- The scheduler retries scheduling Pods rejected by PreFilterResult (PreFilter plugins) more appropriately; it now takes events registered in those rejector PreFilter plugins into consideration. ([#122251](https://github.com/kubernetes/kubernetes/pull/122251), [@olderTaoist](https://github.com/olderTaoist)) [SIG Scheduling and Testing]

- Kube-scheduler now retries scheduling Pods rejected by the PodTopologySpread plugin when related Pods are created, deleted, updated,...

  which the scheduler might miss some updates for the Pods rejected by NodeUnschedulable plugin and put the Pods in the queue for a longer time than needed. ([#127427](https://github.com/kubernetes/kubernetes/pull/127427), [@sanposhiho](https://github.com/sanposhiho)) [SIG Scheduling]
- Fixes the bug in PodTopologySpread that only happens with QHint enabled, 

- Kubeadm: add support for dry running `kubeadm...

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.
  Now, the scheduling queue notices extenders' failures and requeue Pods rejected by Extenders appropriately. ([#122022](https://github.com/kubernetes/kubernetes/pull/122022), [@sanposhiho](https://github.com/sanposhiho)) [SIG Scheduling]

* Fix a bug in apiserver that could cause a valid update request to be rejected with a precondition check failure. ([#82303](https://github.com/kubernetes/kubernetes/pull/82303), [@roycaihw](https://github.com/roycaihw))

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.
  Now, the scheduling queue notices extenders' failures and requeue Pods rejected by Extenders appropriately. ([#122044](https://github.com/kubernetes/kubernetes/pull/122044), [@sanposhiho](https://github.com/sanposhiho)) [SIG Scheduling]

- The `rejected` label in `apiserver_admission_webhook_admission_duration_seconds` metrics now properly indicates if the request was rejected. ([#81399](https://github.com/kubernetes/kubernetes/pull/81399), [@roycaihw](https://github.com/roycaihw))

`admissionregistration.k8s.io/v1beta1.MutatingWebhookConfiguration` so that webhooks can explicitly register as having dry-run support. If a dry-run request is made on a resource that triggers a non dry-run supporting webhook, the request will be completely rejected, with "400: Bad Request". Additionally, a new field is being added to the `admission.k8s.io/v1beta1.AdmissionReview` API object, exposing to webhooks whether or not the request being reviewed is a dry-run. ([#66936](https://github.com/kubernetes...

* Metadata of CustomResources is now pruned and schema-checked during deserialization of requests and when read from etcd. In the former case, invalid meta data is rejected, in the later it is dropped from the CustomResource objects. ([#64267](https://github.com/kubernetes/kubernetes/pull/64267), [@sttts](https://github.com/sttts))