## 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]

### Bug or Regression

  [overwrite of manual edits to GCP Health Checks](https://github.com/kubernetes/ingress/issues/842)
  managed by the GLBC Ingress Controller. This can cause the health checks to start failing,
  requiring you to reapply the manual edits.
  * This issue does not affect clusters that were already running Kubernetes v1.6.4 or higher.
  * This issue does not affect Health Checks that were left in the configuration

During server startup, prior to the server reporting healthy (via `/healthz`), not all API groups may be reported.
Wait for the server to report healthy (via `/healthz`) before depending on the information provided by the discovery APIs.

components, but only worked when those components were local to the API server, and when kube-scheduler and kube-controller-manager exposed unsecured health endpoints. Instead of this API, etcd health is included in the kube-apiserver health check and kube-scheduler/kube-controller-manager health checks can be made directly against those components' health endpoints. ([#93570](https://github.com/kubernetes/kubernetes/pull/93570), [@liggitt](https://github.com/liggitt)) [SIG API Machinery, Apps and Cluster...

- If `ComponentSLIs` feature gate is enabled, then `/metrics/slis` now becomes available on cloud-controller-manager allowing you to scrape health check metrics. ([#113340](https://github.com/kubernetes/kubernetes/pull/113340), [@Richabanker](http...

- kubeadm: use etcd's /health endpoint for a HTTP liveness probe on localhost instead of having a custom health check using etcdctl ([#81385](https://github.com/kubernetes/kubernetes/pull/81385), [@neolit123](https://github.com/neolit123))

- Exposed the kube-scheduler "/livez" and "/readz" endpoints for health checks that are in compliance with https://kubernetes.io/docs/reference/using-api/health-checks/#api-endpoints-for-health. ([#118148](https://github.com/kubernetes/kubernetes/pull/118148), [@linxiulei](https://github.com/linxiulei)) [SIG API Machinery, Scheduling and Testing]

    *  -  the `health` plugin now includes the `lameduck` option by default, which waits for a duration before shutting down.
* Kubeadm now includes CoreDNS version 1.6.5 ([#85108](https://github.com/kubernetes/kubernetes/pull/85108), [@rajansandeep](https://github.com/rajansandeep))
    *  - `kubernetes` plugin adds metrics to measure kubernetes control plane latency.

message ComponentCondition {
  // Type of condition for a component.
  // Valid value: "Healthy"
  optional string type = 1;

  // Status of the condition for a component.
  // Valid values for "Healthy": "True", "False", or "Unknown".
  optional string status = 2;

  // Message about the condition for a component.
  // For example, information about a health check.
  // +optional
  optional string message = 3;

- Kubeadm: modified the etcd static Pod `liveness` and `readiness` probes to use a new etcd `v3.5.3+` HTTP(s) health check endpoint `/health?serializable=true` that allows to track the health of individual etcd members and not fail all members if a single member is not healthy in the etcd cluster. ([#110072](https://github.com/kubernetes/kubernetes/pull/110072), [@neolit123](https://github.com/neolit123))