scalable express 4 cluster with (worker)bus

_design.gif

app.js

/*
 * api-server which uses multiple cpucores:
 *
 *   cpu #1      : for webrequests (express)
 *   cpu #2..999 : for workers (receive webhook from trello, push to gmail e.g.)
 *
 */
const cluster = require('cluster');
const numCPUs = require('os').cpus().length;  
var port      = parseInt(process.env.PORT) || 3002
var host      = process.env.HOST           || '127.0.0.1'
var simplebus = require('simplebus')

var workers   = ['url2pdf','pdf2html']

var startserver = () => {    
    // Create bus server (for workers)
    var bus       = simplebus.createBus(1000)     
    var server    = simplebus.createServer(bus, port+1, host)
    server.start()

    // Create a new Express application.
    var express = require('express')
    var app = express()      
    var bodyParser = require('body-parser')

    app.use( bodyParser.json() )    
    app.use( function(req, res, next){
        if( req.method != "get" && !req.url.match(/\/(swagger-ui|console|favico|openapi)/) )
            console.log( req.method.toUpperCase()+' '+req.url+' {'+ Object.keys(req.body).join(',') +'}' )
        bus.post({ 
            type: "http", 
            method: req.method,             
            body: req.body, 
            url: req.url, 
            header:req.header 
        })
        if( req.url.match(/\/worker\//) ) return res.send({error:false, msg:"message queued for delivery"}).end()
        next()    
    })

    app.listen(port, function(){    
      console.log("express listening on "+host+':'+port)
      console.log("bus     listening on "+host+':'+(port+1))
    })

  // Fork workers.
  for (let i = 0; i < numCPUs; i++) cluster.fork(); 
  cluster.on('exit', (worker, code, signal) => {
    console.log(`worker ${worker.process.pid} died`);
  });
}

var startworker = () => {
    process.config = config
    var bus     = simplebus.createClient(port+1, host)
    bus.start( () => {
        
        bus.subscribe({type:'http'}, () => {
          // doAnalytics()
        })
    
        workers.forEach( (worker, i) => {
            console.log( `worker ${process.pid} <= /worker/${worker}` )
            bus.subscribe( {type:'http', url: `/worker/${worker}`}, function (worker,msg) {