docs: function(app) {
    app.loadConfigBaseApp(Constants.RESERVED.SERVERS, path.join(app.get(Constants.RESERVED.SERVICE_PATH), Constants.FILEPATH.SERVER));
    let servers = app.get(Constants.RESERVED.SERVERS);
    let serverMap = {}, slist, i, l, server;
    for (let serverType in servers) {
      slist = servers[serverType];
      for (i = 0, l = slist.length; i < l; i++) {
        server = slist[i];
        server.serverType = serverType;
        if(server[Constants.RESERVED.CLUSTER_COUNT]) {
          utils.loadCluster(app, server, serverMap);
          continue;
        }
        serverMap[server.id] = server;
        if (server.wsPort) {
          logger.warn('wsPort is deprecated, use clientPort in frontend server instead, server: %j', server);
        }
      }
    }
    app.set(Constants.KEYWORDS.SERVER_MAP, serverMap);
  }