const cluster = require('cluster');

let workers = [];
/**
* @module A module for creating and managing multiple workflows (worker) in Node.js.
*/
module.exports = () => {
  // to read number of cores on system
  let numCores = require('os').cpus().length;
  console.log('Master cluster setting up ' + numCores + ' workers');

  // iterate on number of cores need to be utilized by an application
  // current example will utilize all of them
  for(let i = 0; i < numCores; i++) {
    // creating workers and pushing reference in an array
    // these references can be used to receive messages from workers
    workers.push(cluster.fork());

    // to receive messages from worker process
    workers[i].on('message', function(message) {
      console.log(message);
    });
  }

  // process is clustered on a core and process id is assigned
  cluster.on('online', function(worker) {
    console.log('Worker ' + worker.process.pid + ' is listening');
  });

  // if any of the worker process dies then start a new one by simply forking another one
  cluster.on('exit', function(worker, code, signal) {
    console.log('Worker ' + worker.process.pid + ' died with code: ' + code + ', and signal: ' + signal);
    console.log('Starting a new worker');
    cluster.fork();
    workers.push(cluster.fork());
    // to receive messages from worker process
    workers[workers.length-1].on('message', function(message) {
      console.log(message);
    });
  });
};