driver/kubernetes/util: remove k8s.io/apiserver dependency

Use a simplified local implementation that follow the same semantics,
so that we don't need k8s.io/apiserver as dependency.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

driver/kubernetes/util/generate.go

@@ -1,12 +1,13 @@
 package util
 
 import (
+	"crypto/rand"
+	"encoding/hex"
 	"fmt"
 
 	"github.com/docker/buildx/store"
 	"github.com/google/uuid"
 	"github.com/pkg/errors"
-	"k8s.io/apiserver/pkg/storage/names"
 )
 
 func GenerateNodeName(builderName string, txn *store.Txn) (string, error) {
@@ -15,7 +16,7 @@ func GenerateNodeName(builderName string, txn *store.Txn) (string, error) {
 		if err != nil {
 			return "", err
 		}
-		return names.SimpleNameGenerator.GenerateName(fmt.Sprintf("buildkit-%s-", u)), nil
+		return generateName(fmt.Sprintf("buildkit-%s-", u)), nil
 	}
 
 	ng, err := txn.NodeGroupByName(builderName)
@@ -45,3 +46,30 @@ func GenerateNodeName(builderName string, txn *store.Txn) (string, error) {
 
 	return "", errors.Errorf("failed to generate random node name")
 }
+
+const (
+	maxNameLength          = 63
+	randomLength           = 5
+	maxGeneratedNameLength = maxNameLength - randomLength
+)
+
+// generateName generates the name plus a random suffix of five alphanumerics
+// when a name is requested. The string is guaranteed to not exceed the length
+// of a standard Kubernetes name (63 characters).
+//
+// It's a simplified implementation of k8s.io/apiserver/pkg/storage/names:
+// https://github.com/kubernetes/apiserver/blob/v0.29.2/pkg/storage/names/generate.go#L34-L54
+func generateName(base string) string {
+	if len(base) > maxGeneratedNameLength {
+		base = base[:maxGeneratedNameLength]
+	}
+	return base + randomSuffix()
+}
+
+func randomSuffix() string {
+	b := make([]byte, 32)
+	if _, err := rand.Read(b); err != nil {
+		panic(err) // This shouldn't happen
+	}
+	return hex.EncodeToString(b)[:randomLength]
+}