app.js

/**
 * Main application file:
 */

// Info about current and allowed environments.
const environments = require('#configs/envinorments');
// Middleware for parsing requests bodies.
const bodyParser = require('body-parser');
// Express.
const express = require('express');
const http = require('http');
// Mild security.
const helmet = require('helmet');
// Cross-origin requests middleware.
const cors = require('cors');

// Server configuration:
// ORM.
const DB = require('#services/db.service');
// Port info.
const serverConfig = require('#configs/server');
// Server configuration\

// Express application.
const app = express();
// HTTP server (Do not use HTTPS, manage TLS with some proxy, like Nginx).
const server = http.Server(app);
// Routes.
const routes = require('#routes/');


// Allow cross origin requests
// (configure to only allow requests from certain origins).
app.use(cors());

// Set views path.
app.set('views', __dirname+'/views');
// Set template engine (Pug by default).
app.set('view engine', 'pug');
// Set folder for static contents.
app.use(express.static('public'));

// Secure express app.
app.use(helmet({
	dnsPrefetchControl: false,
	frameguard: false,
	ieNoOpen: false,
}));

// Parsing the request bodies.
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

// Setup routes.
app.use(routes({ app }));


// Reference to the active database connection.
let db;
// Initialize server:
(async function() {
	if (environments.allowed.indexOf(environments.current) === -1) {
		console.error(`NODE_ENV is set to ${environments.current}, but only ${environments.allowed.toString()} are valid.`);
		process.exit(1);
	}

	// Start ORM.
	db = await DB.service(environments.current).start();
})()
.then(()=>{
	server.listen(serverConfig.port, ()=>{
		// Server is up!
		console.info(`Server is running on port: ${serverConfig.port}`);
		return db;
	});
});
// Initialize server\

function _gracefulShutdown(exit=false) {
	console.warn('Received SIGINT or SIGTERM. Shutting down gracefully...');
	const exitCode = exit ? 1 : 0;

	server.close(() => {
		console.info('Closed out remaining connections.');
		process.exit(exitCode);
	});

	// Force stop after 5 seconds:
	setTimeout(() => {
		console.error('Could not close connections in time, forcefully shutting down');
		process.exit(exitCode);
	}, 5*1000);
}

process.on('unhandledRejection', (reason, p) => {
	console.error(reason, 'Unhandled Rejection at Promise', p);
});
	
process.on('uncaughtException', err => {
	console.error(err, 'Uncaught Exception thrown');
	
	_gracefulShutdown(true);
});