new driver: kubernetes

Tested with `kind` and GKE.

Note: "nodes" shown in `docker buildx ls` are unrelated to Kubernetes "nodes".
Probably buildx should come up with an alternative term.

Usage:

  $ kind create cluster
  $ export KUBECONFIG="$(kind get kubeconfig-path --name="kind")"

  $ docker buildx create --driver kubernetes --driver-opt replicas=3 --use
  $ docker buildx build -t foo --load .

`--load` loads the image into the local Docker.

Driver opts:

  - `image=IMAGE` - Sets the container image to be used for running buildkit.
  - `namespace=NS` - Sets the Kubernetes namespace. Defaults to the current namespace.
  - `replicas=N` - Sets the number of `Pod` replicas. Defaults to 1.
  - `rootless=(true|false)` - Run the container as a non-root user without `securityContext.privileged`. Defaults to false.
  - `loadbalance=(sticky|random)` - Load-balancing strategy. If set to "sticky", the pod is chosen using the hash of the context path. Defaults to "sticky"

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

vendor/k8s.io/client-go/tools/reference/ref.go

@@ -0,0 +1,126 @@
+/*
+Copyright 2014 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package reference
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"strings"
+
+	"k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/meta"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+var (
+	// Errors that could be returned by GetReference.
+	ErrNilObject  = errors.New("can't reference a nil object")
+	ErrNoSelfLink = errors.New("selfLink was empty, can't make reference")
+)
+
+// GetReference returns an ObjectReference which refers to the given
+// object, or an error if the object doesn't follow the conventions
+// that would allow this.
+// TODO: should take a meta.Interface see http://issue.k8s.io/7127
+func GetReference(scheme *runtime.Scheme, obj runtime.Object) (*v1.ObjectReference, error) {
+	if obj == nil {
+		return nil, ErrNilObject
+	}
+	if ref, ok := obj.(*v1.ObjectReference); ok {
+		// Don't make a reference to a reference.
+		return ref, nil
+	}
+
+	gvk := obj.GetObjectKind().GroupVersionKind()
+
+	// if the object referenced is actually persisted, we can just get kind from meta
+	// if we are building an object reference to something not yet persisted, we should fallback to scheme
+	kind := gvk.Kind
+	if len(kind) == 0 {
+		// TODO: this is wrong
+		gvks, _, err := scheme.ObjectKinds(obj)
+		if err != nil {
+			return nil, err
+		}
+		kind = gvks[0].Kind
+	}
+
+	// An object that implements only List has enough metadata to build a reference
+	var listMeta metav1.Common
+	objectMeta, err := meta.Accessor(obj)
+	if err != nil {
+		listMeta, err = meta.CommonAccessor(obj)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		listMeta = objectMeta
+	}
+
+	// if the object referenced is actually persisted, we can also get version from meta
+	version := gvk.GroupVersion().String()
+	if len(version) == 0 {
+		selfLink := listMeta.GetSelfLink()
+		if len(selfLink) == 0 {
+			return nil, ErrNoSelfLink
+		}
+		selfLinkUrl, err := url.Parse(selfLink)
+		if err != nil {
+			return nil, err
+		}
+		// example paths: /<prefix>/<version>/*
+		parts := strings.Split(selfLinkUrl.Path, "/")
+		if len(parts) < 4 {
+			return nil, fmt.Errorf("unexpected self link format: '%v'; got version '%v'", selfLink, version)
+		}
+		if parts[1] == "api" {
+			version = parts[2]
+		} else {
+			version = parts[2] + "/" + parts[3]
+		}
+	}
+
+	// only has list metadata
+	if objectMeta == nil {
+		return &v1.ObjectReference{
+			Kind:            kind,
+			APIVersion:      version,
+			ResourceVersion: listMeta.GetResourceVersion(),
+		}, nil
+	}
+
+	return &v1.ObjectReference{
+		Kind:            kind,
+		APIVersion:      version,
+		Name:            objectMeta.GetName(),
+		Namespace:       objectMeta.GetNamespace(),
+		UID:             objectMeta.GetUID(),
+		ResourceVersion: objectMeta.GetResourceVersion(),
+	}, nil
+}
+
+// GetPartialReference is exactly like GetReference, but allows you to set the FieldPath.
+func GetPartialReference(scheme *runtime.Scheme, obj runtime.Object, fieldPath string) (*v1.ObjectReference, error) {
+	ref, err := GetReference(scheme, obj)
+	if err != nil {
+		return nil, err
+	}
+	ref.FieldPath = fieldPath
+	return ref, nil
+}