Application(Webinterface + Cron-Jobs + HTTP-Clients) -- JAVA vs NODEJS - node.js

Question

iam programming a prototype application with the following components:
webinterface for admins
doing cron jobs(statistic generation, ..)
interact with other webservices over http
I started programming with nodejs(typescript) and i got the connection to the other services. Now i got a problem with cron-jobs in nodejs.
Iam using node-cron for executing the cronjob.
Inside one job i need to obtain the status of much pc's and make a summary of it. If i would do this, this would block the main thread.
So i think I need to this in a separate thread.
How can i do this in nodejs? Should i use webworker-threads?
Am I on the proper way?
Should i better use Java(Grails/Spring) for this?
I really like the simplicity of nodejs (for http clients, ..)
Hope someone can give me hope that iam on the proper way.

Answer 1

I will just use Node Cluster. Using cluster, a master can create a multiple workers, which means your cron wont block incoming request. Just make sure that only 1 worker doing the Cron.
I have never working with node-cron before, but I have experience with the SyncedCron. But should be the same.
For the http client there are a lot libraries doing this, you can check Request or httpclient.
Your code should look something like this :
var cluster = require('cluster');
var http = require('http');
var numWorkers = require('os').cpus().length-1; // just give 1 cpu for OS to use, or maybe 2
if (cluster.isMaster) {
console.log('Master cluster setting up ' + numWorkers + ' workers...');
var cronPID=null;
for(var i = 0; i < numWorkers; i++) {
var worker=cluster.fork();
if(i==0){
//instructing the first worker to assume role of SyncedCron.
worker.send('you do it!');
cronPID=worker.process.pid;
console.log("worker "+cronPID+" choosed as Cron worker!");
}
}
cluster.on('online', function(worker) {
console.log('Worker ' + worker.process.pid + ' is online');
});
cluster.on('exit', function(worker, code, signal) {
// have to revive the worker
console.log('Worker ' + worker.process.pid + ' died with code: ' + code + ', and signal: ' + signal);
console.log('Starting a new worker');
var newWorker=cluster.fork();
if(cronPID==worker.process.pid)
{ // need to re-elect a new cron worker!
newWorker.send('you do it!');
cronPID=newWorker.process.pid;
console.log("worker "+cronPID+" choosed as Cron worker!");
}
});
}else
{ // worker sides
process.on('message', (msg) => {
// validate your message that you get
// if validated, create a cron job here
});
// create your express below, I assume you use express instead of node's http library
var express = require('express');
var app = express();
app.post...........
}
Note :
To revive the master, use something like "forever"
Your server should have multiple core, at least 4 but I recommend more (8 maybe?).