index.js

/**
 * Run the server and cluster. Main entry point
 */

'use strict';

// built-in node modules
const os = require('os');

// third-party node modules
const throng = require('throng'); // concurrency

// env variables
const NODE_ENV = process.env.NODE_ENV || 'development';
const PORT = process.env.PORT ? Number(process.env.PORT) : 8000;
const PROCESSES = NODE_ENV === 'production' ? process.env.WEB_CONCURRENCY || os.cpus().length : 1; // number of cores

// function to start app
async function startApp(processId) {
  const models = require('./models'); // get models
  const { gracefulExit } = require('./middleware/exit'); // exit

  // create server
  const server = require('./server'); // get app

  // Print Process Info
  console.log(`WEB process.pid: ${process.pid}`);
  console.log(`WEB process.env.NODE_ENV: ${NODE_ENV}`);

  // to check if database connection is established
  await models.db.authenticate().catch(err => {
    console.error(err);
    process.exit(1);
  });

  // listen server
  server.listen(PORT, () => {
    console.log(`Process ID: ${processId} - Server started on port ${PORT}`);

    // On terminate command: killall node or process.kill(process.pid)
    process.on('SIGTERM', () => {
      console.log(`Process ${processId} exiting...`);

      // gracefully exit server
      gracefulExit(server);
    });
  });
}

// run concurrent workers
// throng({
//   workers: PROCESSES, // Number of workers (cpu count)
//   lifetime: Infinity, // ms to keep cluster alive (Infinity)
//   grace: 5000 // ms grace period after worker SIGTERM (5000)
// }, startApp);
throng({
  worker: startApp,
  count: PROCESSES, // Number of workers (cpu count)
  lifetime: Infinity, // ms to keep cluster alive (Infinity)
  grace: 5000 // ms grace period after worker SIGTERM (5000)
});