- 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))

- Single static pod files and pod files from http endpoints cannot be larger than 10 MB. HTTP probe payloads are now truncated to 10KB. ([#82669](https://github.com/kubernetes/kubernetes/pull/82669), [@rphillips](https://github.com/rphillips))

* 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))

    * 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.

* Kubelet now exposes a new endpoint, `/metrics/probes`, which exposes a Prometheus metric containing the liveness and/or readiness probe results for a container. ([#61369](https://github.com/kubernetes/kubernetes/pull/61369), [@rramkumar1](https://github.com/rramkumar1))

### SIG Network