- Added new option to the `InterPodAffinity` scheduler plugin to ignore existing
  pods` preferred inter-pod affinities if the incoming pod has no preferred inter-pod
  affinities. This option can be used as an optimization for higher scheduling throughput
  (at the cost of an occasional pod being scheduled non-optimally/violating existing
  pods preferred inter-pod affinities). To enable this scheduler option, set the

Jobs (instead of Pods) by default.
  * Pods can now consume Secret data in environment variables and inject those
environment variables into a container’s command-line args.
  * Stable version of Heapster which scales up to 1000 nodes: more metrics, reduced
latency, reduced cpu/memory consumption (~4mb per monitored node).
  * Pods now have a security context which allows users to specify:

  Similarly you can also access  kubelet's `/pods` endpoint to fetch a list of Pods bound to that node by granting the caller `nodes/pods` permission in RBAC.
  Similarly you can also access kubelet's `/configz` endpoint to fetch kubelet's configuration by granting the caller `nodes/configz` permission in RBAC.

affinity/anti-affinity](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/) and **[beta]** [pod affinity/anti-affinity](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/). Node affinity/anti-affinity allow you to specify rules for restricting which node(s) a pod can schedule onto, based on the labels on the node. Pod affinity/anti-affinity allow you to specify rules for spreading and packing pods relative to one another, across arbitrary topologies (node, zone, etc.) These...

    * Specifically the new controller watches the API server for scheduled pods. It processes each pod and ensures that any volumes that implement the volume Attacher interface are attached to the node their pod is scheduled to.

- Added support to the scheduler to start using QueueingHint registered for Pod/Updated event to determine whether unschedulable Pods update make them schedulable, when the feature gate `SchedulerQueueingHints` is enabled.
  Previously, when unschedulable Pods are updated, the scheduler always put Pods back to activeQ/backoffQ. But, actually not all updates to Pods make Pods schedulable, especially considering many scheduling constraints nowadays are immutable.

      * In 1.4, either that key or this key: `pods.beta.kubernetes.io/init-containers`,can be used.
    * When you GET an object, you will see both annotation keys with the same values.
      You can safely roll back from 1.4 to 1.3, and things with init-containers
      will still work (pods, deployments, etc).

* Admit critical pods in the kubelet ([#38836](https://github.com/kubernetes/kubernetes/pull/38836), [@bprashanth](https://github.com/bprashanth))
* assign -998 as the oom_score_adj for critical pods (e.g. kube-proxy) ([#39114](https://github.com/kubernetes/kubernetes/pull/39114), [@dchen1107](https://github.com/dchen1107))

- There is now support for collecting pod logs under `/var/log/pods/NAMESPACE_NAME_UID` to stackdriver with `k8s_pod` resource type. ([#74502](https://github.com/kubernetes/kubernetes/pull/74502), [@Random-Liu](https://github.com/Random-Liu))

* **[Pod priority and preemption](https://kubernetes.io/docs/concepts/configuration/pod-priority-preemption/) is now enabled by default.** Note that this means that pods from *any* namespace can now request priority classes that compete with and/or cause preemption of critical system pods that are already running. If that is not desired, disable the PodPriority feature by setting `--feature-gat...