Breaking change wishlists.
See code changes and v4.0 upgrade guide for any breaking changes.
/health endpoint output.
{"health":"true"}.{"health":true}.kubectl get componentstatuses command.etcd --proxy* flags; no more v2 proxy.etcdctl backup command.clientv3.Client.KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error) is now clientv4.Client.KeepAlive(ctx context.Context, id LeaseID) <-chan *LeaseKeepAliveResponse.
Watch, KeepAlive does not return errors.KeepAlive call.github.com/coreos/client to github.com/coreos/clientv2.