child_process.js

// parent.js

const fork = require('child_process').fork;
const CHILDREN = require('os').cpus().length;

const pool = [];
const OPTS = {
  stdio: [0, 1, 2, 'ipc']
};

console.log(`Parent running with pid ${process.pid}`);

for (let child_id = 0; child_id < CHILDREN; child_id++) {
  const child = fork('./child.js', [String(child_id)], OPTS);
  pool.push(child);
  child.on('message', message => {
    // console.log('MESSAGE', child_id, message);
  });
}

// Send 1M messages
const getWorker = roundRobin();
for (let i = 0; i < 1000000; i++) {
  const child = getWorker();
  child.send({doWork: i});
  if (i % 1000 === 0) {
    console.log(`${i}/1000000`);
  }
}

function roundRobin() {
  let pointer = -1;
  return function() {
    pointer++;
    if (pointer >= pool.length) {
      pointer = 0;
    }

    return pool[pointer];
  }
}


// child.js

if (!process.send) {
  throw new Error("Must be run as a child process!");
}

const child_id = process.argv[2];

console.log(`Child ${child_id} running with pid ${process.pid}`);
// console.log('ENV', child_id, JSON.stringify(process.env));

process.on('message', message => {
  // console.log('CHILD MESSAGE', child_id, message);
  const data = Math.sqrt(message.doWork);
  process.send({
    work: 'done',
    data,
    worker: child_id,
    input: message.doWork
  });
});

/*
setTimeout(() => {
  process.send(`Hello sent to parent from child ${child_id}`);
  process.exit();
}, Math.random() * 5000 + 5000); // Between 5s and 10s
*/