* kube-apiserver: requests to endpoints handled by unavailable extension API servers (as indicated by an `Available` condition of `false` in the registered APIService) now return `503` errors instead of `404` errors. ([#58070](https://github.com/kubernetes/kubernetes/pull/58070), [@weekface](https://github.com/weekface))

- kube-apiserver now includes all registered API groups in discovery, including registered extension API group/versions for unavailable extension API servers. ([#66932](https://github.com/kubernetes/kubernetes/pull/66932), [@nilebox](https://github.com/nilebox))

- Fix bug that would let the Horizontal Pod Autoscaler scale down despite at least one metric being unavailable/invalid ([#99514](https://github.com/kubernetes/kubernetes/pull/99514), [@mikkeloscar](https://github.com/mikkeloscar)) [SIG Apps and Autoscaling]

- Kubeadm: improved retries when updating node information, in case `kube-apiserver` is temporarily unavailable ([#114176](https://github.com/kubernetes/kubernetes/pull/114176), [@QuantumEnergyE](https://github.com/QuantumEnergyE))

*   Azure NSG rules can be consolidated to reduce the likelihood of hitting Azure resource limits (available only in regions where the Augmented Security Groups preview is available).  ([#55740](https://github.com/kubernetes/kubernetes/pull/55740), [@itowlson](https://github.com/itowlson))

* [stable] Expose storage usage metrics

  * The available capacity of a given Persistent Volume (PV) is available by calling the Kubernetes metrics API.

* [stable] Volume plugin metrics

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