Set timeout for accessing credential provider's URL

This changes sets the timeout and also adds the retry mechanism.

pkg/credentialprovider/config.go

@@ -26,8 +26,10 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/golang/glog"
+	"k8s.io/kubernetes/pkg/util/wait"
 )
 
 // DockerConfigJson represents ~/.docker/config.json file info
@@ -48,6 +50,10 @@ type DockerConfigEntry struct {
 	Email    string
 }
 
+const (
+	readURLTimeout = time.Second * 20
+)
+
 var (
 	preferredPathLock sync.Mutex
 	preferredPath     = ""
@@ -138,6 +144,19 @@ func (he *HttpError) Error() string {
 }
 
 func ReadUrl(url string, client *http.Client, header *http.Header) (body []byte, err error) {
+	retryInterval := time.Second
+	wait.PollImmediate(retryInterval, readURLTimeout, func() (bool, error) {
+		body, err = readUrl(url, client, header)
+		if err != nil {
+			glog.V(4).Infof("Error reading %q: %v", url, err)
+			return false, nil
+		}
+		return true, nil
+	})
+	return body, err
+}
+
+func readUrl(url string, client *http.Client, header *http.Header) (body []byte, err error) {
 	req, err := http.NewRequest("GET", url, nil)
 	if err != nil {
 		return nil, err