Move image pull throttling logic to kubelet/images

This allows runtimes in different packages (dockertools, rkt, kuberuntime) to
share the same logic. Before this change, only dockertools support this
feature. Now all three packages support image pull throttling.

pkg/kubelet/images/image_manager.go

@@ -29,27 +29,29 @@ import (
 
 // imageManager provides the functionalities for image pulling.
 type imageManager struct {
-	recorder record.EventRecorder
-	runtime  kubecontainer.Runtime
-	backOff  *flowcontrol.Backoff
+	recorder     record.EventRecorder
+	imageService kubecontainer.ImageService
+	backOff      *flowcontrol.Backoff
 	// It will check the presence of the image, and report the 'image pulling', image pulled' events correspondingly.
 	puller imagePuller
 }
 
 var _ ImageManager = &imageManager{}
 
-func NewImageManager(recorder record.EventRecorder, runtime kubecontainer.Runtime, imageBackOff *flowcontrol.Backoff, serialized bool) ImageManager {
+func NewImageManager(recorder record.EventRecorder, imageService kubecontainer.ImageService, imageBackOff *flowcontrol.Backoff, serialized bool, qps float32, burst int) ImageManager {
+	imageService = throttleImagePulling(imageService, qps, burst)
+
 	var puller imagePuller
 	if serialized {
-		puller = newSerialImagePuller(runtime)
+		puller = newSerialImagePuller(imageService)
 	} else {
-		puller = newParallelImagePuller(runtime)
+		puller = newParallelImagePuller(imageService)
 	}
 	return &imageManager{
-		recorder: recorder,
-		runtime:  runtime,
-		backOff:  imageBackOff,
-		puller:   puller,
+		recorder:     recorder,
+		imageService: imageService,
+		backOff:      imageBackOff,
+		puller:       puller,
 	}
 }
 
@@ -86,7 +88,7 @@ func (m *imageManager) EnsureImageExists(pod *api.Pod, container *api.Container,
 	}
 
 	spec := kubecontainer.ImageSpec{Image: container.Image}
-	present, err := m.runtime.IsImagePresent(spec)
+	present, err := m.imageService.IsImagePresent(spec)
 	if err != nil {
 		msg := fmt.Sprintf("Failed to inspect image %q: %v", container.Image, err)
 		m.logIt(ref, api.EventTypeWarning, events.FailedToInspectImage, logPrefix, msg, glog.Warning)