PodDisruputionBudget for knative service pods

In what area(s)?

/area autoscale

Describe the feature

Although Knative autoscaling can maintain a number of minimum replicas per revision, I think this is only limited to actions that Knative controls. If other actors evict Knative service pods, then the service may have less available pods than the minimum replicas. One example of other actors that can mess up the Knative minimum state is the high-performance cluster autoscaler Karpenter which has a consolidation feature.

The way I'm trying to mitigate this problem is manually creating a PodDisruptionBudget targeting the pods of my Knative service, with the PDB's minAvailable value set to the KSVC's autoscaling.knative.dev/min-scale value.

I was asked by @dprotaso to mention my case in a Github issue here, so please let me know what you think.

Start with the autoscale area and Kubernetes PodDisruptionBudget behavior described in the issue. Determine how a PDB could track a Knative service's autoscaling.knative.dev/min-scale value without conflicting with Knative-controlled pod lifecycle. Done means the proposed behavior is defined and validated for externally evicted service pods.