class Redis::Cluster::Option

def add_common_node_option_if_needed(options, node_opts, key)

scheme, username, password and so on.
So we should complement additional information such as:
Redis cluster node returns only host and port information. 
def add_common_node_option_if_needed(options, node_opts, key)
  return options if options[key].nil? && node_opts.first[key].nil?
  options[key] ||= node_opts.first[key]
end