Use cluster for master/child process communication

cluster.js

const cluster = require('cluster');
const app = require('express')();
const bodyParser = require('body-parser');

const cpus = 4;

var index = 0;

//next();

if(cluster.isMaster) 
{

	console.log(`Master ${process.id} is running`);

	//Fork workers
	for(let i=1; i<=cpus; i++)
	{

		cluster.fork();

	}


	/** create new worker after a worker is killed*/
	cluster.on('exit', (worker, code, signal)=>{

		console.log(`Worker ${worker.process.pid} died`);
		console.log('creating new worker process');
		cluster.fork();

	});

	cluster.on('message', (worker, message) =>{

		console.log(`Received a message from ${worker.process.pid} : ${message}`);

	})


} else

{
	var pid = process.pid;

	const jsonParser =bodyParser.json();

	app.get('/', (req, res)=>res.send(`worker process id is ${pid}`));

	app.get('/kill', (req,res)=>{

		res.send(`Now killing worker: ${pid}`);
		process.exit(1);

	});


	app.post('/send',jsonParser, (req, res)=>{

		var msg = JSON.stringify(req.body);

			res.send(`send message ${msg} to master`);
			process.send(msg);

		}
		);

	app.listen(3000, () => console.log(`worker#${pid} now listening on port 3000`));

}