- Pod status updates faster when reacting on probe results. The first readiness probe will be called faster when startup probes succeeded, which will make Pod status as ready faster. ([#98376](https://github.com/kubernetes/kubernetes/pull/98376), [@matthyx](https://github.com/matthyx))

- 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]

    * 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.

* Free up CPU and memory requested but unused by Metrics Server Pod Nanny. ([#57252](https://github.com/kubernetes/kubernetes/pull/57252), [@kawych](https://github.com/kawych))
* Configurable liveness probe initial delays for etcd and kube-apiserver in GCE ([#57749](https://github.com/kubernetes/kubernetes/pull/57749), [@wojtek-t](https://github.com/wojtek-t))

* 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]

- 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))

- A bug was fixed in kubelet where exec probe timeouts were not respected. This may result in unexpected behavior since the default timeout (if not specified) is `1s` which may be too small for some exec probes. Ensure that pods relying on this behavior are updated to correctly handle probe timeouts. See [configure probe](https://docs.k8s.io/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/#configure-probes) section of the documentation for more details.

- Fix: ignore non-VMSS error for VMAS nodes in `reconcileBackendPools`. ([#103997](https://github.com/kubernetes/kubernetes/pull/103997), [@nilo19](https://github.com/nilo19))
- Fix: leave the probe path empty for TCP probes ([#105253](https://github.com/kubernetes/kubernetes/pull/105253), [@nilo19](https://github.com/nilo19))

- Kubeadm: make sure the etcd static pod startup probe uses /health?serializable=false while the liveness probe uses /health?serializable=true&exclude=NOSPACE. The NOSPACE exclusion would allow administrators to address space issues one member at a time. ([#110744](https://github.com/kubernetes/kubernetes/pull/110744), [@neolit1...