The new handler is meant to be executed at the end of the delegation chain.
It simply checks if the request have been made before the server has installed all known HTTP paths.
In that case it returns a 503 response otherwise it returns a 404.
We don't want to add additional checks to the readyz path as it might prevent fixing bricked clusters.
This specific handler is meant to "protect" requests that arrive before the paths and handlers are fully initialized.
Kubernetes-commit: 53867975e72c7a2d2dd94aac6bd2869411f92094
Lukasz Szaszkiewicz