k8s: generate node name if not provided

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

driver/kubernetes/util/generate.go

@@ -0,0 +1,47 @@
+package util
+
+import (
+	"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) {
+	randomName := func() (string, error) {
+		u, err := uuid.NewRandom()
+		if err != nil {
+			return "", err
+		}
+		return names.SimpleNameGenerator.GenerateName(fmt.Sprintf("buildkit-%s-", u)), nil
+	}
+
+	ng, err := txn.NodeGroupByName(builderName)
+	if err != nil {
+		return randomName()
+	}
+
+	var name string
+	for i := 0; i < 6; i++ {
+		name, err = randomName()
+		if err != nil {
+			return "", err
+		}
+		exists := func(name string) bool {
+			for _, n := range ng.Nodes {
+				if n.Name == name {
+					return true
+				}
+			}
+			return false
+		}(name)
+		if exists {
+			continue
+		}
+		return name, nil
+	}
+
+	return "", errors.Errorf("failed to generate random node name")
+}