webhook

README

Introduction

This mutating webhook modifies a POD spec using specific runtimeclass to remove all resources entries and replace it with peer-pod extended resource.

Need for mutating webhook

A peer-pod uses resources at two places:

• Kubernetes Worker Node: Peer-Pod metadata, Kata shim resources, remote-hypervisor/cloud-api-adaptor resources, vxlan etc
• Cloud Instance: The actual peer-pod VM running in the cloud (eg. EC2 instance in AWS, or Azure VM instance)

For peer-pods case the resources are really consumed outside of the worker node. It’s external to the Kubernetes cluster.

This creates two problems:

1. Peer-pod scheduling can fail due to the unavailability of required resources on the worker node even though the peer-pod will not consume the requested resources from the worker node.

2. Cluster-admin have no way to view the actual peer-pods VM capacity and consumption.

A simple solution to the above problems is to advertise peer-pod capacity as Kubernetes extended resources and let Kubernetes scheduler handle the peer-pod capacity tracking and accounting. Additionally, POD overhead can be used to account for actual cpu and mem resource requirements on the Kubernetes worker node. The mutating webhook removes any resources entries from the Pod spec and adds the peer-pods extended resources.

Installation

Please refer to the following instructions

Development

Please refer to the following instructions