- On single-stack configured (IPv4 or IPv6, but not both) clusters, Services which are both headless (no clusterIP) and selectorless (empty or undefined selector) will report `ipFamilyPolicy RequireDualStack` and will have entries in `ipFamilies[]` for both IPv4 and IPv6.  This is a change from alpha, but does not have any impact on the manually-specified Endpoints and EndpointSlices for the Service. (...

- Scheduler alpha metrics binding_duration_seconds and scheduling_algorithm_preemption_evaluation_seconds are deprecated, Both of those metrics are now covered as part of framework_extension_point_duration_seconds, the former as a PostFilter the latter and a Bind plugin. The plan is to remove both in 1.21 ([#95001](https://github.com/kubernetes/kubernetes/pull/95001), [@arghya88](https://github.com/arghya88)) [SIG Instrumentation and Scheduling]

  - **apiserver_flowcontrol_priority_level_seat_count_watermarks**: histograms of high and low watermarks of number of seats occupied by executing requests (both regular and final-delay phases included), broken down by priority_level.

- Structured logging of NamespacedName was inconsistent with klog.KObj. Now both use lower case field names and namespace is optional. ([#117238](https://github.com/kubernetes/kubernetes/pull/117238), [@pohly](https://github.com/pohly)) [SIG API Machinery, Architecture and Instrumentation]

## Dependencies

- [IPv4/IPv6 dual-stack](https://kubernetes.io/docs/concepts/services-networking/dual-stack) enables the allocation of both IPv4 and IPv6 addresses to Pods and Services.
- [API Server Network Proxy](https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/1281-network-proxy/README.md) going alpha in 1.16.

## Urgent Upgrade Notes
### (No, really, you MUST read this before you upgrade)
#### Cluster Lifecycle

### Extensibility around core Kubernetes APIs

#### CustomResourceDefinitions Pruning

* Fix kube-apiserver crash when patching TPR data ([#44612](https://github.com/kubernetes/kubernetes/pull/44612), [@nikhita](https://github.com/nikhita))

- github.com/armon/go-radix: [7fddfc3](https://github.com/armon/go-radix/tree/7fddfc3)
- github.com/bgentry/speakeasy: [v0.1.0](https://github.com/bgentry/speakeasy/tree/v0.1.0)
- github.com/bits-and-blooms/bitset: [v1.2.0](https://github.com/bits-and-blooms/bitset/tree/v1.2.0)
- github.com/bketelsen/crypt: [v0.0.4](https://github.com/bketelsen/crypt/tree/v0.0.4)

* falls back to parse Docker runtime version as generic if not semver ([#54040](https://github.com/kubernetes/kubernetes/pull/54040), [@dixudx](https://github.com/dixudx))
* BUG FIX: Check both name and ports for azure health probes ([#56918](https://github.com/kubernetes/kubernetes/pull/56918), [@feiskyer](https://github.com/feiskyer))



# v1.8.5