Merge pull request #50578 from pwittrock/depsutils

Automatic merge from submit-queue (batch tested with PRs 51047, 48573, 50764, 51092, 50578)

Library updates to better support removing kubectl deps on kubernetes/kubernetes

**What this PR does / why we need it**:

**Which issue this PR fixes**: kubernetes/kubectl#50

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

pkg/kubectl/cmd/util/BUILD

@@ -67,6 +67,7 @@ go_library(
         "//vendor/k8s.io/apiserver/pkg/util/flag:go_default_library",
         "//vendor/k8s.io/client-go/discovery:go_default_library",
         "//vendor/k8s.io/client-go/dynamic:go_default_library",
+        "//vendor/k8s.io/client-go/kubernetes:go_default_library",
         "//vendor/k8s.io/client-go/rest:go_default_library",
         "//vendor/k8s.io/client-go/tools/clientcmd:go_default_library",
         "//vendor/k8s.io/client-go/util/homedir:go_default_library",

pkg/kubectl/cmd/util/clientcache.go

@@ -21,6 +21,7 @@ import (
 
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/kubernetes"
 	restclient "k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 	fedclientset "k8s.io/kubernetes/federation/client/clientset_generated/federation_clientset"
@@ -58,6 +59,35 @@ type ClientCache struct {
 	// argument evaluation
 	discoveryClientFactory DiscoveryClientFactory
 	discoveryClient        discovery.DiscoveryInterface
+
+	kubernetesClientCache kubernetesClientCache
+}
+
+// kubernetesClientCache creates a new kubernetes.Clientset one time
+// and then returns the result for all future requests
+type kubernetesClientCache struct {
+	// once makes sure the client is only initialized once
+	once sync.Once
+	// client is the cached client value
+	client *kubernetes.Clientset
+	// err is the cached error value
+	err error
+}
+
+// KubernetesClientSetForVersion returns a new kubernetes.Clientset.  It will cache the value
+// the first time it is called and return the cached value on subsequent calls.
+// If an error is encountered the first time KubernetesClientSetForVersion is called,
+// the error will be cached.
+func (c *ClientCache) KubernetesClientSetForVersion(requiredVersion *schema.GroupVersion) (*kubernetes.Clientset, error) {
+	c.kubernetesClientCache.once.Do(func() {
+		config, err := c.ClientConfigForVersion(requiredVersion)
+		if err != nil {
+			c.kubernetesClientCache.err = err
+			return
+		}
+		c.kubernetesClientCache.client, c.kubernetesClientCache.err = kubernetes.NewForConfig(config)
+	})
+	return c.kubernetesClientCache.client, c.kubernetesClientCache.err
 }
 
 // also looks up the discovery client.  We can't do this during init because the flags won't have been set

pkg/kubectl/cmd/util/factory.go

@@ -43,6 +43,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/serializer/json"
 	"k8s.io/apimachinery/pkg/watch"
 	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/kubernetes"
 	restclient "k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 	fedclientset "k8s.io/kubernetes/federation/client/clientset_generated/federation_clientset"
@@ -91,6 +92,10 @@ type ClientAccessFactory interface {
 
 	// ClientSet gives you back an internal, generated clientset
 	ClientSet() (internalclientset.Interface, error)
+
+	// KubernetesClientSet gives you back an external clientset
+	KubernetesClientSet() (*kubernetes.Clientset, error)
+
 	// Returns a RESTClient for accessing Kubernetes resources or an error.
 	RESTClient() (*restclient.RESTClient, error)
 	// Returns a client.Config for accessing the Kubernetes server.

pkg/kubectl/cmd/util/factory_client_access.go

@@ -37,6 +37,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	utilflag "k8s.io/apiserver/pkg/util/flag"
 	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/kubernetes"
 	restclient "k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 	"k8s.io/client-go/util/homedir"
@@ -167,6 +168,10 @@ func (f *ring0Factory) DiscoveryClient() (discovery.CachedDiscoveryInterface, er
 	return f.discoveryFactory.DiscoveryClient()
 }
 
+func (f *ring0Factory) KubernetesClientSet() (*kubernetes.Clientset, error) {
+	return f.clientCache.KubernetesClientSetForVersion(nil)
+}
+
 func (f *ring0Factory) ClientSet() (internalclientset.Interface, error) {
 	return f.clientCache.ClientSetForVersion(nil)
 }