js version of toobusy

tooslow.js

var interval = 500
var maxLag = 70
var lag = 0
var decay = 3
var mark = []
var timer = null

function tooslow() {
	return (lag > maxLag) &&
		Math.random() < ((lag - maxLag) / maxLag)
}

tooslow.lag = function () { return lag }

tooslow.maxLag = function (x) {
	if (x > 9) {
		maxLag = x
	}
	return maxLag
}

tooslow.shutdown = function () {
	clearTimeout(timer)
}

function ping() {
	mark = process.hrtime()
	setImmediate(pong)
}

function pong() {
	var delta = process.hrtime(mark)
	var delay = (delta[0] * 1e9 + delta[1]) / 1e6
	lag = Math.floor(
		(delay + (lag * (decay - 1))) / decay
	)
	timer = setTimeout(ping, interval)
}

ping()

module.exports = tooslow