There seem to be several issues to go from 1.2 to 1.3 that makes it impossible to upgrade in place.

Is this correct?

When upgrading one worker node to 1.3.4, while the rest is running 1.2.2, the node is never ready

I get lots of 415 errors (unsupported media type?) from kubelet, which seems to indicate incompatible format.

kubelet[2927]: E0804 01:55:13.794921 2927 event.go:198] Server rejected event '&api.Event{TypeMeta:unversioned.TypeMeta{Kind:"", APIVersion:""}, ObjectMeta:api.ObjectMeta{Name:".146777d057f9b62b", GenerateName:"", Namespace:"default", SelfLink:"", UID:"", ResourceVersion:"", Generation:0, CreationTimestamp:unversioned.Time{Time:time.Time{sec:0, nsec:0, loc:(*time.Location)(nil)}}, DeletionTimestamp:(*unversioned.Time)(nil), DeletionGracePeriodSeconds:(*int64)(nil), Labels:map[string]string(nil), Annotations:map[string]string(nil), OwnerReferences:[]api.OwnerReference(nil), Finalizers:[]string(nil)}, InvolvedObject:api.ObjectReference{Kind:"Node", Namespace:"", Name:"198.245.63.87", UID:"xxxxxxxx", APIVersion:"", ResourceVersion:"", FieldPath:""}, Reason:"NodeHasSufficientDisk", Message:"Node xxxxxxxx status is now: NodeHasSufficientDisk", Source:api.EventSource{Component:"kubelet", Host:"xxxxxxxxxx"}, FirstTimestamp:unversioned.Time{Time:time.Time{sec:63605872340, nsec:72642091, loc:(*time.Location)(0x45be3e0)}}, LastTimestamp:unversioned.Time{Time:time.Time{sec:63605872513, nsec:790683013, loc:(*time.Location)(0x45be3e0)}}, Count:29, Type:"Normal"}': 'the server responded with the status code 415 but did not return more information (post events)' (will not retry!)

I'd like to understand if it's a setup issue or a real breaking change that prevent in-place upgrade...

Thanks