NodeJS script running in cluster

cluster-script.js

const { spawn } = require("child_process");
const fs = require("fs");
const cluster = require("cluster");

const numCPUs = require("os").cpus().length;
const scriptFile = './script.sh';

let tasks = [];

function runScript(arg) {
  const script_process = spawn(scriptFile, [arg]);

  script_process.stdout.on("data", msg => {
    console.log(`[${process.env.TASK}]\t`, msg.toString());
  });

  script_process.stderr.on("data", error => {
    console.log(`[${process.env.TASK}]\t`, error.toString());
  });

  return script_process;
}

function getNextTask() {
  return tasks.shift();
}

if (cluster.isMaster) {
  // Fork workers.
  const initialWorkers = Math.min(numCPUs, tasks.length);
  for (let i = 0; i < initialWorkers; i++) {
    const task = getNextTask();
    cluster.fork({ TASK: task });
  }

  cluster.on("exit", (worker, code, signal) => {
    if (tasks.length > 0) {
      const task = getNextTask();
      cluster.fork({ TASK: task });
    }
  });
} else {
  const task = process.env.TASK;
  const task_process = runScript(task);

  task_process.on("exit", process.exit);
}