old_contents: var mongoose = require('mongoose');
  var config = require('../config').config;
  mongoose.connect(config.db, function (err) {
    if (err) {
      console.error('connect to %s error: ', config.db, err.message);
      process.exit(1);
    }
  });
  
  // models
  require('./user');
  require('./article');
  
  exports.User = mongoose.model('User');
  exports.Article = mongoose.model('Article');
new_contents: var mongoose = require('mongoose');
  var config = require('../config').config;
  
  // models
  require('./user');
  require('./article');
  mongoose.connect(config.db, function (err) {
  if (err) {
          mongoose.connection.close();
          console.error('connect to %s error: ', config.db, err.message);
          process.exit(1);
      }
  });
  exports.User = mongoose.model('User');
  exports.Article = mongoose.model('Article');
subject: update db