`autoscaling/v2alpha1`. The Horizontal Pod Autoscaler changes include support for status conditions, and autoscaling on memory and custom metrics.

* The metrics APIs, `custom-metrics.metrics.k8s.io` and `metrics`, were moved from `v1alpha1` to `v1beta1`, and renamed to `custom.metrics.k8s.io` and `metrics.k8s.io`, respectively. If you have deployed a custom metrics adapter, ensure that it supports the new API version. If you have deployed Heapster in aggregated API server mode, upgrade...

* kubectl could scale custom resource again ([#81342](https://github.com/kubernetes/kubernetes/pull/81342), [@knight42](https://github.com/knight42))

    - [**API Machinery**](#api-machinery-3)
      - [**Admission Control**](#admission-control)
      - [**API & API server**](#api-&-api-server)
      - [**Audit**](#audit)
      - [**Custom Resources**](#custom-resources)
      - [**Other**](#other)
    - [**Apps**](#apps-1)
    - [**Auth**](#auth-3)
      - [**Audit**](#audit-1)
      - [**RBAC**](#rbac)
      - [**Other**](#other-1)
      - [**GCE**](#gce)

- Fixes an issue that can result in namespaced custom resources being orphaned when their namespace is deleted, if the CRD defining the custom resource is removed concurrently with namespaces being deleted, then recreated. ([#93790](https://github.com/kubernetes/kubernetes/pull/93790), [@liggitt](https://github.com/liggitt)) [SIG API Machinery...

- The rules for incrementing `metadata.generation` of custom resources changed: ([#69059](https://github.com/kubernetes/kubernetes/pull/69059), [@caesarxuchao](https://github.com/caesarxuchao))
  - If the custom resource participates the spec/status convention, the metadata.generation of the CR increments when there is any change, except for the changes to the metadata or the changes to the status.

    * Custom apiservers built with the latest apiserver library will have the 100MB limit on the body of resource requests as well. The limit can be altered via ServerRunOptions.MaxRequestBodyBytes.

- Fixes conversion error in multi-version custom resources that could cause metadata.generation to increment on no-op patches or updates of a custom resource. ([#88995](https://github.com/kubernetes/kubernetes/pull/88995), [@liggitt](https://github.com/liggitt)) [SIG API Machinery]

- Fixes a bug at kube-apiserver start where APIService objects for custom resources could be deleted and recreated. ([#118104](https://github.com/kubernetes/kubernetes/pull/118104), [@liggitt](https://github.com/liggitt)) [SIG API Machinery and Testing]

- Now users can get object info like:

  ```bash
    a. kubectl get pod test-pod -o custom-columns=CONTAINER:.spec.containers[0:3].name
    b. kubectl get pod test-pod -o custom-columns=CONTAINER:.spec.containers[-2:].name
  ```

([#73063](https://github.com/kubernetes/kubernetes/pull/73063), [@WanLinghao](https://github.com/WanLinghao))

  
  Action required for custom scheduler plugin developers:
  Plugins **have to** implement a QueueingHint for Pod/Update event if the rejection from them could be resolved by updating unscheduled Pods themselves.
  Example: suppose you develop a custom plugin that denies Pods that have a `schedulable=false` label.