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boomerang.js
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boomerang.js
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/**
\file boomerang.js
boomerang measures various performance characteristics of your user's browsing
experience and beacons it back to your server.
\details
To use this you'll need a web site, lots of users and the ability to do
something with the data you collect. How you collect the data is up to
you, but we have a few ideas.
Copyright (c) 2010 Yahoo! Inc. All rights reserved.
Code licensed under the BSD License. See the file LICENSE.txt
for the full license text.
*/
// beaconing section
// the parameter is the window
(function(w) {
var impl, boomr, k, d=w.document;
// Short namespace because I don't want to keep typing BOOMERANG
if(typeof BOOMR === "undefined") {
BOOMR = {};
}
// don't allow this code to be included twice
if(BOOMR.version) {
return;
}
BOOMR.version = "0.9";
// impl is a private object not reachable from outside the BOOMR object
// users can set properties by passing in to the init() method
impl = {
// properties
beacon_url: "",
// strip out everything except last two parts of hostname.
// This doesn't work well for domains that end with a country tld,
// but we allow the developer to override site_domain for that.
site_domain: w.location.hostname.
replace(/.*?([^.]+\.[^.]+)\.?$/, '$1').
toLowerCase(),
//! User's ip address determined on the server. Used for the BA cookie
user_ip: '',
// Ratio, used for the percentage-users tracking. Set ratio to the numeric percentage you want
// tracked, 0-100, with 100 being full tracking. No % sign.
ratio: '',
ratiocookiename: 'boomrsession',
events: {
"page_ready": [],
"page_unload": [],
"before_beacon": []
},
vars: {},
disabled_plugins: {},
fireEvent: function(e_name, data) {
var i, h, e;
if(!this.events.hasOwnProperty(e_name)) {
return false;
}
e = this.events[e_name];
for(i=0; i<e.length; i++) {
h = e[i];
h[0].call(h[2], data, h[1]);
}
return true;
},
addListener: function(el, sType, fn, capture) {
if(el.addEventListener) {
el.addEventListener(sType, fn, (capture));
}
else if(el.attachEvent) {
el.attachEvent("on" + sType, fn);
}
}
};
// We create a boomr object and then copy all its properties to BOOMR so that
// we don't overwrite anything additional that was added to BOOMR before this
// was called... for example, a plugin.
boomr = {
// Utility functions
utils: {
getCookie: function(name) {
if(!name) {
return null;
}
name = ' ' + name + '=';
var i, cookies;
cookies = ' ' + d.cookie + ';';
if ( (i=cookies.indexOf(name)) >= 0 ) {
i += name.length;
cookies = cookies.substring(i, cookies.indexOf(';', i));
return cookies;
}
return null;
},
setCookie: function(name, subcookies, max_age, path, domain, sec) {
var value = "",
k, nameval, c,
exp = "";
if(!name) {
return false;
}
for(k in subcookies) {
if(subcookies.hasOwnProperty(k)) {
value += '&' + encodeURIComponent(k)
+ '=' + encodeURIComponent(subcookies[k]);
}
}
value = value.replace(/^&/, '');
if(max_age) {
exp = new Date();
exp.setTime(exp.getTime() + max_age*1000);
exp = exp.toGMTString();
}
nameval = name + '=' + value;
c = nameval +
((max_age) ? "; expires=" + exp : "" ) +
((path) ? "; path=" + path : "") +
((typeof domain !== "undefined") ? "; domain="
+ (domain !== null ? domain : impl.site_domain ) : "") +
((sec) ? "; secure" : "");
if ( nameval.length < 4000 ) {
d.cookie = c;
// confirm cookie was set (could be blocked by user's settings, etc.)
