app.js

#!/usr/bin/env node
/* eslint no-console: ["error", { allow: ["log", "error"] }] */

const cluster = require('cluster');
const config = require('./app/models/config-model');
const numCPUs = require('os').cpus().length;

const numProcesses = Math.min(config.server['max processes'], numCPUs);

if (cluster.isMaster) {
    // Fork workers.
    for (let i = 0; i < numProcesses; i++) {
        cluster.fork();
    }

    cluster.on('exit', (worker) => {
        console.log(
            `Worker ${worker.process.pid} sadly passed away. It will be reincarnated.`
        );
        cluster.fork();
    });
} else {
    const app = require('./config/express');
    const server = app.listen(app.get('port'), () => {
        const worker = cluster.worker ? cluster.worker.id : 'Master';
        const msg = `Worker ${worker} ready for duty at port ${
            server.address().port
        }! (environment: ${app.get('env')})`;
        console.log(msg);
    });
    /**
     * The goal of this timeout is to time out AFTER the client (browser request) times out.
     * This avoids nasty issues where a proxied submission is still ongoing but Enketo
     * drops the connection, potentially resulting in the browser queue not emptying,
     * despite submitting successfully.
     *
     * https://github.com/kobotoolbox/enketo-express/issues/564
     */
    server.timeout = app.get('timeout') + 1000;
}