Kube-proxy learns to read a kubeconfig

--master flag is still supported for distros that need it.
But now, --kubeconfig flag can be used instead, or in addition,
to specify the auth info, and/or the location of the master.

A subsequent PR will change salt to generate a kubeconfig,
and to make kube-proxy use it, for salt-based clouds.

cmd/kube-proxy/app/server.go

@@ -22,11 +22,13 @@ import (
 	"net"
 	"net/http"
 	_ "net/http/pprof"
+	"os"
 	"strconv"
 	"time"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client/clientcmd"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/proxy"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
@@ -40,11 +42,12 @@ import (
 // ProxyServer contains configures and runs a Kubernetes proxy server
 type ProxyServer struct {
 	BindAddress        util.IP
-	ClientConfig       client.Config
 	HealthzPort        int
 	HealthzBindAddress util.IP
 	OOMScoreAdj        int
 	ResourceContainer  string
+	Host               string
+	Kubeconfig         string
 }
 
 // NewProxyServer creates a new ProxyServer object with default parameters
@@ -61,11 +64,12 @@ func NewProxyServer() *ProxyServer {
 // AddFlags adds flags for a specific ProxyServer to the specified FlagSet
 func (s *ProxyServer) AddFlags(fs *pflag.FlagSet) {
 	fs.Var(&s.BindAddress, "bind_address", "The IP address for the proxy server to serve on (set to 0.0.0.0 for all interfaces)")
-	client.BindClientConfigFlags(fs, &s.ClientConfig)
+	fs.StringVar(&s.Host, "master", s.Host, "The address of the Kubernetes API server (overrides any value in kubeconfig)")
 	fs.IntVar(&s.HealthzPort, "healthz_port", s.HealthzPort, "The port to bind the health check server. Use 0 to disable.")
 	fs.Var(&s.HealthzBindAddress, "healthz_bind_address", "The IP address for the health check server to serve on, defaulting to 127.0.0.1 (set to 0.0.0.0 for all interfaces)")
 	fs.IntVar(&s.OOMScoreAdj, "oom_score_adj", s.OOMScoreAdj, "The oom_score_adj value for kube-proxy process. Values must be within the range [-1000, 1000]")
 	fs.StringVar(&s.ResourceContainer, "resource_container", s.ResourceContainer, "Absolute name of the resource-only container to create and run the Kube-proxy in (Default: /kube-proxy).")
+	fs.StringVar(&s.Kubeconfig, "kubeconfig", s.Kubeconfig, "Path to kubeconfig file with authorization and master location information.")
 }
 
 // Run runs the specified ProxyServer.  This should never exit.
@@ -105,9 +109,25 @@ func (s *ProxyServer) Run(_ []string) error {
 	// are registered yet.
 
 	// define api config source
-	if s.ClientConfig.Host != "" {
+	if s.Host != "" || s.Kubeconfig != "" {
-		glog.Infof("Using API calls to get config %v", s.ClientConfig.Host)
+		var kubeconfig *client.Config
-		client, err := client.New(&s.ClientConfig)
+		if s.Kubeconfig != "" {
+			var err error
+			loader := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
+				&clientcmd.ClientConfigLoadingRules{ExplicitPath: s.Kubeconfig},
+				&clientcmd.ConfigOverrides{})
+			kubeconfig, err = loader.ClientConfig()
+			if os.IsNotExist(err) {
+				glog.Fatalf("Could not find kubeconfig file at %s", s.Kubeconfig)
+			}
+			if err != nil {
+				glog.Fatalf("Error loading kubeconfig file \"%s\": %v", s.Kubeconfig, err)
+			}
+		}
+		if s.Host != "" {
+			kubeconfig.Host = s.Host
+		}
+		client, err := client.New(kubeconfig)
 		if err != nil {
 			glog.Fatalf("Invalid API configuration: %v", err)
 		}