return ( value === this.getCookie(name) );
}
return false;
},
getSubCookies: function(cookie) {
var cookies_a,
i, l, kv,
cookies={};
if(!cookie) {
return null;
}
cookies_a = cookie.split('&');
if(cookies_a.length === 0) {
return null;
}
for(i=0, l=cookies_a.length; i<l; i++) {
kv = cookies_a[i].split('=');
kv.push(""); // just in case there's no value
cookies[decodeURIComponent(kv[0])] = decodeURIComponent(kv[1]);
}
return cookies;
},
removeCookie: function(name) {
return this.setCookie(name, {}, 0, "/", null);
},
pluginConfig: function(o, config, plugin_name, properties) {
var i, props=0;
if(!config || !config[plugin_name]) {
return false;
}
for(i=0; i<properties.length; i++) {
if(typeof config[plugin_name][properties[i]] !== "undefined") {
o[properties[i]] = config[plugin_name][properties[i]];
props++;
}
}
return (props>0);
}
},
init: function(config) {
var i, k,
properties = ["beacon_url", "site_domain", "user_ip","ratio","ratiocookiename"];
if(!config) {
config = {};
}
for(i=0; i<properties.length; i++) {
if(typeof config[properties[i]] !== "undefined") {
impl[properties[i]] = config[properties[i]];
}
}
if(typeof config.log !== "undefined") {
this.log = config.log;
}
if(!this.log) {
this.log = function(m,l,s) { };
}
//check if ratio has been set
if(impl.ratio != ''){
var tc=BOOMR.utils.getSubCookies(BOOMR.utils.getCookie(impl.ratiocookiename));
// if boomr run is true then run boomerang during their session
// and skip calculating the ratio this time
if(tc != null && tc.run == "true"){
var runRatio = false;
// if boomr don't run session is false then don't run run boomerang during their session
// and just return
}else if(tc != null && tc.run == "false"){
return false;
}else{
//If ratio is set and no session cookie exists then roll the dice
var runRatio = true;
}
if(runRatio){
if(!this.randomNess()){
// set don't run boomerang session subcookie
BOOMR.utils.setCookie(
impl.ratiocookiename,
{run: "false"},
0,
"/",
null);
return false;
}else{
// set run boomerang session subcookie
BOOMR.utils.setCookie(
impl.ratiocookiename,
{run: "true"},
0,
"/",
null);
}
}
}
for(k in this.plugins) {
// config[pugin].enabled has been set to false
if( config[k]
&& typeof config[k].enabled !== "undefined"
&& config[k].enabled === false
) {
impl.disabled_plugins[k] = 1;
continue;
}
else if(impl.disabled_plugins[k]) {
delete impl.disabled_plugins[k];
}
// plugin exists and has an init method
if(this.plugins.hasOwnProperty(k)
&& typeof this.plugins[k].init === "function"
) {
this.plugins[k].init(config);
}
}
// The developer can override onload by setting autorun to false
if(typeof config.autorun === "undefined" || config.autorun !== false) {
impl.addListener(w, "load",
function() {
impl.fireEvent("page_ready");
}
);
}
// This must be the last one to fire
impl.addListener(w, "unload", function() { w=null; });
return this;
},
// The page dev calls this method when they determine the page is usable.
