged if it's less than 63 characters",
+			labelValue: "machineSetName",
+			expected:   "machineSetName",
+		},
+		{
+			desc:       "return hashed label value if more than 63 characters",
+			labelValue: "machineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetNamemachineSetName",
+			expected:   "hash_FR_ghQ_z",
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.desc, func(*testing.T) {
+			actual, err := formatLabelValue(tc.labelValue)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if tc.expected != actual {
+				t.Errorf("test case failed: %s. expected %s, got %s", tc.desc, tc.expected, actual)
+			}
+		})
+	}
+}