- Kubeadm: Switched to using the new etcd endpoints introduced in 3.5.11 - /livez (for liveness probe) and /readyz (for readyness and startup probe). With this change it is no longer possible to deploy a custom etcd version older than 3.5.11 with kubeadm 1.31. If so, please upgrade etcd to a supported version. ([#124465](https://github.com/kubernetes/kubernetes/pull/124465),...

    * Bump metadata agent version to 0.2-0.0.21-1.
    * Expand the metadata agent's access to all API groups.
    * Remove metadata agent config maps in favor of command line flags.
    * Update the metadata agent's liveness probe to a new /healthz handler.
    * Logging Agent Improvements
    * Bump logging agent version to 0.2-1.5.33-1-k8s-1.
    * Appropriately set log severity for k8s_container.

* allow group impersonation ([#30803](https://github.com/kubernetes/kubernetes/pull/30803), [@deads2k](https://github.com/deads2k))
* Always return command output for exec probes and kubelet RunInContainer ([#30731](https://github.com/kubernetes/kubernetes/pull/30731), [@ncdc](https://github.com/ncdc))

* addon-resizer flapping behavior was removed. ([#46850](https://github.com/kubernetes/kubernetes/pull/46850), [@x13n](https://github.com/x13n))
* Change default `httpGet` probe `User-Agent` to `kube-probe/<version major.minor>` if none specified, overriding the default Go `User-Agent`. ([#47729](https://github.com/kubernetes/kubernetes/pull/47729), [@paultyng](https://github.com/paultyng))

## Changelog since v1.18.18

## Changes by Kind

### API Change

- We have added a new Priority & Fairness rule that exempts all probes (/readyz, /healthz, /livez) to prevent 
  restarting of "healthy" kube-apiserver instance(s) by kubelet. ([#101114](https://github.com/kubernetes/kubernetes/pull/101114), [@tkashem](https://github.com/tkashem)) [SIG API Machinery]

* vSphere kube-up: Wait for cbr0 configuration to complete before setting up routes. ([#35232](https://github.com/kubernetes/kubernetes/pull/35232), [@kerneltime](https://github.com/kerneltime))
* Remove last probe time from replica sets ([#35199](https://github.com/kubernetes/kubernetes/pull/35199), [@kargakis](https://github.com/kargakis))

* BUG FIX: Check both name and ports for azure health probes ([#56918](https://github.com/kubernetes/kubernetes/pull/56918), [@feiskyer](https://github.com/feiskyer))

* Flush conntrack state for removed/changed UDP Services ([#22573](https://github.com/kubernetes/kubernetes/pull/22573), [@freehan](https://github.com/freehan))
* Allow setting the Host header in a httpGet probe ([#24292](https://github.com/kubernetes/kubernetes/pull/24292), [@errm](https://github.com/errm))

  - Fix a data race in TopologyCache when `AddHints` and `SetNodes` are called concurrently ([#117268](https://github.com/kubernetes/kubernetes/pull/117268), [@tnqn](https://github.com/tnqn)) [SIG Apps and Network]
- Revert kubelet prober metrics `pod` tag to include actual pod name ([#118549](https://github.com/kubernetes/kubernetes/pull/118549), [@a7i](https://github.com/a7i)) [SIG Node]

- Fixed a bug that unintentionally overrides custom Accept headers in http (live-/readiness)-probes if the header is in lowercase. ([#114606](https://github.com/kubernetes/kubernetes/pull/114606), [@tuunit](https://github.com/tuunit))