src/config/setup.js

// Import the neccesary modules.
import bodyParser from 'body-parser';
import compress from 'compression';
import mongoose from 'mongoose';
import passport from 'passport';
import responseTime from 'response-time';

import { createExpressWinston } from './logger';
import {
  dbHosts,
  dbName,
  Promise
} from './constants';

/**
 * Connection and configuration of the MongoDB database.
 * @returns {void}
 */
function _connectMongoDB() {
  mongoose.Promise = Promise;
  mongoose.connect(`mongodb://${dbHosts.join(',')}/${dbName}`, {
    db: {
      native_parser: true // eslint-disable-line camelcase
    },
    replset: {
      rs_name: 'br0',  // eslint-disable-line camelcase
      connectWithNoPrimary: true,
      readPreference: 'nearest',
      strategy: 'ping',
      socketOptions: {
        keepAlive: 1
      }
    },
    server: {
      readPreference: 'nearest',
      strategy: 'ping',
      socketOptions: {
        keepAlive: 1
      }
    }
  });
}

/**
 * Setup the Express service.
 * @param {Express} app - The ExpresssJS instance.
 * @param {?Boolean} [pretty] - Pretty output with Winston logging.
 * @param {?Boolean} [verbose] - Debug mode for no output.
 * @returns {void}
 */
export default function doSetup(app, pretty, verbose) {
  // Used to extract data from query strings.
  RegExp.escape = text => text.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, '\\$&');

  // Connection and configuration of the MongoDB database.
  _connectMongoDB();

  // Enable parsing URL encoded bodies.
  app.use(bodyParser.urlencoded({
    extended: true
  }));

  // Enable parsing JSON bodies.
  app.use(bodyParser.json());

  // Enables compression of response bodies.
  app.use(compress({
    threshold: 1400,
    level: 4,
    memLevel: 3
  }));

  // Enable response time tracking for HTTP request.
  app.use(responseTime());

  // Enable HTTP request logging.
  if (pretty && !verbose) app.use(createExpressWinston());

  // Enable Passport authentication.
  app.use(passport.initialize());
}