// Only call this if autorun is explicitly set to false
page_ready: function() {
impl.fireEvent("page_ready");
return this;
},
subscribe: function(e_name, fn, cb_data, cb_scope) {
var i, h, e;
if(!impl.events.hasOwnProperty(e_name)) {
return this;
}
e = impl.events[e_name];
// don't allow a handler to be attached more than once to the same event
for(i=0; i<e.length; i++) {
h = e[i];
if(h[0] === fn && h[1] === cb_data && h[2] === cb_scope) {
return this;
}
}
e.push([ fn, cb_data || {}, cb_scope || null ]);
// Attach unload handlers directly to the window.onunload and
// window.onbeforeunload events. The first of the two to fire will clear
// fn so that the second doesn't fire. We do this because technically
// onbeforeunload is the right event to fire, but all browsers don't
// support it. This allows us to fall back to onunload when onbeforeunload
// isn't implemented
if(e_name === 'page_unload') {
impl.addListener(w, "unload",
function() {
if(fn) {
fn.call(cb_scope, null, cb_data);
}
fn=cb_scope=cb_data=null;
}
);
impl.addListener(w, "beforeunload",
function() {
if(fn) {
fn.call(cb_scope, null, cb_data);
}
fn=cb_scope=cb_data=null;
}
);
}
return this;
},
addVar: function(name, value) {
if(typeof name === "string") {
impl.vars[name] = value;
}
else if(typeof name === "object") {
var o = name, k;
for(k in o) {
if(o.hasOwnProperty(k)) {
impl.vars[k] = o[k];
}
}
}
return this;
},
removeVar: function() {
var i, params;
if(!arguments.length) {
return this;
}
if(arguments.length === 1
&& Object.prototype.toString.apply(arguments[0]) === "[object Array]") {
params = arguments[0];
}
else {
params = arguments;
}
for(i=0; i<params.length; i++) {
if(impl.vars.hasOwnProperty(params[i])) {
delete impl.vars[params[i]];
}
}
return this;
},
sendBeacon: function() {
var k, url, img, nparams=0;
// At this point someone is ready to send the beacon. We send
// the beacon only if all plugins have finished doing what they
// wanted to do
for(k in this.plugins) {
if(this.plugins.hasOwnProperty(k)) {
if(impl.disabled_plugins[k]) {
continue;
}
if(!this.plugins[k].is_complete()) {
return this;
}
}
}
// If we reach here, all plugins have completed
impl.fireEvent("before_beacon", impl.vars);
// Don't send a beacon if no beacon_url has been set
if(!impl.beacon_url) {
return this;
}
url = impl.beacon_url + '?v=' + encodeURIComponent(BOOMR.version);
for(k in impl.vars) {
if(impl.vars.hasOwnProperty(k)) {
nparams++;
url += "&" + encodeURIComponent(k)
+ "=" + encodeURIComponent(impl.vars[k]);
}
}
// only send beacon if we actually have something to beacon back
if(nparams) {
img = new Image();
img.src=url;
}
return this;
},
randomNess: function() {
var randomnumber=Math.floor((Math.random()*100) + 1);
if (randomnumber <= impl.ratio) { return true;}
else { return false;}
}
};
var make_logger = function(l) {
return function(m, s) {
this.log(m, l, "boomerang" + (s?"."+s:"")); return this;
};
};
boomr.debug = make_logger("debug");
boomr.info = make_logger("info");
boomr.warn = make_logger("warn");
boomr.error = make_logger("error");
if(w.YAHOO && w.YAHOO.widget && w.YAHOO.widget.Logger) {
boomr.log = w.YAHOO.log;
}
else if(typeof w.Y !== "undefined" && typeof w.Y.log !== "undefined") {
boomr.log = w.Y.log;
}
else if(typeof console !== "undefined" && typeof console.log !== "undefined") {
boomr.log = function(m,l,s) { console.log(s + ": [" + l + "] ", m); };
}
for(k in boomr) {
if(boomr.hasOwnProperty(k)) {
BOOMR[k] = boomr[k];
}
}
BOOMR.plugins = BOOMR.plugins || {};
}(window));
// end of boomerang beaconing section
// Now we start built in plugins.
// This is the Round Trip Time plugin. Abbreviated to RT
// the parameter is the window
(function(w) {
var d=w.document;
BOOMR = BOOMR || {};
BOOMR.plugins = BOOMR.plugins || {};
// private object
var impl = {
complete: false, //! Set when this plugin has completed
timers: {}, //! Custom timers that the developer can use
// Format for each timer is { start: XXX, end: YYY, delta: YYY-XXX }
cookie: 'RT', //! Name of the cookie that stores the start time and referrer
cookie_exp:600, //! Cookie expiry in seconds
strict_referrer: true, //! By default, don't beacon if referrers don't match.
