- Promote CSIMigrationOpenStack to Beta (off by default since it requires installation of the OpenStack Cinder CSI Driver. The in-tree AWS OpenStack Cinder driver "kubernetes.io/cinder" was deprecated in 1.16 and will be removed in 1.20. Users should enable CSIMigration + CSIMigrationOpenStack features and install the OpenStack Cinder CSI Driver (https://github.com/kubernetes/cloud-provider-openstack) to avoid disruption to existing Pod and PVC objects at that time....

## Notable Features

- Increased the histogram resolution of the API server client certificate  to accommodate short-lived (< 6h) client certificates. ([#74806](https://github.com/kubernetes/kubernetes/pull/74806), [@mxinden](https://github.com/mxinden))
- Updated to use golang 1.12 ([#74632](https://github.com/kubernetes/kubernetes/pull/74632), [@cblecker](https://github.com/cblecker))

 - OpenStack Cinder CSI migration is on by default, Clinder CSI driver must be installed on clusters on OpenStack for Cinder volumes to work. ([#98538](https://github.com/kubernetes/kubernetes/pull/98538), [@dims](https://github.com/dims)) [SIG Storage]

* fixes a bug around using the Global config ElbSecurityGroup where Kuberentes would modify the passed in Security Group. ([#49805](https://github.com/kubernetes/kubernetes/pull/49805), [@nbutton23](https://github.com/nbutton23))
* Updates Cinder AttachDisk operation to be more reliable by delegating Detaches to volume manager. ([#50042](https://github.com/kubernetes/kubernetes/pull/50042), [@jingxu97](https://github.com/jingxu97))

### **OpenStack**

*   OpenStack Cinder support has been improved:
    *   Cinder version detection now works properly. ([#53115](https://github.com/kubernetes/kubernetes/pull/53115),[ @FengyunPan](https://github.com/FengyunPan))

- New flag `--show-hidden-metrics-for-version` in kube-apiserver can be used to show all hidden metrics that deprecated in the previous minor release. ([#84292](https://github.com/kubernetes/kubernetes/pull/84292), [@RainbowMango](https://github.com/RainbowMango))

* Make volume usage metrics available for Cinder ([#62668](https://github.com/kubernetes/kubernetes/pull/62668), [@zetaab](https://github.com/zetaab))

  when the corresponding csi driver was installed:
  - `awsElasticBlockStore` for `ebs.csi.aws.com`
  - `azureDisk` for `disk.csi.azure.com`
  - `gcePersistentDisk` for `pd.csi.storage.googleapis.com`
  - `cinder` for `cinder.csi.openstack.org`
  - `csi`
  However it was still enforced using a limit in CSINode objects. ([#126924](https://github.com/kubernetes/kubernetes/pull/126924), [@carlory](https://github.com/carlory))

  * kubectl describe no longer prints the last-applied-configuration annotation for secrets. ([#34664](https://github.com/kubernetes/kubernetes/pull/34664), [@ymqytw](https://github.com/ymqytw))
  * Completed pods should not be hidden when requested by name via `kubectl get`. ([#42216](https://github.com/kubernetes/kubernetes/pull/42216), [@smarterclayton](https://github.com/smarterclayton))

* PVC may not be synced to controller local cache in time if PV is bound by external PV binder (e.g. kube-scheduler), double check if PVC is not found to prevent reclaiming PV wrongly. ([#67062](https://github.com/kubernetes/kubernetes/pull/67062), [@cofyc](https://github.com/cofyc))