add GetConfigWithContext to retrieve a config with a specific context

Author: sbueringer

Gopkg.lock

@@ -25,6 +25,7 @@ import (
 
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
+	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
 	logf "sigs.k8s.io/controller-runtime/pkg/internal/log"
 )
 
@@ -61,7 +62,27 @@ func init() {
 //
 // * $HOME/.kube/config if exists
 func GetConfig() (*rest.Config, error) {
-	cfg, err := loadConfig()
+	return GetConfigWithContext("")
+}
+
+// GetConfigWithContext creates a *rest.Config for talking to a Kubernetes API server with a specific context.
+// If --kubeconfig is set, will use the kubeconfig file at that location.  Otherwise will assume running
+// in cluster and use the cluster provided kubeconfig.
+//
+// It also applies saner defaults for QPS and burst based on the Kubernetes
+// controller manager defaults (20 QPS, 30 burst)
+//
+// Config precedence
+//
+// * --kubeconfig flag pointing at a file
+//
+// * KUBECONFIG environment variable pointing at a file
+//
+// * In-cluster config if running in cluster
+//
+// * $HOME/.kube/config if exists
+func GetConfigWithContext(context string) (*rest.Config, error) {
+	cfg, err := loadConfig(context)
 	if err != nil {
 		return nil, err
 	}
@@ -75,30 +96,42 @@ func GetConfig() (*rest.Config, error) {
 }
 
 // loadConfig loads a REST Config as per the rules specified in GetConfig
-func loadConfig() (*rest.Config, error) {
+func loadConfig(context string) (*rest.Config, error) {
+
 	// If a flag is specified with the config location, use that
 	if len(kubeconfig) > 0 {
-		return clientcmd.BuildConfigFromFlags(apiServerURL, kubeconfig)
+		return loadConfigWithContext(apiServerURL, kubeconfig, context)
 	}
-	// If an env variable is specified with the config locaiton, use that
+	// If an env variable is specified with the config location, use that
 	if len(os.Getenv("KUBECONFIG")) > 0 {
-		return clientcmd.BuildConfigFromFlags(apiServerURL, os.Getenv("KUBECONFIG"))
+		return loadConfigWithContext(apiServerURL, os.Getenv("KUBECONFIG"), context)
 	}
 	// If no explicit location, try the in-cluster config
 	if c, err := rest.InClusterConfig(); err == nil {
 		return c, nil
 	}
 	// If no in-cluster config, try the default location in the user's home directory
 	if usr, err := user.Current(); err == nil {
-		if c, err := clientcmd.BuildConfigFromFlags(
-			"", filepath.Join(usr.HomeDir, ".kube", "config")); err == nil {
+		if c, err := loadConfigWithContext(apiServerURL, filepath.Join(usr.HomeDir, ".kube", "config"),
+			context); err == nil {
 			return c, nil
 		}
 	}
 
 	return nil, fmt.Errorf("could not locate a kubeconfig")
 }
 
+func loadConfigWithContext(apiServerURL, kubeconfig, context string) (*rest.Config, error) {
+	return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
+		&clientcmd.ClientConfigLoadingRules{ExplicitPath: kubeconfig},
+		&clientcmd.ConfigOverrides{
+			ClusterInfo: clientcmdapi.Cluster{
+				Server: apiServerURL,
+			},
+			CurrentContext: context,
+		}).ClientConfig()
+}
+
 // GetConfigOrDie creates a *rest.Config for talking to a Kubernetes apiserver.
 // If --kubeconfig is set, will use the kubeconfig file at that location.  Otherwise will assume running
 // in cluster and use the cluster provided kubeconfig.