### ConfigMap
* Volumes and environment variables populated from ConfigMap and Secret objects can now tolerate the named source object or specific keys being missing, by adding `optional: true` to the volume or environment variable source specifications. ([#39981](https://github.com/kubernetes/kubernetes/pull/39981), [@fraenkel](https://github.com/fraenkel))

- Added HPA support to pod-level resource specifications. When the pod-level resource feature was enabled, HPAs configured with `Resource` type metrics calculated the pod resources from `pod.Spec.Resources` field, if specified. ([#132430](https://github.com/kubernetes/kubernetes/pull/132430), [@lao...

- Considerably reduced the CPU load in kube-apiserver while aggregating OpenAPI specifications from aggregated API servers. ([#71223](https://github.com/kubernetes/kubernetes/pull/71223), [@sttts](https://github.com/sttts))

In addition, users can now create multiple versions of CustomResourceDefinitions, but without any kind of automatic conversion, and CustomResourceDefinitions now allow specification of additional columns for `kubectl get` output via the `spec.additionalPrinterColumns` field.

### SIG Auth

1) Alpha for AWS ALB (Application Load Balancer) integration to Kubernetes Ingress resources.
2) Alpha for CSI specification 0.3 integration to AWS EBS (Elastic Block Store)

- Removed the networking `alpha` API `ClusterCIDR`. ([#121229](https://github.com/kubernetes/kubernetes/pull/121229),...

use to accurately and efficiently track set membership across `apply` operations. The format used for `ApplySet` is set out in  [KEP 3659](https://github.com/kubernetes/enhancements/issues/3659) as a low-level specification.  Other tools in the ecosystem can also build on this specification for improved interoperability.  To try the ApplySet-based pruning alpha, set `KUBECTL_APPLYSET=true` and use the flags `--prune --applyset=secret-name` with `kubectl apply`. ([#116205](https://github.com/kuber...

- In a future release, kubelet will no longer create the CSI NodePublishVolume target directory, in accordance with the CSI specification. CSI drivers may need to be updated accordingly to properly create and process the target path. ([#75535](https://github.com/kubernetes/kubernetes/issues/75535)) [SIG Storage]

#### kube-proxy:

m/ijc))

* kubeadm: New "imagePullPolicy" option in the init configuration file, that gets forwarded to kubelet static pods to control pull policy for etcd and control plane images. This option allows for precise image pull policy specification for master nodes and thus for more tight control over images. It is useful in CI environments and in environments, where the user has total control over master VM templates (thus, the master VM templates can be preloaded with the required Docker...

### Promoted CSI Ephemeral Volume to Stable