incorrectly placed a pod in the "unschedulable" queue instead of the "backoff" queue. This happened when some plugin previously declared the pod as "unschedulable" and then in a later attempt encounters some other error. Scheduling of that pod then got delayed by up to five minutes, after which periodic flushing moved the pod back into the "active" queue. ([#120334](https://github.com/kubernetes/kubernetes/pull/120334), [@pohly](https://github.com/pohly)) [SIG Scheduling]

### Other (Cleanup...

- Kubeadm: add a upgrade health check that deploys a Job ([#81319](https://github.com/kubernetes/kubernetes/pull/81319), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]
- Kubeadm: add the experimental feature gate PublicKeysECDSA that can be used to create a

* kubeadm now accepts `--apiserver-extra-args`, `--controller-manager-extra-args` and `--scheduler-extra-args`, making it possible to override / specify additional flags for control plane components. One good example is to deploy Kubernetes with a different admission-control flag on API server. ([#58080](https://github.com/kubernetes/kubernetes/pull/58080), [@simonferquel](https://github.com/simonferquel))

    val response = client.newCall(request).execute()
    val bodySource = response.body.source()
    assertThat(bodySource.readByte()).isEqualTo('d'.code.toByte())

    // The second byte of this request will be delayed by 750ms so we should time out after 250ms.
    val startNanos = System.nanoTime()
    bodySource.use {
      assertFailsWith<IOException> {
        bodySource.readByte()
      }.also { expected ->

- CoreDNS is only officially supported on Linux at this time.  As such, when kubeadm is used to deploy this component into your kubernetes cluster, it will be restricted (using `nodeSelectors`) to run only on nodes with that operating system. This ensures that in clusters which include Windows nodes, the scheduler will not ever attempt to place CoreDNS...

incorrectly placed a pod in the "unschedulable" queue instead of the "backoff" queue. This happened when some plugin previously declared the pod as "unschedulable" and then in a later attempt encounters some other error. Scheduling of that pod then got delayed by up to five minutes, after which periodic flushing moved the pod back into the "active" queue. ([#120334](https://github.com/kubernetes/kubernetes/pull/120334), [@pohly](https://github.com/pohly)) [SIG Scheduling]

### Other (Cleanup...

* Stackdriver cluster logging now deploys a new component to export Kubernetes events. ([#46700](https://github.com/kubernetes/kubernetes/pull/46700), [@crassirostris](https://github.com/crassirostris))

- Introduce `node.kubernetes.io/exclude-balancer` and `node.kubernetes.io/exclude-disruption` labels in alpha to prevent cluster deployers from being dependent on the optional `node-role` labels which not all clusters may provide. ([#80238](https://github.com/kubernetes/kubernetes/pull/80238), [@smarterclayton](https://github.com/smarterclayton))

incorrectly placed a pod in the "unschedulable" queue instead of the "backoff" queue. This happened when some plugin previously declared the pod as "unschedulable" and then in a later attempt encounters some other error. Scheduling of that pod then got delayed by up to five minutes, after which periodic flushing moved the pod back into the "active" queue. ([#120334](https://github.com/kubernetes/kubernetes/pull/120334), [@pohly](https://github.com/pohly)) [SIG Scheduling]

### Other (Cleanup...

features and stability work required for bootstrapping production clusters efficiently. kubeadm has promoted high availability (HA) capability to beta, allowing users to use the familiar `kubeadm init` and `kubeadm join` commands to [configure and deploy an HA control plane](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/high-availability/). An entire new test suite has been created specifically for ensuring these features will stay stable over time.

Certificate...