- For metrics `apiserver_cache_list_fetched_objects_total`, `apiserver_cache_list_returned_objects_total`, `apiserver_cache_list_total` replace `resource_prefix` label with API `group` and `resource` labels.
  For metrics `etcd_request_duration_seconds`, `etcd_requests_total` and `etcd_request_errors_total` replace `type` label with API `resource` and `group` label.
  For metric `apiserver_selfrequest_total` add a API `group` label.

- Removed the following deprecated metrics:
  - node_collector_evictions_number replaced by node_collector_evictions_total
  - scheduler_e2e_scheduling_duration_seconds replaced by scheduler_scheduling_attempt_duration_seconds ([#115209](https://github.com/kubernetes/kubernetes/pull/115209), [@dgrisonnet](https://github.com/dgrisonnet))

### API Change

The `IngressClass` resource is used to describe a type of Ingress within a Kubernetes cluster. Ingresses can specify the class they are associated with by using a new `ingressClassName` field on Ingresses. This new resource and field replace the deprecated `kubernetes.io/ingress.class` annotation.

### SIG CLI introduces kubectl debug

* Make all e2e tests lookup image to use from a centralized place. In that centralized place, add support for multiple platforms. ([#49457](https://github.com/kubernetes/kubernetes/pull/49457), [@mkumatag](https://github.com/mkumatag))

- kube-controller-manager now uses the informer cache instead of active pod gets in HPA controller ([#68241](https://github.com/kubernetes/kubernetes/pull/68241), [@krzysztof-jastrzebski](https://github.com/krzysztof-jastrzebski))

- Fixes a regression in v1beta1 PodDisruptionBudget handling of `strategic merge patch`-type API requests for the `selector` field. Prior to 1.21, these requests would merge `matchLabels` content and replace `matchExpressions` content. In 1.21, patch requests touching the `selector` field started replacing the entire selector. This is consistent with server-side apply and the v1 PodDisruptionBudget behavior, but should not have been changed for v1beta1....

- `cluster/gce`: added webhook to replace `PersistentVolumeLabel` admission controller. ([#121628](https://github.com/kubernetes/kubernetes/pull/121628), [@andrewsykim](https://github.com/andrewsykim))

* Remove DirectCodecFactory(replace with serializer.WithoutConversionCodecFactory), DirectEncoder(replace with runtime.WithVersionEncoder) and DirectDecoder(replace with runtime.WithoutVersionDecoder). action required ([#79263](https://github.com/kubernetes/kubernetes/pull/79263), [@draveness](https://github.com/draveness))

### API Change