// If set to false, beacon both referrer values and let
// the back end decide
// The start method is fired on page unload. It is called with the scope
// of the BOOMR.plugins.RT object
start: function() {
var t_end, t_start = new Date().getTime();
// We use document.URL instead of location.href because of a bug in safari 4
// where location.href is URL decoded
if(!BOOMR.utils.setCookie(impl.cookie,
{ s: t_start, r: d.URL.replace(/#.*/, '') },
impl.cookie_exp,
"/", null)
) {
BOOMR.error("cannot set start cookie", "rt");
return this;
}
t_end = new Date().getTime();
if(t_end - t_start > 50) {
// It took > 50ms to set the cookie
// The user Most likely has cookie prompting turned on so
// t_start won't be the actual unload time
// We bail at this point since we can't reliably tell t_done
BOOMR.utils.removeCookie(impl.cookie);
// at some point we may want to log this info on the server side
BOOMR.error("took more than 50ms to set cookie... aborting: "
+ t_start + " -> " + t_end, "rt");
}
return this;
}
};
BOOMR.plugins.RT = {
// Methods
init: function(config) {
impl.complete = false;
impl.timers = {};
BOOMR.utils.pluginConfig(impl, config, "RT",
["cookie", "cookie_exp", "strict_referrer"]);
BOOMR.subscribe("page_ready", this.done, null, this);
BOOMR.subscribe("page_unload", impl.start, null, this);
return this;
},
startTimer: function(timer_name) {
if(timer_name) {
impl.timers[timer_name] = { start: new Date().getTime() };
impl.complete = false;
}
return this;
},
endTimer: function(timer_name, time_value) {
if(timer_name) {
impl.timers[timer_name] = impl.timers[timer_name] || {};
if(typeof impl.timers[timer_name].end === "undefined") {
impl.timers[timer_name].end =
(typeof time_value === "number" ? time_value : new Date().getTime());
}
}
return this;
},
setTimer: function(timer_name, time_delta) {
if(timer_name) {
impl.timers[timer_name] = { delta: time_delta };
}
return this;
},
// Called when the page has reached a "usable" state. This may be when the
// onload event fires, or it could be at some other moment during/after page
// load when the page is usable by the user
done: function() {
var t_start, u, r, r2,
subcookies, basic_timers = { t_done: 1, t_resp: 1, t_page: 1},
ntimers = 0, t_name, timer, t_other=[],
ti, p;
if(impl.complete) {
return this;
}
// If the dev has already called endTimer, then this call will do nothing
// else, it will stop the page load timer
this.endTimer("t_done");
// A beacon may be fired automatically on page load or if the page dev fires
// it manually with their own timers. It may not always contain a referrer
// (eg: XHR calls). We set default values for these cases
// use document.URL instead of location.href because of a safari bug
u = d.URL.replace(/#.*/, '');
r = r2 = d.referrer.replace(/#.*/, '');
subcookies = BOOMR.utils.getSubCookies(BOOMR.utils.getCookie(impl.cookie));
BOOMR.utils.removeCookie(impl.cookie);
if(subcookies !== null
&& typeof subcookies.s !== "undefined"
&& typeof subcookies.r !== "undefined"
) {
r = subcookies.r;
if(!impl.strict_referrer || r === r2) {
t_start = parseInt(subcookies.s, 10);
}
}
if(!t_start) {
// TODO: Change the "warn" to "info" (or drop it) once the WebTiming API
// becomes standard (2012? 2014?) Scream at me if you see this past 2012
BOOMR.warn("start cookie not set, trying WebTiming API", "rt");
// Get start time from WebTiming API see:
// http://dev.w3.org/2006/webapi/WebTiming/
// http://blogs.msdn.com/b/ie/archive/2010/06/28/measuring-web-page-performance.aspx
// http://blog.chromium.org/2010/07/do-you-know-how-slow-your-web-page-is.html
p = w.performance || w.msPerformance || w.webkitPerformance || w.mozPerformance;
if(p && p.timing) {
ti = p.timing;
}
else if(w.chrome && w.chrome.csi) {
// Older versions of chrome also have a timing API that's sort of documented here:
// http://ecmanaut.blogspot.com/2010/06/google-bom-feature-ms-since-pageload.html
// source here:
// http://src.chromium.org/viewvc/chrome/trunk/src/chrome/renderer/loadtimes_extension_bindings.cc?view=markup
ti = {
requestStart: w.chrome.csi().startE
};
}
if(ti) {
// First check if requestStart is set. It will be 0 if
// the page were fetched from cache. If so, check fetchStart
// which should always be there except if not implemented. If
// not, then look at navigationStart. If none are set, we
// leave t_start alone so that timers that depend on it don't
// get sent back.
