Epic Goal

• Allow users to choose the "priority" and "least-waste" expanders when creating a ClusterAutoscaler resource.

Why is this important?

• The priority expander gives users the capability to instruct the cluster autoscaler about preferred node groups that it should expand. In this manner, a user can dictate to the cluster autoscaler which MachineSets should take priority when scaling up the cluster.
• The least-waste expander gives users the capability to instruct the cluster autoscaler to choose instance sizes which will have the least amount of cpu and memory resource wastage when choosing for pending pods. It is a great supplement the priority expander to give backup option when multiple instance sizes might work.

Scenarios

1. As a user I would like the cluster autoscaler to prefer MachineSets that use spot instances as it will lower my costs. By using the priority expander, I can indicate to the cluster autoscaler which MachineSets should be utilized first when scaling up the cluster.
2. As a user I wan the autoscaler to prefer instance sizes which produce the least amount of wasted cpu and memory resources. By using the least-waste expander I can instruct the autoscaler to make this decision.

Acceptance Criteria

• CI - MUST be running successfully with tests automated
• Release Technical Enablement - Provide necessary release enablement details and documents.
• New e2e tests added to exercise this functionality

Dependencies (internal and external)

1. ...

Previous Work (Optional):

1. …

Open questions::

1. Is there any automation we want to add to the CAO to make this easier for users? (eg a new field on MachineAutoscaler to indicate a priority)

Done Checklist

• CI - CI is running, tests are automated and merged.
• Release Enablement <link to Feature Enablement Presentation>
• DEV - Upstream code and tests merged: <link to meaningful PR or GitHub Issue>
• DEV - Upstream documentation merged: <link to meaningful PR or GitHub Issue>
• DEV - Downstream build attached to advisory: <link to errata>
• QE - Test plans in Polarion: <link or reference to Polarion>
• QE - Automated tests merged: <link or reference to automated tests>
• DOC - Downstream documentation merged: <link to meaningful PR>