def all_nodes
      collection = connection[nodes_collection]
      collection.find.batch_size(999).projection(_id: 1).map { |k| k[:_id] }
    end
def all_nodes
      collection = connection[nodes_collection]
      collection.find.batch_size(999).projection(_id: 1).map { |k| k[:_id] }
    end
get all node names