t_start = ti.requestStart
|| ti.fetchStart
|| ti.navigationStart
|| undefined;
}
else {
BOOMR.warn("This browser doesn't support the WebTiming API", "rt");
}
}
// make sure old variables don't stick around
BOOMR.removeVar('t_done', 't_page', 't_resp', 'u', 'r', 'r2');
for(t_name in impl.timers) {
if(!impl.timers.hasOwnProperty(t_name)) {
continue;
}
timer = impl.timers[t_name];
// if delta is a number, then it was set using setTimer
// if not, then we have to calculate it using start & end
if(typeof timer.delta !== "number") {
if(typeof timer.start !== "number") {
timer.start = t_start;
}
timer.delta = timer.end - timer.start;
}
// If the caller did not set a start time, and if there was no start cookie
// then timer.delta will be NaN, in which case we discard it.
if(isNaN(timer.delta)) {
continue;
}
if(basic_timers.hasOwnProperty(t_name)) {
BOOMR.addVar(t_name, timer.delta);
}
else {
t_other.push(t_name + '|' + timer.delta);
}
ntimers++;
}
// At this point we decide whether the beacon should be sent or not
if(ntimers) {
BOOMR.addVar({ "u": u, "r": r });
if(r2 !== r) {
BOOMR.addVar("r2", r2);
}
if(t_other.length) {
BOOMR.addVar("t_other", t_other.join(','));
}
}
impl.timers = {};
impl.complete = true;
BOOMR.sendBeacon(); // we call sendBeacon() anyway because some other plugin
// may have blocked waiting for RT to complete
return this;
},
is_complete: function() { return impl.complete; }
};
}(window));
// End of RT plugin
// This is the Bandwidth & Latency plugin abbreviated to BW
// the parameter is the window
(function(w) {
var d=w.document;
BOOMR = BOOMR || {};
BOOMR.plugins = BOOMR.plugins || {};
// We choose image sizes so that we can narrow down on a bandwidth range as
// soon as possible the sizes chosen correspond to bandwidth values of
// 14-64kbps, 64-256kbps, 256-1024kbps, 1-2Mbps, 2-8Mbps, 8-30Mbps & 30Mbps+
// Anything below 14kbps will probably timeout before the test completes
// Anything over 60Mbps will probably be unreliable since latency will make up
// the largest part of download time. If you want to extend this further to
// cover 100Mbps & 1Gbps networks, use image sizes of 19,200,000 & 153,600,000
// bytes respectively
// See https://spreadsheets.google.com/ccc?key=0AplxPyCzmQi6dDRBN2JEd190N1hhV1N5cHQtUVdBMUE&hl=en_GB
// for a spreadsheet with the details
var images=[
{ name: "image-0.png", size: 11483, timeout: 1400 },
{ name: "image-1.png", size: 40658, timeout: 1200 },
{ name: "image-2.png", size: 164897, timeout: 1300 },
{ name: "image-3.png", size: 381756, timeout: 1500 },
{ name: "image-4.png", size: 1234664, timeout: 1200 },
{ name: "image-5.png", size: 4509613, timeout: 1200 },
{ name: "image-6.png", size: 9084559, timeout: 1200 }
];
images.end = images.length;
images.start = 0;
// abuse arrays to do the latency test simply because it avoids a bunch of
// branches in the rest of the code.
