### SIG CLI

SIG CLI's main focus this release was on refactoring `kubectl` internals to improve composability, readability and testability of `kubectl` commands. Those refactors will allow the team to extract a mechanism for extensibility of kubectl -- that is, plugins -- in the next releases.

### SIG Cluster Lifecycle

Compression happens inflight, i.e objects are compressed before being written to disk(s).
MinIO uses [`klauspost/compress/s2`](https://github.com/klauspost/compress/tree/master/s2)
streaming compression due to its stability and performance.

This algorithm is specifically optimized for machine generated content.
Write throughput is typically at least 500MB/s per CPU core,
and scales with the number of available CPU cores.

- kube-proxy metrics are now marked as with the ALPHA stability level. ([#81626](https://github.com/kubernetes/kubernetes/pull/81626), [@logicalhan](https://github.com/logicalhan))

- Change `pod_preemption_victims` metric from Gauge to Histogram. ([#83603](https://github.com/kubernetes/kubernetes/pull/83603), [@Tabrizian](https://github.com/Tabrizian))
- Following metrics from kubelet are now marked as with the ALPHA stability level:

    - [CustomResourceDefinition Defaulting](#customresourcedefinition-defaulting)
    - [CustomResourceDefinition OpenAPI Publishing](#customresourcedefinition-openapi-publishing)
  - [Cluster Lifecycle Stability and Usability Improvements](#cluster-lifecycle-stability-and-usability-improvements)
  - [Continued improvement of CSI](#continued-improvement-of-csi)
    - [Additional Notable Feature Updates](#additional-notable-feature-updates)

          (o1, o2) ->
              ComparisonChain.start()
                  .compare(o1.iterator.peek(), o2.iterator.peek(), itemComparator)
                  // When elements are equal, use insertion order to maintain stability
                  .compare(o1.index, o2.index)
                  .result();

      queue = new PriorityQueue<>(2, heapComparator);

      int index = 0;

- Kube-apiserver: fixes a 1.27+ regression in watch stability by serving watch requests without a resourceVersion from the watch cache by default, as in <1.27 (disabling the change in #115096 by default). This mitigates the impact of an etcd watch bug (https://github.com/etcd-io/etcd/pull/17555). If the 1.27 change in #115096 to serve these requests from underlying storage is still desired despite the impact on watch stability, it can be re-enabled with a `WatchFromStorageWithoutResourceVersion`...

     * empty at any point. (The sum ensures accuracy up through at least 1<<31 per-segment
     * modifications before recheck.)  Method containsValue() uses similar constructions for
     * stability checks.
     */
    long sum = 0L;
    Segment<K, V, E, S>[] segments = this.segments;
    for (int i = 0; i < segments.length; ++i) {
      if (segments[i].count != 0) {
        return false;
      }

  * **beta** PodSecurityPolicy objects limits use of security-sensitive features by pods.
* Kubectl
  * Display line number on JSON errors
  * Add flag -t as shorthand for --tty
* Resources
  * Improved node stability by *optionally* evicting pods upon memory pressure - [Design Doc](https://github.com/kubernetes/kubernetes/blob/release-1.3/docs/proposals/kubelet-eviction.md)

### Bug or Regression

- Fixed a bug where a high churn of events was causing master instability by reducing the maximum number of objects (events) attached to a single etcd lease. ([#100452](https://github.com/kubernetes/kubernetes/pull/100452), [@mborsz](https://github.com/mborsz)) [SIG API Machinery and Instrumentation]