- The `batch/v2alpha1` CronJob type definitions and clients are deprecated and removed. ([#96987](https://github.com/kubernetes/kubernetes/pull/96987), [@soltysh](https://github.com/soltysh)) [SIG API Machinery, Apps, CLI and Testing]

* NodeNotReady on failed PLEG health check.
  ([#41569](https://github.com/kubernetes/kubernetes/pull/41569),
  [@yujuhong](https://github.com/yujuhong))
* CRI: upgrade protobuf to v3. Protobuf v2 and v3 are not compatible.
  ([#39158](https://github.com/kubernetes/kubernetes/pull/39158), [@feiskyer](https://github.com/feiskyer))

* Stackdriver cluster logging now deploys a new component to export Kubernetes events. ([#46700](https://github.com/kubernetes/kubernetes/pull/46700), [@crassirostris](https://github.com/crassirostris))

* Stackdriver Logging deployment exposes metrics on node port 31337 when enabled. ([#47402](https://github.com/kubernetes/kubernetes/pull/47402), [@crassirostris](https://github.com/crassirostris))

## Other notable changes

### API Machinery

- Added port configuration to Admission webhook configuration service reference.
- Added port configuration to AuditSink webhook configuration service reference.
- Added port configuration to CRD Conversion webhook configuration service reference.

Service Level Indicators (SLIs) and Service Level Objectives (SLOs) for the system.
Here's the release [scalability validation report].

[SIG Scalability]: https://github.com/kubernetes/community/tree/master/sig-scalability
[scalability validation report]: https://github.com/kubernetes/sig-release/blob/master/releases/release-1.8/scalability_validation_report.md

### SIG Scheduling

- Kubeadm: add the deprecated flag --port=0 to kube-controller-manager and kube-scheduler manifests to disable insecure serving. Without this flag the components by default serve (e.g. /metrics) insecurely on the default node interface (controlled by --address). Users that wish to override this behavior and enable insecure serving can pass a custom --port=X via kubeadm's "extraArgs" mechanic for these components. ([#92720](https://github.com/k...

 
## Changes by Kind

### Deprecation

- Controller-manager: the following flags have no effect and would be removed in v1.24:
  - `--port`
  - `--address`
  The insecure port flags `--port` may only be set to 0 now.
  
  In addtion, please be careful that:

- github.com/hashicorp/serf: [v0.8.2](https://github.com/hashicorp/serf/tree/v0.8.2)
- github.com/jpillora/backoff: [v1.0.0](https://github.com/jpillora/backoff/tree/v1.0.0)
- github.com/jstemmer/go-junit-report: [v0.9.1](https://github.com/jstemmer/go-junit-report/tree/v0.9.1)
- github.com/kr/logfmt: [b84e30a](https://github.com/kr/logfmt/tree/b84e30a)
- github.com/kr/pty: [v1.1.1](https://github.com/kr/pty/tree/v1.1.1)

### Action Required

* New GCE or GKE clusters created with `cluster/kube-up.sh` will not enable the legacy ABAC authorizer by default. If you would like to enable the legacy ABAC authorizer, export ENABLE_LEGACY_ABAC=true before running `cluster/kube-up.sh`. ([#51367](https://github.com/kubernetes/kubernetes/pull/51367), [@cjcullen](https://github.com/cjcullen))

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