generate and measure CPU load with node.js

load-generator.js

#!/usr/bin/env node

require(__dirname+"/processor-usage.js").startWatching();

var shouldRun = true;
var desiredLoadFactor = .5;

function blockCpuFor(ms) {
	var now = new Date().getTime();
	var result = 0
	while(shouldRun) {
		result += Math.random() * Math.random();
		if (new Date().getTime() > now +ms)
			return;
	}	
}

function start() {
	shouldRun = true;
	blockCpuFor(1000*desiredLoadFactor);
	setTimeout(start, 1000* (1 - desiredLoadFactor));
}

setInterval(function() {
    console.log("current process cpu usage: "+(global.processCpuUsage || 0)+"%");}
, 1000);

if (process.argv[2]) {
    var value = parseFloat(process.argv[2]);
    if (value < 0 || value > 1) {
        console.log("please give desired load value as a range [0..1]");
	process.exit(-1);
    } else {
        desiredLoadFactor = value;
    }
}
start();

processor-usage.js

"use strict";
var fs = require('fs');

function ProcessUsageWatcher() {
    global.pubcrawler = global.pubcrawler || {};
    global.pubcrawler.processCpuUsage = 0;
}

ProcessUsageWatcher.prototype = {

    startWatching: function() {
        if (this.interval) {
            return;
        }

        var getUsage = function(cb){
            fs.readFile("/proc/" + process.pid + "/stat", function(err, data){
                var elems = data.toString().split(' ');
                var utime = parseInt(elems[13]);
                var stime = parseInt(elems[14]);

                cb(utime + stime);
            });
        };

        this.interval = setInterval(function(){
            getUsage(function(startTime){
                setTimeout(function(){
                    getUsage(function(endTime){
                        var delta = endTime - startTime;
                        var percentage = 100 * (delta / 500);
                        global.processCpuUsage = percentage;
                    });
                }, 5000);
            });
        }, 1000);
    },

    stopWatching : function()  {
        if (this.interval) {
            clearInterval(this.interval);
        }
    }
};

var instance = new ProcessUsageWatcher();
exports.startWatching = instance.startWatching;
exports.stopWatching = instance.stopWatching;

timer-blockout-example.js

#!/usr/bin/env node

require(__dirname+"/processor-usage.js").startWatching();

var shouldRun = true;

function blockCpu() {
	var result = 0;
	while(shouldRun) {
		result += Math.random() * Math.random();
	}	
	return result;
}

function start() {
	shouldRun = true;
	blockCpu();
	setTimeout(stop, 1000);
}

function stop() {
	console.log("Stopping cpu hog");
	shouldRun = false;
}

start();