Post event message for volume attachment

This PR is to add event message when attaching volume fails to help
users to debug. For detach failure, may address in a different PR since
it requires more data structure change.

pkg/controller/volume/attachdetach/cache/desired_state_of_world.go

@@ -322,15 +322,26 @@ func (dsw *desiredStateOfWorld) GetVolumesToAttach() []VolumeToAttach {
 			volumesToAttach = append(volumesToAttach,
 				VolumeToAttach{
 					VolumeToAttach: operationexecutor.VolumeToAttach{
-						VolumeName: volumeName,
+						VolumeName:    volumeName,
-						VolumeSpec: volumeObj.spec,
+						VolumeSpec:    volumeObj.spec,
-						NodeName:   nodeName}})
+						NodeName:      nodeName,
+						ScheduledPods: getPodsFromMap(volumeObj.scheduledPods),
+					}})
 		}
 	}
 
 	return volumesToAttach
 }
 
+// Construct a list of api.Pod objects from the given pod map
+func getPodsFromMap(podMap map[types.UniquePodName]pod) []*api.Pod {
+	pods := make([]*api.Pod, 0, len(podMap))
+	for _, pod := range podMap {
+		pods = append(pods, pod.podObj)
+	}
+	return pods
+}
+
 func (dsw *desiredStateOfWorld) GetPodToAdd() map[types.UniquePodName]PodToAdd {
 	dsw.RLock()
 	defer dsw.RUnlock()

pkg/volume/util/operationexecutor/operation_executor.go

@@ -168,6 +168,12 @@ type VolumeToAttach struct {
 	// NodeName is the identifier for the node that the volume should be
 	// attached to.
 	NodeName string
+
+	// scheduledPods is a map containing the set of pods that reference this
+	// volume and are scheduled to the underlying node. The key in the map is
+	// the name of the pod and the value is a pod object containing more
+	// information about the pod.
+	ScheduledPods []*api.Pod
 }
 
 // VolumeToMount represents a volume that should be attached to this node and
@@ -483,12 +489,15 @@ func (oe *operationExecutor) generateAttachVolumeFunc(
 
 		if attachErr != nil {
 			// On failure, return error. Caller will log and retry.
-			return fmt.Errorf(
+			err := fmt.Errorf(
-				"AttachVolume.Attach failed for volume %q (spec.Name: %q) from node %q with: %v",
+				"Failed to attach volume %q on node %q with: %v",
-				volumeToAttach.VolumeName,
 				volumeToAttach.VolumeSpec.Name(),
 				volumeToAttach.NodeName,
 				attachErr)
+			for _, pod := range volumeToAttach.ScheduledPods {
+				oe.recorder.Eventf(pod, api.EventTypeWarning, kevents.FailedMountVolume, err.Error())
+			}
+			return err
 		}
 
 		glog.Infof(