Best Practice of Connecting MongoDB Using Mongoose ODM

app.js

var mongoose = require('mongoose');
var express = require('express');

// Connect to MongoDB Using Mongoose ODM
mongoose.connect('mongodb://localhost:27017/integration_test', { useNewUrlParser: true });

// Listen For Mongoose Connection Error
mongoose.connection.on("error", function (err) { console.error('Failed to Connect MongoDB'); });

// Listen For Mongoose Disconnection
mongoose.connection.on('disconnected', function () { console.log('MongoDB Disconnected'); });

// Listen For Mongoose Connection
mongoose.connection.on("connected", function () {

  console.log("MongoDB Connected");

  // Express.js HTTP Server
  var app = express();
  port = process.env.port || 3000;
  ip = process.env.ip;
  app.listen(port, ip, function () {
    console.log('listening on port ' + port);
  });

});

var onTerminate = function () {
  mongoose.connection.close(function () {
    console.log('Close MongoDB Connection');
    process.exit(0);
  });
}

// Fire the Event On Application Stop/Termination
process.on('SIGINT', onTerminate).on('SIGTERM', onTerminate);