* Kubelet won't evict a static pod with priority `system-node-critical` upon resource pressure. ([#74222](https://github.com/kubernetes/kubernetes/pull/74222), [@Huang-Wei](https://github.com/Huang-Wei))

- Some apiserver metrics were changed, as follows.
  - `priority_level_seat_count_samples` is replaced with `priority_level_seat_utilization`, which samples every nanosecond rather than every millisecond; the old metric conveyed utilization despite its name.
  - `priority_level_seat_count_watermarks` is removed.

  
  action required

- This PR adds the following metrics for API Priority and Fairness.
  - **apiserver_flowcontrol_priority_level_seat_count_samples**: histograms of seats occupied by executing requests (both regular and final-delay phases included), broken down by priority_level; the observations are taken once per millisecond.

### API Priority and Fairness graduates to Beta

Initially introduced in 1.18, Kubernetes 1.20 now enables API Priority and Fairness (APF) by default. This allows `kube-apiserver` to [categorize incoming requests by priority levels](https://docs.k8s.io/concepts/cluster-administration/flow-control/).

### IPv4/IPv6 run

- 'Priority and Fairness has introduced a new feature called _borrowing_ that allows an API priority level
  to borrow a number of seats from other priority level(s). As a cluster operator, you can enable borrowing
  for a certain priority level configuration object via the two newly introduced fields `lendablePercent`, and

- Update default API priority-and-fairness config to avoid endpoint/configmaps operations from controller-manager to all match leader-election priority level. ([#106725](https://github.com/kubernetes/kubernetes/pull/106725), [@wojtek-t](https://github.com/wojtek-t)) [SIG API Machinery]

### Feature

- A new Priority and Fairness metric 'apiserver_flowcontrol_work_estimate_seats_samples' has been 

## Changelog since v1.19.10

## Changes by Kind

### API Change

- We have added a new Priority & Fairness rule that exempts all probes (/readyz, /healthz, /livez) to prevent 

- Restores priority of static control plane pods in the cluster/gce/manifests control-plane manifests ([#89970](https://github.com/kubernetes/kubernetes/pull/89970), [@liggitt](https://github.com/liggitt)) [SIG Cluster Lifecycle and Node]

Pod Priority and Preemption in Kubernetes ([#564](https://github.com/kubernetes/enhancements/issues/564))

- Pod priority and preemption enables Kubernetes scheduler to schedule more important Pods first and when cluster is out of resources, it removes less important pods to create room for more important ones. The importance is specified by priority.