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Summary

This webhook is used to validate licensing requirements on ROSA to ensure that windows virtual machines do not exceed the total capacity of the windows nodes provided.

WARN this was created as a proof-of-concept only. Please use at your own risk.

Limitations

There are several known limitations to the webhook:

  1. Only accounts for CREATE requests and not UPDATE requests
  2. Logic between domain.cpu and requests/limits has not yet been determined (see #1)
  3. For simplicity, only VirtualMachineInstance types are validated
    • VirtualMachine objects may also be validated but the logic was beyond a simple proof-of-concept. The result of this means that users who submit a VirtualMachine to the API will be successful, but the subordinate VirutalMachineInstance object will fail creation, much like the relationship between Deployments and ReplicaSets and Pods.
    • There may also be more objects to be validated beyond VirtualMachine and VirtualMachineInstance objects.
  4. Depends on node labels via WEBHOOK_NODE_LABEL_KEY and WEBHOOK_NODE_LABEL_VALUES input. If nodes are missing labels, they will not be used to calculate the total capacity for windows nodes in the cluster. This is defaulted in the standard installation process in this README.
  5. Validation happens prior to scheduling.
  6. Test manifests exist in the manifests/test directory.

WARN be advised that the test manifests contain passwords in cleartext for testing only. This in not intended to be for production use and was simply used to validate the proof-of-concept.

Usage

This is simple usage for the webhook. Please review the manifests/deploy.yaml file for accuracy for your environment. You will need to clone this repository and change to the cloned repository directory to run through these instructions.

  1. Webhooks need their own set of certificates in order to properly function. You can create your own with a simple script provided in this repository:
make certs

If you do not use the script, be sure to create the following files:

  • CA Certificate - tmp/ca.crt - The CA certificate used to sign the webhook web certificate.
  • Webhook Key - tmp/server.key - The webhook server key.
  • Webhook Cert - tmp/server.crt - The webhook server certificate, signed by the tmp/ca.crt file (above). It should be noted that the certificate must be requested with windows-overcommit-webhook.windows-overcommit-webhook.svc as the common name and/or subject alternative name, as this is the name the Kubernetes API expects. Please see the scripts/gen-certs.sh for an example.
  1. Create the webhook in the ROSA cluster. This step assumes you have a functioning ROSA cluster and your KUBECONFIG configured to run commands against the cluster:
make create
  1. Once you have installed OpenShift Virtualization (see https://cloud.redhat.com/experts/rosa/ocp-virt/with-fsx/ for a quick start) your requests for VirtualMachine and VirtualMachineInstances will be successfully validated by the webhook.

Cleanup

  1. To cleanup the webhook configuration, and the deployment, namespace and certificates, simply run:
make destroy