- Flag `--concurrent-node-syncs` has been added to cloud node controller which defines how many workers in parallel will be initialising and synchronising nodes. ([#113104](https://github.com/kubernetes/kubernetes/pull/113104), [@pawbana](https://github.com/pawbana)) [SIG API Machinery, Cloud Provider and Scalability]

- Authentication token cache size is increased (from 4k to 32k) to support clusters with many nodes or many namespaces with active service accounts. ([#83643](https://github.com/kubernetes/kubernetes/pull/83643), [@lavalamp](https://github.com/lavalamp))

- Added a new scheduler metric, `pod_scheduling_sli_duration_seconds`,...

<p>
A complete program is created by linking a single, unimported package
called the <i>main package</i> with all the packages it imports, transitively.
The main package must
have package name <code>main</code> and
declare a function <code>main</code> that takes no
arguments and returns no value.
</p>

<pre>
func main() { … }
</pre>

<p>

  Now, when unschedulable Pods are updated, the scheduling queue checks with QueueingHint(s) whether the update may make the pods schedulable, and requeues them to activeQ/backoffQ **only when** at least one QueueingHint(s) return Queue. 
  

- Revised `OpenAPI v2` fetching for CustomResourceDefinitions. CRDs are now aggregated lazily,
  which improves resource usage during installation of many CRDs. As a result, the first request
  to fetch the OpenAPI may be slower. ([#118808](https://github.com/kubernetes/kubernetes/pull/118808), [@Jefftree](https://github.com/Jefftree))

  // are cases when the state may be lost due to node restarts and then the value
  // may be reset to 0. The value is never negative.
  optional int32 restartCount = 5;

  // Image is the name of container image that the container is running.
  // The container image may not match the image used in the PodSpec,
  // as it may have been resolved by the runtime.

  - `--port`
  - `--address`
  The insecure port flags `--port` may only be set to 0 now.
- Kube-scheduler: the `--port` and `--address` flags have no effect and would be removed in v1.24.
  The insecure port flags `--port` may only be set to 0 now.

  If the `subPath` is a file rather than a directory, Pods may fail to start ([#45613](https://github.com/kubernetes/kubernetes/issues/45613)).

  **Do not upgrade to v1.6.3** if your cluster may run Pods with such subPaths.

## Downloads for v1.6.3


filename | sha256 hash
-------- | -----------

- Fixed a bug where init containers may fail to start due to a temporary container runtime failure. ([#127213](https://github.com/kubernetes/kubernetes/pull/127213), [@SergeyKanzhelev](https://github.com/SergeyKanzhelev)) [SIG Node]