server.js

import dotenv from 'dotenv';
dotenv.config({ path: './config.env' });

// Unhandled Exception (a bug in the code)
process.on('uncaughtException', (err) => {
  console.log('UNCAUGHT EXCEPTION! 💥 Shutting down...');
  console.log(err.name, err.message);
  process.exit(1);
});
import app from './app.js';
import mongoose from 'mongoose';

// Database connection
const DB = process.env.DATABASE.replace(
  '<PASSWORD>',
  process.env.DATABASE_PASSWORD
);
mongoose
  .connect(DB, {
    serverSelectionTimeoutMS: 30000,
    socketTimeoutMS: 45000,
  })
  .then(() => {
    console.log('DB connection successful');
  });

// Listen to the port
const PORT = process.env.PORT || 3000;
const server = app.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}`);
});

// Unhandled Promise Rejection (a promise that is rejected but not caught like mongoDB connection)
process.on('unhandledRejection', (err) => {
  console.log('UNHANDLED REJECTION! 💥 Shutting down...');
  console.log(err.name, err.message);
  // close the server first to avoid the request and responses that are running in the background to be terminated and after that exit the application by 1 means exit with failure
  server.close(() => {
    process.exit(1);
  });
});

// A signal that sent to the process to tell it to terminate gracefully in production by vercel, heroku, ...etc.
process.on('SIGTERM', () => {
  console.log('👋 SIGTERM RECEIVED. Shutting down gracefully');
  server.close(() => {
    console.log('💥 Process terminated!');
  });
});