- Kubelet's deprecated `--experimental-kernel-memcg-notification` flag is now...

* "kubeadm init" now writes a structured and versioned kubelet ComponentConfiguration file to `/var/lib/kubelet/config.yaml` and an environment file with runtime flags that you can source in the systemd kubelet dropin to `/var/lib/kubelet/kubeadm-flags.env`. ([#63887](https://github.com/kubernetes/kubernetes/pull/63887), [@luxas](https://github.com/luxas))

				"application/vemmi",
				"application/vividence.scriptfile",
				"application/vnd.3gpp.bsf+xml",
				"application/vnd.3gpp.pic-bw-large",
				"application/vnd.3gpp.pic-bw-small",
				"application/vnd.3gpp.pic-bw-var",
				"application/vnd.3gpp.sms",
				"application/vnd.3gpp2.bcmcsinfo+xml",
				"application/vnd.3gpp2.sms",
				"application/vnd.3gpp2.tcap",
				"application/vnd.3m.post-it-notes",

  - Speed up binpacking by reducing the number of PreFilter calls (call once per pod instead of #pods*#nodes times)
  - Speed up finding unneeded nodes by 5x+ in very large clusters by reducing the number of PreFilter calls
  - Expose `--max-nodes-total` as a metric
  - Errors in `IncreaseSize` changed from type `apiError` to `cloudProviderError`

### Bug or Regression

- Kube-apiserver: gzip compression switched from level 4 to level 1 to improve large list call latencies in exchange for higher network bandwidth usage (10-50% higher). This increases the headroom before very large unpaged list calls exceed request timeout limits. ([#112400](https://github.com/kubernetes/kubernetes/pull/112400), [@shyamjvs](https://github.com/shyamjvs)) [SIG API Machinery]

    1. Generate a `/var/lib/kubelet/instance-config.yaml` file to customize the `containerRuntimeEndpoint` field in per-node kubelet configurations.
    2. Remove the `kubeadm.alpha.kubernetes.io/cri-socket` annotation from nodes during upgrade operations.

    val out = stream.sink.buffer()
    out.write(buff)
    out.flush()
    out.close()
    val synStream = peer.takeFrame()
    assertThat(synStream.type).isEqualTo(Http2.TYPE_HEADERS)
    var data = peer.takeFrame()
    assertThat(data.data!!.size).isEqualTo(peer.maxOutboundDataLength())
    data = peer.takeFrame()
    assertThat(data.data!!.size).isEqualTo(1)
  }

  @Test fun pushPromiseStream() {

* Kubeadm is currently omitting etcd certificates in a self-hosted deployment; this will be fixed in a point relelase. ([#61322](https://github.com/kubernetes/kubernetes/issues/61322))

* Some users, especially those with very large clusters, may see higher memory usage by the kube-controller-manager in 1.10. ([#61041](https://github.com/kubernetes/kubernetes/issues/61041))

      * Added exported env vars to kubectl plugins so that plugin developers have access to global flags, namespace, the plugin descriptor and the full path to the caller binary.

  * Enhancement

backwards-incompatible changes, most of which are rare use cases, bug fixes with side effects, or things that have been deprecated for multiple releases already:
  
  - https://github.com/kubernetes-sigs/kustomize/pull/4911: Drop support for a very old, legacy style of patches. patches used to be allowed to be used as an alias for patchesStrategicMerge in kustomize v3. You now have to use patchesStrategicMerge explicitly, or update to the new syntax supported by patches. See examples in the PR...