WebSocket exec/attach/portforward requests directly to the kubelet rather than translating or tunneling them at the API server. The kubelet now handles WebSocket-to-SPDY stream translation (exec/attach) and WebSocket tunneling (portforward) using the same handlers previously used at the API server. The kubelet advertises support for this feature to the API server via the NodeDeclaredFeatures mechanism; the API server only proxies directly to a kubelet that has advertised support. Two new ALPHA metrics are...

- ACTION REQUIRED:
  

- New configuration is introduced to the kubelet that allows it to track container images and the list of authentication information that leads to their successful pulls. This data is persisted across reboots of the host and restarts of the kubelet.
  

    1. Generate a `/var/lib/kubelet/instance-config.yaml` file to customize the `containerRuntimeEndpoint` field in per-node kubelet configurations.
    2. Remove the `kubeadm.alpha.kubernetes.io/cri-socket` annotation from nodes during upgrade operations.