// I'm sorry Douglas
images.l = { name: "image-l.gif", size: 35, timeout: 1000 };
// private object
var impl = {
// properties
base_url: 'images/',
timeout: 15000,
nruns: 5,
latency_runs: 10,
user_ip: '',
cookie_exp: 7*86400,
cookie: 'BA',
// state
results: [],
latencies: [],
latency: null,
runs_left: 0,
aborted: false,
complete: false,
running: false,
// methods
ncmp: function(a, b) { return (a-b); },
iqr: function(a)
{
var l = a.length-1, q1, q3, fw, b = [], i;
q1 = (a[Math.floor(l*0.25)] + a[Math.ceil(l*0.25)])/2;
q3 = (a[Math.floor(l*0.75)] + a[Math.ceil(l*0.75)])/2;
fw = (q3-q1)*1.5;
l++;
for(i=0; i<l && a[i] < q3+fw; i++) {
if(a[i] > q1-fw) {
b.push(a[i]);
}
}
return b;
},
calc_latency: function()
{
var i, n,
sum=0, sumsq=0,
amean, median,
std_dev, std_err,
lat_filtered;
// We first do IQR filtering and use the resulting data set
// for all calculations
lat_filtered = this.iqr(this.latencies.sort(this.ncmp));
n = lat_filtered.length;
BOOMR.debug(lat_filtered, "bw");
// First we get the arithmetic mean, standard deviation and standard error
// We ignore the first since it paid the price of DNS lookup, TCP connect
// and slow start
for(i=1; i<n; i++) {
sum += lat_filtered[i];
sumsq += lat_filtered[i] * lat_filtered[i];
}
n--; // Since we started the loop with 1 and not 0
amean = Math.round(sum / n);
std_dev = Math.sqrt( sumsq/n - sum*sum/(n*n));
// See http://en.wikipedia.org/wiki/1.96 and http://en.wikipedia.org/wiki/Standard_error_%28statistics%29
std_err = (1.96 * std_dev/Math.sqrt(n)).toFixed(2);
std_dev = std_dev.toFixed(2);
n = lat_filtered.length-1;
median = Math.round(
(lat_filtered[Math.floor(n/2)] + lat_filtered[Math.ceil(n/2)]) / 2
);
return { mean: amean, median: median, stddev: std_dev, stderr: std_err };
},
calc_bw: function()
{
var i, j, n=0,
r, bandwidths=[], bandwidths_corrected=[],
sum=0, sumsq=0, sum_corrected=0, sumsq_corrected=0,
amean, std_dev, std_err, median,
amean_corrected, std_dev_corrected, std_err_corrected, median_corrected,
nimgs, bw, bw_c;
for(i=0; i<this.nruns; i++) {
if(!this.results[i] || !this.results[i].r) {
continue;
}
r=this.results[i].r;
// the next loop we iterate through backwards and only consider the largest
// 3 images that succeeded that way we don't consider small images that
// downloaded fast without really saturating the network
nimgs=0;
for(j=r.length-1; j>=0 && nimgs<3; j--) {
// if we hit an undefined image time, we skipped everything before this
if(typeof r[j] === 'undefined') {
break;
}
if(r[j].t === null) {
continue;
}
n++;
nimgs++;
// multiply by 1000 since t is in milliseconds and not seconds
bw = images[j].size*1000/r[j].t;
bandwidths.push(bw);
bw_c = images[j].size*1000/(r[j].t - this.latency.mean);
bandwidths_corrected.push(bw_c);
}
}
BOOMR.debug('got ' + n + ' readings', "bw");
BOOMR.debug('bandwidths: ' + bandwidths, "bw");
BOOMR.debug('corrected: ' + bandwidths_corrected, "bw");
// First do IQR filtering since we use the median here
// and should use the stddev after filtering.
