### **Cluster Lifecycle**

*   kube-apiserver: `--ssh-user` and `--ssh-keyfile` are now deprecated and will be removed in a future release. Users of SSH tunnel functionality in Google Container Engine for the Master -> Cluster communication should plan alternate methods for bridging master and node networks. ([#54433](https://github.com/kubernetes/kubernetes/pull/54433),[ @dims](https://github.com/dims))

* Ensure euqiv hash calculation is per schedule ([#59245](https://github.com/kubernetes/kubernetes/pull/59245), [@resouer](https://github.com/resouer))

* Upped the timeout for apiserver communication in the juju kubernetes-worker charm. ([#59219](https://github.com/kubernetes/kubernetes/pull/59219), [@hyperbolic2346](https://github.com/hyperbolic2346))

- Resolves bottleneck in internal API server communication that can cause increased goroutines and degrade API Server performance ([#80465](https://github.com/kubernetes/kubernetes/pull/80465), [@answer1991](https://github.com/answer1991))

* Introduce policy to allow the HPA to consume the metrics.k8s.io and custom.metrics.k8s.io API groups. ([#52572](https://github.com/kubernetes/kubernetes/pull/52572), [@DirectXMan12](https://github.com/DirectXMan12))
* kubelet to master communication when doing node status updates now has a timeout to prevent indefinite hangs ([#52176](https://github.com/kubernetes/kubernetes/pull/52176), [@liggitt](https://github.com/liggitt))

* Resolves bottleneck in internal API server communication that can cause increased goroutines and degrade API Server performance ([#80465](https://github.com/kubernetes/kubernetes/pull/80465), [@answer1991](https://github.com/answer1991))

following in mind:

* **JSON configuration files that contain fields with incorrect case will no longer be valid. You must correct these files before upgrading.** When specifying keys in JSON resource definitions during direct API server communication, the keys are case-sensitive. A bug introduced in Kubernetes 1.8 caused the API server to accept a request with incorrect case and coerce it to correct case, but this behaviour has been fixed in 1.11 and the API server will once again be enforcing...

`docker` service from kubeadm preflight. Docker is no longer special cased during host validation and ideally this task should be done in the now external cri-dockerd project where the importance of the compatibility matters. Use `crictl` for all communication with CRI sockets for actions like pulling images and obtaining a list of running containers instead of using the docker CLI in the case of Docker. ([#107317](https://github.com/kubernetes/kubernetes/pull/107317), [@neolit123](https://github.com/neolit123))...

* Fixes a panic in kube-controller-manager cleaning up bootstrap tokens ([#82887](https://github.com/kubernetes/kubernetes/pull/82887), [@tedyu](https://github.com/tedyu))
* Resolves bottleneck in internal API server communication that can cause increased goroutines and degrade API Server performance ([#80465](https://github.com/kubernetes/kubernetes/pull/80465), [@answer1991](https://github.com/answer1991))

* Update to go 1.12.10 ([#83139](https://github.com/kubernetes/kubernetes/pull/83139), [@cblecker](https://github.com/cblecker))
* Resolves bottleneck in internal API server communication that can cause increased goroutines and degrade API Server performance ([#80465](https://github.com/kubernetes/kubernetes/pull/80465), [@answer1991](https://github.com/answer1991))

  * **WARNING:** A [known issue](https://github.com/kubernetes/kubernetes/issues/43815)
    in v1.6.0 causes `kubeadm init` to hang. Please use v1.6.1, which fixes the issue.
  * All communication is now over TLS
  * Authorization plugins can be installed by kubeadm, including the new default of RBAC
  * The bootstrap token system now allows token management and expiration