Authors: Matthew Doherty, Philipp Kuntz, Robert Gogolok

When extending the Kubernetes API with CustomResourceDefinitions you’ll come across the dilemma to clean up external resources when deleting a custom resource. Although you can create a custom resource simply to store and retrieve structured data, most of the time there is some entity involved, like custom controllers. The controller will manage this resource and create other external resources to handle the semantics of that resource. Those external resources should not live forever once the custom resource does not exist anymore. 

In the following text, we’ll work with a custom resource example that represents a data service instance.