if(bandwidths.length > 3) {
bandwidths = this.iqr(bandwidths.sort(this.ncmp));
bandwidths_corrected = this.iqr(bandwidths_corrected.sort(this.ncmp));
} else {
bandwidths = bandwidths.sort(this.ncmp);
bandwidths_corrected = bandwidths_corrected.sort(this.ncmp);
}
BOOMR.debug('after iqr: ' + bandwidths, "bw");
BOOMR.debug('corrected: ' + bandwidths_corrected, "bw");
// Now get the mean & median.
// Also get corrected values that eliminate latency
n = Math.max(bandwidths.length, bandwidths_corrected.length);
for(i=0; i<n; i++) {
if(i<bandwidths.length) {
sum += bandwidths[i];
sumsq += Math.pow(bandwidths[i], 2);
}
if(i<bandwidths_corrected.length) {
sum_corrected += bandwidths_corrected[i];
sumsq_corrected += Math.pow(bandwidths_corrected[i], 2);
}
}
n = bandwidths.length;
amean = Math.round(sum/n);
std_dev = Math.sqrt(sumsq/n - Math.pow(sum/n, 2));
std_err = Math.round(1.96 * std_dev/Math.sqrt(n));
std_dev = Math.round(std_dev);
n = bandwidths.length-1;
median = Math.round(
(bandwidths[Math.floor(n/2)] + bandwidths[Math.ceil(n/2)]) / 2
);
n = bandwidths_corrected.length;
amean_corrected = Math.round(sum_corrected/n);
std_dev_corrected = Math.sqrt(sumsq_corrected/n - Math.pow(sum_corrected/n, 2));
std_err_corrected = (1.96 * std_dev_corrected/Math.sqrt(n)).toFixed(2);
std_dev_corrected = std_dev_corrected.toFixed(2);
n = bandwidths_corrected.length-1;
median_corrected = Math.round(
(
bandwidths_corrected[Math.floor(n/2)]
+ bandwidths_corrected[Math.ceil(n/2)]
) / 2
);
BOOMR.debug('amean: ' + amean + ', median: ' + median, "bw");
BOOMR.debug('corrected amean: ' + amean_corrected + ', '
+ 'median: ' + median_corrected, "bw");
return {
mean: amean,
stddev: std_dev,
stderr: std_err,
median: median,
mean_corrected: amean_corrected,
stddev_corrected: std_dev_corrected,
stderr_corrected: std_err_corrected,
median_corrected: median_corrected
};
},
defer: function(method)
{
var that=this;
return setTimeout(function() { method.call(that); that=null;}, 10);
},
load_img: function(i, run, callback)
{
var url = this.base_url + images[i].name
+ '?t=' + (new Date().getTime()) + Math.random(),
timer=0, tstart=0,
img = new Image(),
that=this;
img.onload=function() {
img.onload=img.onerror=null;
img=null;
clearTimeout(timer);
if(callback) {
callback.call(that, i, tstart, run, true);
}
that=callback=null;
};
img.onerror=function() {
img.onload=img.onerror=null;
img=null;
clearTimeout(timer);
if(callback) {
callback.call(that, i, tstart, run, false);
}
that=callback=null;
};
// the timeout does not abort download of the current image, it just sets an
// end of loop flag so we don't attempt download of the next image we still
// need to wait until onload or onerror fire to be sure that the image
// download isn't using up bandwidth. This also saves us if the timeout
// happens on the first image. If it didn't, we'd have nothing to measure.
timer=setTimeout(function() {
if(callback) {
callback.call(that, i, tstart, run, null);
}
},
images[i].timeout
+ Math.min(400, this.latency ? this.latency.mean : 400)
);