class ApplicationApiImpl implements ApplicationApi {

    @Override
    public List<StorageNode> getUpStorageNodesInGroupInClusterOrder() {
        return clusterInOrder.stream()
                .map(ClusterApi::upStorageNodeInGroup)
                .filter(Optional::isPresent)
                .map(Optional::get)
                .collect(Collectors.toList());
    }

    public  ApplicationApiImpl(NodeGroup nodeGroup,
                              ApplicationLock lock,
                              ClusterControllerClientFactory clusterControllerClientFactory,
                              int numberOfConfigServers, Clock clock);

}