ObjectManager, providing resource.objects(), is not thread-safe

[miracle2k]

The code in question is here:

pykube/pykube/objects.py

Lines 14 to 23 in e8a4629

	class ObjectManager(object):
	def __call__(self, api, namespace=None):
	if namespace is None and NamespacedAPIObject in getmro(self.api_obj_class):
	namespace = api.config.namespace
	return Query(api, self.api_obj_class, namespace=namespace)
	def __get__(self, obj, api_obj_class):
	assert obj is None, "cannot invoke objects on resource object."
	self.api_obj_class = api_obj_class
	return self

The problem is that the code is expecting __get__ and __call__ to be executed in order. In https://github.com/miracle2k/k8s-snapshots we inadvertently ended up with a situation where that is not the case. Because we are watching two resources, in two separate threads, what happens during setup is that the methods are called in this order:

• ObjectManager.get (for the PersistentVolume resource)
• ObjectManager.get (for the PersistentVolumeClaim resource)
• ObjectManager.call (for the PersistentVolume resource, but with self.api_obj_class set to PersistentVolumeClaim!)
• ObjectManager.call (for the PersistentVolumeClaim resource)

In case it helps, a minimal example to reproduce this (Python 3.6) is here:

https://github.com/miracle2k/k8s-snapshots/tree/pykube-bug