## Before Upgrading

* If you need to downgrade from 1.10 to 1.9.x, downgrade to v1.9.6 to ensure PV and PVC objects can be deleted properly.

  This feature will not be fully enabled until a future Kubernetes release (likely to be v1.29), but is added in v1.28 to enable
  safe rollback on downgrade. ([#118339](https://github.com/kubernetes/kubernetes/pull/118339), [@jpbetz](https://github.com/jpbetz)) [SIG API Machinery, Auth, Cloud Provider and Testing]

## Introduction to 1.9.0

    * To downgrade the cluster to version that does not support scale-to-zero feature:
    * 1. make sure there are no hpa objects with minReplicas=0. Here is a oneliner to update it to 1:

- Support a smooth upgrade from client-side apply to server-side apply without conflicts, as well as support the corresponding downgrade. ([#90187](https://github.com/kubernetes/kubernetes/pull/90187), [@julianvmodesto](https://github.com/julianvmodesto)) [SIG API Machinery and Testing]

- fluentd-elasticsearch is unchanged from 1.10: v2.0.4 ([#58525](https://github.com/kubernetes/kubernetes/pull/58525))
- The fluent-plugin-kubernetes_metadata_filter plugin in fluentd-elasticsearch has been downgraded to version 2.0.0 ([#67544](https://github.com/kubernetes/kubernetes/pull/67544))
- fluentd-gcp is unchanged from 1.10: v3.0.0. ([#60722](https://github.com/kubernetes/kubernetes/pull/60722))

* Fix GCE etcd scripts to pass in all required parameters for the etcd migration utility to correctly perform HA upgrades and downgrades ([#61957](https://github.com/kubernetes/kubernetes/pull/61957), [@jpbetz](https://github.com/jpbetz))