* etcd3: update etcd godep to 3.0.9 to address TestWatch issues ([#32822](https://github.com/kubernetes/kubernetes/pull/32822), [@timothysc](https://github.com/timothysc))
* etcd3: update to etcd 3.0.10 ([#33393](https://github.com/kubernetes/kubernetes/pull/33393), [@timothysc](https://github.com/timothysc))

* etcd version 2.2.1
  * etcd version 3.0.14 [has also been validated](https://k8s-gubernator.appspot.com/builds/kubernetes-jenkins/logs/ci-kubernetes-e2e-gce-etcd3/) but does require [specific configuration steps](https://coreos.com/blog/migrating-applications-etcd-v3.html)

## Changelog since v1.5.0-beta.3

### Other notable changes

from writing to etcd during an etcd2 -> etcd3 migration.  HA installations cannot
be migrated at the current time using the official Kubernetes procedure.

1.6 will also default to protobuf encoding if using etcd3.  **This change is
irreversible.**  To rollback, you must restore from a backup made before the
protobuf/etcd3 switch, and any changes since the backup will be lost.  As 1.5

  - The deprecated `--etcd-quorum-read` flag has been removed. Quorum reads are now always enabled when fetching data from etcd. Remove the `--etcd-quorum-read` flag from kube-apiserver invocations before upgrading.
- kube-controller-manager
  - The deprecated `--insecure-experimental-approve-all-kubelet-csrs-for-group` flag has been removed.
- kubelet

* Add --etcd-compaction-interval to apiserver for controlling request of compaction to etcd3 from apiserver. ([#51765](https://github.com/kubernetes/kubernetes/pull/51765), [@mitake](https://github.com/mitake))
* Apply algorithm in scheduler by feature gates. ([#52723](https://github.com/kubernetes/kubernetes/pull/52723), [@k82cn](https://github.com/k82cn))

* mark container-port flag as deprecated ([#25072](https://github.com/kubernetes/kubernetes/pull/25072), [@AdoHe](https://github.com/AdoHe))
* Provide flags to use etcd3 backed storage ([#24455](https://github.com/kubernetes/kubernetes/pull/24455), [@hongchaodeng](https://github.com/hongchaodeng))

### Other notable changes

- Update etcd client side to v3.4.4 ([#89169](https://github.com/kubernetes/kubernetes/pull/89169), [@jingyih](https://github.com/jingyih)) [SIG API Machinery and Cloud Provider]
- Update etcd client side to v3.4.7 ([#89822](https://github.com/kubernetes/kubernetes/pull/89822), [@jingyih](https://github.com/jingyih)) [SIG API Machinery and Cloud Provider]

- go.etcd.io/etcd/api/v3: v3.5.0
- go.etcd.io/etcd/client/pkg/v3: v3.5.0
- go.etcd.io/etcd/client/v2: v2.305.0
- go.etcd.io/etcd/client/v3: v3.5.0
- go.etcd.io/etcd/etcdutl/v3: v3.5.0
- go.etcd.io/etcd/pkg/v3: v3.5.0
- go.etcd.io/etcd/raft/v3: v3.5.0
- go.etcd.io/etcd/server/v3: v3.5.0
- go.etcd.io/etcd/tests/v3: v3.5.0

## Known Issues

### Etcd v3.5.[0-2] data corruption

Data corruption issue was found in etcd v3.5.0 release that was shipped with 1.22 Kubernetes release. Please read up-to-date [production recommendations for etcd](https://github.com/etcd-io/etcd/tree/main/CHANGELOG).

## Changes by Kind

### Deprecation

* Fix mounting of UNIX sockets(and other special files) in subpaths ([#61480](https://github.com/kubernetes/kubernetes/pull/61480), [@gnufied](https://github.com/gnufied))
* 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))