use inClusterConfig before using default config for cluster components

cmd/kube-controller-manager/app/controllermanager.go

@@ -35,7 +35,6 @@ import (
 	"k8s.io/kubernetes/pkg/api/unversioned"
 	client "k8s.io/kubernetes/pkg/client/unversioned"
 	"k8s.io/kubernetes/pkg/client/unversioned/clientcmd"
-	clientcmdapi "k8s.io/kubernetes/pkg/client/unversioned/clientcmd/api"
 	"k8s.io/kubernetes/pkg/cloudprovider"
 	"k8s.io/kubernetes/pkg/controller/daemon"
 	"k8s.io/kubernetes/pkg/controller/deployment"
@@ -234,15 +233,7 @@ func (s *CMServer) ResyncPeriod() time.Duration {
 
 // Run runs the CMServer.  This should never exit.
 func (s *CMServer) Run(_ []string) error {
-	if s.Kubeconfig == "" && s.Master == "" {
-		glog.Warningf("Neither --kubeconfig nor --master was specified.  Using default API client.  This might not work.")
-	}
-
-	// This creates a client, first loading any specified kubeconfig
-	// file, and then overriding the Master flag, if non-empty.
-	kubeconfig, err := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
-		&clientcmd.ClientConfigLoadingRules{ExplicitPath: s.Kubeconfig},
-		&clientcmd.ConfigOverrides{ClusterInfo: clientcmdapi.Cluster{Server: s.Master}}).ClientConfig()
+	kubeconfig, err := clientcmd.BuildConfigFromFlags(s.Master, s.Kubeconfig)
 	if err != nil {
 		return err
 	}

pkg/client/unversioned/clientcmd/client_config.go

@@ -22,6 +22,7 @@ import (
 	"net/url"
 	"os"
 
+	"github.com/golang/glog"
 	"github.com/imdario/mergo"
 
 	"k8s.io/kubernetes/pkg/api"
@@ -335,3 +336,23 @@ func (inClusterClientConfig) Possible() bool {
 		os.Getenv("KUBERNETES_SERVICE_PORT") != "" &&
 		err == nil && !fi.IsDir()
 }
+
+// BuildConfigFromFlags is a helper function that builds configs from a master
+// url or a kubeconfig filepath. These are passed in as command line flags for cluster
+// components. Warnings should reflect this usage. If neither masterUrl or kubeconfigPath
+// are passed in we fallback to inClusterConfig. If inClusterConfig fails, we fallback
+// to the default config.
+func BuildConfigFromFlags(masterUrl, kubeconfigPath string) (*client.Config, error) {
+	if kubeconfigPath == "" && masterUrl == "" {
+		glog.Warningf("Neither --kubeconfig nor --master was specified.  Using the inClusterConfig.  This might not work.")
+		kubeconfig, err := client.InClusterConfig()
+		if err == nil {
+			return kubeconfig, nil
+		}
+		glog.Warning("error creating inClusterConfig, falling back to default config: %v", err)
+	}
+
+	return NewNonInteractiveDeferredLoadingClientConfig(
+		&ClientConfigLoadingRules{ExplicitPath: kubeconfigPath},
+		&ConfigOverrides{ClusterInfo: clientcmdapi.Cluster{Server: masterUrl}}).ClientConfig()
+}

plugin/cmd/kube-scheduler/app/server.go

@@ -30,7 +30,6 @@ import (
 	"k8s.io/kubernetes/pkg/client/record"
 	client "k8s.io/kubernetes/pkg/client/unversioned"
 	"k8s.io/kubernetes/pkg/client/unversioned/clientcmd"
-	clientcmdapi "k8s.io/kubernetes/pkg/client/unversioned/clientcmd/api"
 	"k8s.io/kubernetes/pkg/healthz"
 	"k8s.io/kubernetes/pkg/master/ports"
 	"k8s.io/kubernetes/pkg/util"
@@ -112,15 +111,7 @@ func (s *SchedulerServer) AddFlags(fs *pflag.FlagSet) {
 
 // Run runs the specified SchedulerServer.  This should never exit.
 func (s *SchedulerServer) Run(_ []string) error {
-	if s.Kubeconfig == "" && s.Master == "" {
-		glog.Warningf("Neither --kubeconfig nor --master was specified.  Using default API client.  This might not work.")
-	}
-
-	// This creates a client, first loading any specified kubeconfig
-	// file, and then overriding the Master flag, if non-empty.
-	kubeconfig, err := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
-		&clientcmd.ClientConfigLoadingRules{ExplicitPath: s.Kubeconfig},
-		&clientcmd.ConfigOverrides{ClusterInfo: clientcmdapi.Cluster{Server: s.Master}}).ClientConfig()
+	kubeconfig, err := clientcmd.BuildConfigFromFlags(s.Master, s.Kubeconfig)
 	if err != nil {
 		return err
 	}