static final class Helper<K, V>
        implements InternalEntryHelper<
            K, V, StrongKeyStrongValueEntry<K, V>, StrongKeyStrongValueSegment<K, V>> {
      private static final Helper<?, ?> INSTANCE = new Helper<>();

      @SuppressWarnings("unchecked")
      static <K, V> Helper<K, V> instance() {
        return (Helper<K, V>) INSTANCE;
      }

      @Override

- Added Coordinated Leader Election as Alpha under the `CoordinatedLeaderElection` feature gate. With the feature enabled, the control plane can use LeaseCandidate objects (coordination.k8s.io/v1alpha1 API group) to participate in a leader election and let the kube-apiserver select the best instance according to some strategy. ([#124012](https://github.com/kubernetes/kubernetes/pull/124012),...

- Client-go: Optimized leaders renewing leases by updating leader lock optimistically without getting the record from the API server first. Also, a new metric `leader_election_slowpath_total` was added to allow users to monitor how many leader elections are updated non-optimistically.

    static final class Helper<K, V>
        implements InternalEntryHelper<
            K, V, StrongKeyStrongValueEntry<K, V>, StrongKeyStrongValueSegment<K, V>> {
      private static final Helper<?, ?> INSTANCE = new Helper<>();

      @SuppressWarnings("unchecked")
      static <K, V> Helper<K, V> instance() {
        return (Helper<K, V>) INSTANCE;
      }

      @Override

### Other notable changes

- Fixed an issue where kubelet does not set case-insensitive headers for http probes. (#117182, @dddddai) ([#117333](https://github.com/kubernetes/kubernetes/pull/117333), [@dddddai](https://github.com/dddddai)) [SIG API Machinery, Apps and Node]

### Feature

- 'Container `preStop` and `postStart` lifecycle handlers using `httpGet` now
  honor the specified `scheme` and `headers` fields. This enables setting custom
  headers and changing the scheme to `HTTPS`, consistent with container
  startup/readiness/liveness probe capabilities. Lifecycle handlers configured

    public void clear() {
      ReferenceEntry<K, V> e = head.getNextInWriteQueue();
      while (e != head) {
        ReferenceEntry<K, V> next = e.getNextInWriteQueue();
        nullifyWriteOrder(e);
        e = next;
      }

      head.setNextInWriteQueue(head);
      head.setPreviousInWriteQueue(head);
    }

    @Override
    public Iterator<ReferenceEntry<K, V>> iterator() {

- Added `kubectl node drain` helper callbacks `OnPodDeletionOrEvictionStarted`
  and `OnPodDeletionOrEvictionFailed`; people extending `kubectl` can use these
  new callbacks for more granularity. Deprecated the `OnPodDeletedOrEvicted`

- The `NodeConfiguration` kind in the kubeadm v1alpha2 API has been renamed `JoinConfiguration` in v1alpha3...