Policies are a critical foundation to successfully build and operate Kubernetes based applications. Rather than making assumptions on how workloads and applications components should work, we can define policies that will govern and enforce the way those workloads and applications components must work.
What Is an Admission Controller?
Kubernetes admission controllers are a powerful native feature, that help define and customize the API resource configurations that can be admitted to a cluster. Described simply, an admission controller is a piece of code that acts on requests made to the Kubernetes API server. They’re invoked prior to the persistence of the object(s) defined by API requests, but after the requests have been authenticated and authorized by the API server.