* Fix a potential bug that scheduler preempts unnecessary pods. ([#70898](https://github.com/kubernetes/kubernetes/pull/70898), [@Huang-Wei](https://github.com/Huang-Wei))
* The kube-apiserver's healthz now takes in an optional query parameter which allows you to disable health checks from causing healthz failures.  ([#70676](https://github.com/kubernetes/kubernetes/pull/70676), [@logicalhan](https://github.com/logicalhan))

- Mark Job onPodConditions as optional in pod failure policy ([#120208](https://github.com/kubernetes/kubernetes/pull/120208), [@mimowo](https://github.com/mimowo)) [SIG API Machinery and Apps]

### Feature

- Added optional `--detect-local-mode` flag to kube-proxy. Valid values are "ClusterCIDR" (default matching previous behavior) and "NodeCIDR" ([#87748](https://github.com/kubernetes/kubernetes/pull/87748), [@satyasm](https://github.com/satyasm)) [SIG Cluster Lifecycle,...

* Mark the LBaaS v1 of OpenStack cloud provider deprecated. ([#52821](https://github.com/kubernetes/kubernetes/pull/52821), [@FengyunPan](https://github.com/FengyunPan))
* Mark image as deliberately optional in v1 Container struct.  Many objects in the Kubernetes API inherit the container struct and only Pods require the field to be set. ([#48406](https://github.com/kubernetes/kubernetes/pull/48406), [@gyliu513](https://github.com/gyliu513))

Kubeadm: Automate certificate copy between control planes in HA setups

- Joining control plane nodes to a HA cluster can now be simplified by enabling the optional automatic copy of certificates from an existing control plane node.
- You can now use `kubeadm init --experimental-upload-certs` and `kubeadm join --experimental-control-plane --certificate-key`.

- Mark Job onPodConditions as optional in pod failure policy ([#120210](https://github.com/kubernetes/kubernetes/pull/120210), [@mimowo](https://github.com/mimowo)) [SIG API Machinery and Apps]

### Feature

- Graduated `Job BackoffLimitPerIndex` feature to `beta`. ([#121356](https://github.com/kubernetes/kubernetes/pull/121356), [@mimowo](https://github.com/mimowo))
- Marked the `onPodConditions` field as optional in `Job`'s pod failure policy. ([#120204](https://github.com/kubernetes/kubernetes/pull/120204), [@mimowo](https://github.com/mimowo))

### ConfigMap
* Volumes and environment variables populated from ConfigMap and Secret objects can now tolerate the named source object or specific keys being missing, by adding `optional: true` to the volume or environment variable source specifications. ([#39981](https://github.com/kubernetes/kubernetes/pull/39981), [@fraenkel](https://github.com/fraenkel))

### Cloud Provider

- The GCE-only flag `cloud-provider-gce-lb-src-cidrs` is now optional for external cloud providers. ([#76627](https://github.com/kubernetes/kubernetes/pull/76627), [@timoreimann](https://github.com/timoreimann))

- Added the `access_mode` label to `volume_manager_selinux_*` metrics. ([#123667](https://github.com/kubernetes/kubernetes/pull/123667), [@jsafrane](https://github.com/jsafrane))
- Enhanced cloud provider integrations to support optional, per-Node custom labels that can be supplied and applied to Nodes by the node controller. These extra labels will only be applied where the cloud provider integration supports this feature.