NodeJS Run multiple processes from simple functions

node-workload-runner-example.js

const cluster = require('cluster');

/**
 * @param {Function[]} workloads - simple paramaterless functions
 * @param {{ restartOnExit: bool? }} opts
 */
function runWorkloads(workloads, opts) {

    const restartOnExit = opts?.restartOnExit ?? false;
    const workloadLookup = Object.fromEntries(
        Array.from(new Set(workloads))
            .map(fn => [fn.name, fn])
    );
    
    if (cluster.isPrimary) {
        console.log(`Enter from primary`);
        workloads.map(fn => fn.name).forEach(workloadName => {
            const worker = startWorker(workloadName);
        });
    } else {
        process.on('message', msg => {
            const workloadName = msg;
            const workloadFn = workloadLookup[msg]; // function name sent
            
            logStartedWork(workloadName)
            workloadFn();
        })
    }
    
    function startWorker(workloadName) {
        /**
         * @type {cluster.Worker} worker
         */
         const worker = cluster.fork();
         console.log(`Forked. workload: ${workloadName}`);
         worker.send(workloadName);
         
         if (restartOnExit) worker.on('exit', () => startWorker(workloadName));
         return worker;
    }
    
    function logStartedWork(workloadName){
        console.log(`Worker process id ${cluster.worker.id} starting workload (${workloadName})..`);
    }
}

// work function exampless
function countTo10Slow(){
    let i = 1;
    const interval = setInterval(() => {
        if (i >= 10) clearInterval(interval);
        console.log(i++);
    }, 1000);
}

function throwAfter5Sec(){
    setTimeout(()=> {throw `Worker ${cluster.worker.id} threw..`}, 5000);
}

// define and run our workloads (simple paramaterless functions, can repeat same workload more than once)
const workloads = [
    countTo10Slow,
    throwAfter5Sec,
    countTo10Slow
];
runWorkloads(workloads, {restartOnExit: true}); // restartOnExit is useful for restarting if any exceptions occured