Move cluster client creation to client.NewInCluster()

Built & pushed nettest:1.4.

contrib/for-tests/network-tester/webserver.go

@@ -37,7 +37,6 @@ import (
 	"io/ioutil"
 	"log"
 	"math/rand"
-	"net"
 	"net/http"
 	"os"
 	"sync"
@@ -202,20 +201,11 @@ func main() {
 // Find all sibling pods in the service and post to their /write handler.
 func contactOthers(state *State) {
 	defer state.doneContactingPeers()
-	token, err := ioutil.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/token")
+	client, err := client.NewInCluster()
 	if err != nil {
-		log.Fatalf("Unable to read service account token: %v", err)
+		log.Fatalf("Unable to create client; error: %v\n", err)
-	}
-	cc := client.Config{
-		Host:        "https://" + net.JoinHostPort(os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT")),
-		Version:     "v1beta3",
-		BearerToken: string(token),
-		Insecure:    true, // TOOD: package certs along with the token
-	}
-	client, err := client.New(&cc)
-	if err != nil {
-		log.Fatalf("Unable to create client:\nconfig: %#v\nerror: %v\n", err)
 	}
+	// Double check that that worked by getting the server version.
 	if v, err := client.ServerVersion(); err != nil {
 		log.Fatalf("Unable to get server version: %v\n", err)
 	} else {

pkg/client/helper.go

@@ -18,6 +18,7 @@ package client
 
 import (
 	"fmt"
+	"io/ioutil"
 	"net"
 	"net/http"
 	"net/url"
@@ -166,6 +167,34 @@ func NewOrDie(c *Config) *Client {
 	return client
 }
 
+// InClusterConfig returns a config object which uses the service account
+// kubernetes gives to pods. It's intended for clients that expect to be
+// running inside a pod running on kuberenetes. It will return an error if
+// called from a process not running in a kubernetes environment.
+func InClusterConfig() (*Config, error) {
+	token, err := ioutil.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/token")
+	if err != nil {
+		return nil, err
+	}
+	return &Config{
+		// TODO: switch to using cluster DNS.
+		Host:        "https://" + net.JoinHostPort(os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT")),
+		Version:     "v1beta3",
+		BearerToken: string(token),
+		// TODO: package certs along with the token
+		Insecure: true,
+	}, nil
+}
+
+// NewInCluster is a shortcut for calling InClusterConfig() and then New().
+func NewInCluster() (*Client, error) {
+	cc, err := InClusterConfig()
+	if err != nil {
+		return nil, err
+	}
+	return New(cc)
+}
+
 // SetKubernetesDefaults sets default values on the provided client config for accessing the
 // Kubernetes API or returns an error if any of the defaults are impossible or invalid.
 func SetKubernetesDefaults(config *Config) error {