- 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))

## Dependencies

### Added
- github.com/antihax/optional: [v1.0.0](https://github.com/antihax/optional/tree/v1.0.0)
- github.com/benbjohnson/clock: [v1.0.3](https://github.com/benbjohnson/clock/tree/v1.0.3)
- github.com/bits-and-blooms/bitset: [v1.2.0](https://github.com/bits-and-blooms/bitset/tree/v1.2.0)

- Expanded the on-disk kubelet credential provider configuration to allow an optional `tokenAttribute` field to be configured. When it is set, the kubelet will provision a token with the given audience bound to the current pod and its service account. This KSA token along with required annotations on the KSA defined in configuration...

     &^          &^=          ~
</pre>

<h3 id="Integer_literals">Integer literals</h3>

<p>
An integer literal is a sequence of digits representing an
<a href="#Constants">integer constant</a>.
An optional prefix sets a non-decimal base: <code>0b</code> or <code>0B</code>
for binary, <code>0</code>, <code>0o</code>, or <code>0O</code> for octal,
and <code>0x</code> or <code>0X</code> for hexadecimal

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`.

- 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,...

- The name of CEL(Common Expression Language) optional type has been changed from `optional` to `optional_type`. ([#124328](https://github.com/kubernetes/kubernetes/pull/124328), [@jiahuif](https://github.com/jiahuif)) [SIG API Machinery, Architecture, Auth, CLI, Cloud Provider, Network and Node]

- Property `conditions` in `apiextensions.v1beta1.CustomResourceDefinitionStatus` and `apiextensions.v1.CustomResourceDefinitionStatus` is now optional instead of required. ([#64996](https://github.com/kubernetes/kubernetes/pull/64996), [@roycaihw](https://github.com/roycaihw))

- EmptyDir memory backed volumes are sized as the minimum of pod allocatable memory on a host and an optional explicit user provided value. ([#100319](https://github.com/kubernetes/kubernetes/pull/100319), [@derekwaynecarr](https://github.com/derekwaynecarr)) [SIG Node]

### 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))