### Cluster Lifecycle

- Component-base: make the validation logic about LeaderElectionConfiguration consistent between component-base and client-go ([#111758](https://github.com/kubernetes/kubernetes/pull/111758), [@SataQiu](https://github.com/SataQiu)) [SIG API Machinery and Scheduling]

MUST read this before you upgrade)

- Stopped accepting component configuration for `kube-proxy` and `kubelet` during `kubeadm upgrade plan --config`. This was a legacy behavior that was not well supported for upgrades and could be used only at the plan stage to determine if the configuration for these components stored in the cluster needs manual version migration. In the future, `kubeadm` will attempt alternative component config migration approaches. ([#120788](https://github.com/kube...

### **Instrumentation**
#### Core Metrics API
* [alpha] Introduces a lightweight monitoring component for serving the core resource metrics API used by the Horizontal Pod Autoscaler and other components ([kubernetes/features#271](https://github.com/kubernetes/enhancements/issues/271))


### **Internationalization**

    - [Cluster Autoscaler](#cluster-autoscaler)
    - [Deployment](#deployment)
    - [Federation](#federation)
    - [Internal Storage Layer](#internal-storage-layer)
    - [Node Components](#node-components)
    - [kubectl](#kubectl)
    - [RBAC](#rbac)
    - [Scheduling](#scheduling)
    - [Service](#service)
    - [StatefulSet](#statefulset)
    - [Volumes](#volumes)

- kubeadm: all master components are now exclusively relying on the `PriorityClassName` pod spec for annotating them as cluster critical components. Since `scheduler.alpha.kubernetes.io/critical-pod` annotation is no longer supported by Kubernetes 1.14 this annotation is no longer added to master components. ([#73857](https://github.com/kubernetes/kubernetes/pull/73857), [@ereslibre](https://github.com/ereslibre))...

* Kubelet: Periodically reporting image pulling progress in log ([#26145](https://github.com/kubernetes/kubernetes/pull/26145), [@Random-Liu](https://github.com/Random-Liu))

- If upgrading Cluster Federation components from 1.3.x, please ensure your cluster name is a valid DNS label (#30956, @nikhiljindal)
- kubelet's `--config` flag has been deprecated, use `--pod-manifest-path` instead (#29999, @mtaufen)