code: @Nullable
    public static List<String> readNodeList(String fileName) {
      String confDir = ServerConfiguration.get(PropertyKey.CONF_DIR);
      List<String> lines;
      try {
        lines = Files.readAllLines(Paths.get(confDir, fileName), StandardCharsets.UTF_8);
      } catch (IOException e) {
        System.err.format("Failed to read file %s/%s.%n", confDir, fileName);
        return null;
      }
  
      List<String> nodes = new ArrayList<>();
      for (String line : lines) {
        String node = line.trim();
        if (node.startsWith("#") || node.length() == 0) {
          continue;
        }
        nodes.add(node);
      }
  
      return nodes;
    }
docs: Reads a list of nodes from given file name ignoring comments and empty lines.
  Can be used to read conf/workers or conf/masters.
  @param fileName name of a file that contains the list of the nodes
  @return list of the node names, null when file fails to read