- To enhance usability and developer experience, CRD validation rules now support direct use of (CEL) reserved keywords as field names in object validation expressions.

- Kube-apiserver: Fixed a possible panic validating a custom resource whose `CustomResourceDefinition` indicates a status subresource exists, but which does not define a `status` property in the `openAPIV3Schema`....

### SIG-cluster-lifecycle

In 1.12, SIG Cluster lifecycle has focused on improving the user experience in kubeadm, by fixing a number of bugs and adding some new important features.

Here is a list of some of the changes that have been made to kubeadm:

- Kubeadm internal config has been promoted to `v1alpha3`:

## Changes by Kind

### Bug or Regression

- Fix a bug when the hostname label of a node does not match the node name, pods bound to a PV with nodeAffinity using the hostname may be scheduled to the wrong node or experience scheduling failures. ([#127584](https://github.com/kubernetes/kubernetes/pull/127584), [@AxeZhan](https://github.com/AxeZhan)) [SIG Scheduling and Storage]

    *   SignatureRunner is now supported for models with no signatures.

### SIG Cluster Lifecycle

[kubernetes.tar.gz](https://storage.googleapis.com/kubernetes-release/release/v1.4.0/kubernetes.tar.gz) | `6cf3d78230f7659b87fa399a56a7aaed1fde6a73be9d05e25feedacfbd8d5a16`

## Major Themes

- **Simplified User Experience**
  - Easier to get a cluster up and running (eg: `kubeadm`, intra-cluster bootstrapping)
  - Easier to understand a cluster (eg: API audit logs, server-based API defaults)
- **Stateful Application Support**

* `federation/deploy/deploy.sh` was an interim solution introduced in Kubernetes v1.4 to simplify the federation control plane deployment experience. Now that we have `kubefed`, we are deprecating `deploy.sh` scripts. ([#38902](https://github.com/kubernetes/kubernetes/pull/38902), [@madhusudancs](https://github.com/madhusudancs))


### Cluster Provisioning Scripts

- Added the `DetectCacheInconsistency` feature gate, allowing the API server to periodically verify consistency between its `cache` and `etcd`. Detected inconsistencies reported...

				if took > maxRefreshDurationSecondsForLog {
					// Log if we took a lot of time.
					logger.Info("Site replication healing refresh took %.2fs", took)
				}

				// wait for 200 millisecond, if we are experience lot of I/O
				waitForLowIO(runtime.GOMAXPROCS(0), 200*time.Millisecond, currentHTTPIO)
			}
			healTimer.Reset(siteHealTimeInterval)

		case <-ctx.Done():
			return
		}
	}
}