A simple processor-sharing queue simulator in node.js

ps_queue_sim.js

var PoissonProcess = require('poisson-process');
var sleep = require('sleep');
var http = require('http');
var port = process.env.PORT || 1337;
var TIMESLICE_MILLIS = 1;
var MEAN_SLEEP_MILLIS = 500;

function sleep_for_timeslice(total_ms, ms_left, req_timestamp, res) {
    if (ms_left > 0) {
        sleep.usleep(TIMESLICE_MILLIS*1000);
        setTimeout(sleep_for_timeslice, TIMESLICE_MILLIS, total_ms, ms_left-TIMESLICE_MILLIS, req_timestamp, res);
    } else {
        var cur_timestamp = (new Date).getTime();
        res.writeHead(200, { 'Content-Type': 'text/html' });
        res.end('slept for ' + total_ms + 'ms out of total ' + (cur_timestamp-req_timestamp) + 'ms\n');
    }
}

http.createServer(function (req, res) {
    // sleep for exponentially distributed time in milliseconds
    var sleep_millis = Math.round(PoissonProcess.sample(MEAN_SLEEP_MILLIS));
    var req_timestamp = (new Date).getTime();
    sleep_for_timeslice(sleep_millis, sleep_millis, req_timestamp, res);
}).listen(port);

console.log('Server running on port %s', port);