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/plugin/pkg/client/auth/openstack/openstack.go

@@ -0,0 +1,193 @@
+/*
+Copyright 2017 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 openstack
+
+import (
+	"fmt"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/golang/glog"
+	"github.com/gophercloud/gophercloud"
+	"github.com/gophercloud/gophercloud/openstack"
+
+	"k8s.io/apimachinery/pkg/util/net"
+	restclient "k8s.io/client-go/rest"
+)
+
+func init() {
+	if err := restclient.RegisterAuthProviderPlugin("openstack", newOpenstackAuthProvider); err != nil {
+		glog.Fatalf("Failed to register openstack auth plugin: %s", err)
+	}
+}
+
+// DefaultTTLDuration is the time before a token gets expired.
+const DefaultTTLDuration = 10 * time.Minute
+
+// openstackAuthProvider is an authprovider for openstack. this provider reads
+// the environment variables to determine the client identity, and generates a
+// token which will be inserted into the request header later.
+type openstackAuthProvider struct {
+	ttl         time.Duration
+	tokenGetter TokenGetter
+}
+
+// TokenGetter returns a bearer token that can be inserted into request.
+type TokenGetter interface {
+	Token() (string, error)
+}
+
+type tokenGetter struct {
+	authOpt *gophercloud.AuthOptions
+}
+
+// Token creates a token by authenticate with keystone.
+func (t *tokenGetter) Token() (string, error) {
+	var options gophercloud.AuthOptions
+	var err error
+	if t.authOpt == nil {
+		// reads the config from the environment
+		glog.V(4).Info("reading openstack config from the environment variables")
+		options, err = openstack.AuthOptionsFromEnv()
+		if err != nil {
+			return "", fmt.Errorf("failed to read openstack env vars: %s", err)
+		}
+	} else {
+		options = *t.authOpt
+	}
+	client, err := openstack.AuthenticatedClient(options)
+	if err != nil {
+		return "", fmt.Errorf("authentication failed: %s", err)
+	}
+	return client.TokenID, nil
+}
+
+// cachedGetter caches a token until it gets expired, after the expiration, it will
+// generate another token and cache it.
+type cachedGetter struct {
+	mutex       sync.Mutex
+	tokenGetter TokenGetter
+
+	token string
+	born  time.Time
+	ttl   time.Duration
+}
+
+// Token returns the current available token, create a new one if expired.
+func (c *cachedGetter) Token() (string, error) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	var err error
+	// no token or exceeds the TTL
+	if c.token == "" || time.Since(c.born) > c.ttl {
+		c.token, err = c.tokenGetter.Token()
+		if err != nil {
+			return "", fmt.Errorf("failed to get token: %s", err)
+		}
+		c.born = time.Now()
+	}
+	return c.token, nil
+}
+
+// tokenRoundTripper implements the RoundTripper interface: adding the bearer token
+// into the request header.
+type tokenRoundTripper struct {
+	http.RoundTripper
+
+	tokenGetter TokenGetter
+}
+
+var _ net.RoundTripperWrapper = &tokenRoundTripper{}
+
+// RoundTrip adds the bearer token into the request.
+func (t *tokenRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	// if the authorization header already present, use it.
+	if req.Header.Get("Authorization") != "" {
+		return t.RoundTripper.RoundTrip(req)
+	}
+
+	token, err := t.tokenGetter.Token()
+	if err == nil {
+		req.Header.Set("Authorization", "Bearer "+token)
+	} else {
+		glog.V(4).Infof("failed to get token: %s", err)
+	}
+
+	return t.RoundTripper.RoundTrip(req)
+}
+
+func (t *tokenRoundTripper) WrappedRoundTripper() http.RoundTripper { return t.RoundTripper }
+
+// newOpenstackAuthProvider creates an auth provider which works with openstack
+// environment.
+func newOpenstackAuthProvider(_ string, config map[string]string, persister restclient.AuthProviderConfigPersister) (restclient.AuthProvider, error) {
+	var ttlDuration time.Duration
+	var err error
+
+	glog.Warningf("WARNING: in-tree openstack auth plugin is now deprecated. please use the \"client-keystone-auth\" kubectl/client-go credential plugin instead")
+	ttl, found := config["ttl"]
+	if !found {
+		ttlDuration = DefaultTTLDuration
+		// persist to config
+		config["ttl"] = ttlDuration.String()
+		if err = persister.Persist(config); err != nil {
+			return nil, fmt.Errorf("failed to persist config: %s", err)
+		}
+	} else {
+		ttlDuration, err = time.ParseDuration(ttl)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse ttl config: %s", err)
+		}
+	}
+
+	authOpt := gophercloud.AuthOptions{
+		IdentityEndpoint: config["identityEndpoint"],
+		Username:         config["username"],
+		Password:         config["password"],
+		DomainName:       config["name"],
+		TenantID:         config["tenantId"],
+		TenantName:       config["tenantName"],
+	}
+
+	getter := tokenGetter{}
+	// not empty
+	if (authOpt != gophercloud.AuthOptions{}) {
+		if len(authOpt.IdentityEndpoint) == 0 {
+			return nil, fmt.Errorf("empty %q in the config for openstack auth provider", "identityEndpoint")
+		}
+		getter.authOpt = &authOpt
+	}
+
+	return &openstackAuthProvider{
+		ttl:         ttlDuration,
+		tokenGetter: &getter,
+	}, nil
+}
+
+func (oap *openstackAuthProvider) WrapTransport(rt http.RoundTripper) http.RoundTripper {
+	return &tokenRoundTripper{
+		RoundTripper: rt,
+		tokenGetter: &cachedGetter{
+			tokenGetter: oap.tokenGetter,
+			ttl:         oap.ttl,
+		},
+	}
+}
+
+func (oap *openstackAuthProvider) Login() error { return nil }