Gape between http requests in the browser - loading media resources - performance

I get this delay (first image below) of almost 4s before the media resources start downloading, for the scond request the gap is negligible.
Even when I allow the browser to use the cache, the same behavior occurs.
I tried to load the media resources after DOMContentLoaded event but I got the same behavior.
First Request URL : http://subdomain_1.domain.com (HTML content loaded in ~3s )
Second Request URL : http://subdomain_2.domain.com (HTML content loaded in ~1s )
Can someone please help me with this?
Thanks!!

I Added a 1s timeout to avoid the gape i.e. to load media ressources after DOMContentLoaded event.

Related

IIIF implementation (Loris + Mirador)

I am trying to implement the IIIF standard in order to show some papyri. I have configured Loris as an image server (here there is an info.json example: https://philhist-papyri-01.philhist.unibas.ch/loris/1/images/1.RectoIliad19th(T)book-IR-enh.jpg/info.json) and also I have configured Mirador. I am also serving manifests via an API (example: https://philhist-papyri-01.philhist.unibas.ch/api/iiif/11b4ca60-6bac-11eb-a1e6-005056b34690/manifest).
When I try to load the images in Mirador, I am getting an error:
Tile push../node_modules/openseadragon/build/openseadragon/openseadragon.js.$.Tile failed to load: https, https://philhist-papyri-01.philhist.unibas.ch, philhist-papyri-01.philhist.unibas.ch/6%2Fimages%2F6.VersoUnidentifiedLiteraryText-IR.jpg/full/4,/0/default.jpg - error: Image load aborted
Does anybody have any idea why this is coming from? The image actually can be retrieved from the URI in the manifest (https://philhist-papyri-01.philhist.unibas.ch/loris/1/images/1.RectoIliad19th(T)book-IR-enh.jpg/full/full/0/default.jpg), but it is not being shown in the mirador window.
There might be an issue with the resolver of Loris which is causing the #id of the image not to be canonical, but I am not quite sure.
I'm seeing an issue that perhaps CORS is not enabled for your info.json responses.
See: https://projectmirador.org/embed/?iiif-content=https://philhist-papyri-01.philhist.unibas.ch/api/iiif/11b4ca60-6bac-11eb-a1e6-005056b34690/manifest
Depending on how you use Loris to serve content, you will need to enable CORS for the IIIF requests.

What is "initiator other" in network in chrome console?

I fire an image tag when someone converts on our website for reporting and analytics:
<img src="https://example.evyy.net/conv/?somechannel=cats&cid=3790&oid=123&cat1=premium&sku1=123&qty1=1&amt1=456&custid=qbc" />
We noticed traffic decline yesterday. To debug I visited the site and signed up, with the console open network tab.
I typed "evyy" into the filter box and I see 3 line items for my tag.
What does this mean? Should there not be just 1 line item? One item has a 302 status and the other two a status of 200. That's good right?
Screen attached. Does this look "right"? Is there any drill down in the network tab I can look at to see if there is a problem on our end with tracking?
"Initiator Other" usually means the network request was made from a user, not from Chrome, a redirect or a script.
The request was fired when someone clicked a button (this is what your analytics is probably tracking). You can read more about this in the Chrome DevTools docs.
Initiator: The object or process that initiated the request. It can have one of the following values:
Parser - Chrome's HTML parser initiated the request.
Redirect - A HTTP redirect initiated the request.
Script - A script initiated the request.
Other - Some other process or action initiated the request, such as the user navigating to a page via a link, or by entering a URL in the address bar.
The requests are made in the order you see, the first received the 302 response which said, "hey, go to this new url". That's (probably) why the second request was made, which got the 200. The third was probably from clicking on the button too. Looks fine to me.
I noticed another case not related with a user action:
<link rel="icon" type="image/jpeg" href="image.jpg" />
... causes the image.jpg to get loaded with "Initiator Other" (also true with images of another format).
(wanted to add this as a comment under the previous answer, but I am not allowed to)
One case where initiator type is 'other' is when a request gets redirected, in this scenario the redirected request will have initiator as other.
For Example: request was made for url1 which got redirected to url2, now in case of url2 we get initiator type as 'other'

Symfony2, jQuery Ajax request, web debug toolbar, 500 Internal Server Error

I am developing an application with Symfony2 platform that, at one moment, makes a simple AJAX request on document ready.
jQuery.ajax({
url: 'test.php',
type: 'POST',
data: {
'test': 'test'
},
success: function( response ){
jQuery( 'div#container' ).html( response );
}
});
The problem is that on app_dev.php, where the debug toolbar is loaded, an 500 error is throwed.
More precisely, the AJAX response from the 'test.php' file is received and loaded in the div container, but then, when it tries to load the toolbar, I receive an alert message:
"An error occured while loading the web debug toolbar (500: Internal
Server Error). Do you want to open the profiler?"
If I open profiler, I don't see anything wrong.
If I open the xhr request for the toolbar, a FastCGI 500 error is displayed:
Module FastCgiModule
Notification ExecuteRequestHandler
Handler PHP54_via_FastCGI
Error Code 0x000000ff
If I don't try to make the AJAX request, the toolbar is loaded with no problem.
If I make the request by hand (event on a button) after the toolbar is loaded, again, no problem. If I make the request by hand (event on a button) before the toolbar is loaded the error is throwed.
Notes:
This error occur only on the local machine (with ISS 7.5, PHP 5.4.14). On the production server (IIS server 8.0, same and PHP) the AJAX request is made, and the toolbar is loaded with no problems. I have replaced the php.ini on the local machine with the php.ini from the production server - same problem.
Initialy AJAX request was loading the result of a simple bundle controller method, but then I have tried with a simple PHP file 'test.php', same problem.
I have tried with post and get methods to make the request.
Does anyone have any ideea what goes wrong?
This is not a serious problem since I have multiple options the develop this app, but is bugging me, and I already lost a enough time with this.
PS: if it make any difference, on same machine I have developed an application - no framework - that makes, multiple simultaneos ajax requests.
The following will not fix your error, but provides an alternative way to possibly achieve your need. It seems you want to load asynchronously a part of your website, Symfony2 provides a solution for that: ESI render.
The doc is here: http://symfony.com/doc/current/book/templating.html#asynchronous-content-with-hinclude-js
This method will create an ajax call only then your page will be rendered.

Serving content depending on http accept header - caching problems?

I'm developing an application which is supposed to serve different content for "normal" browser requests and AJAX requests for the same URL requested.
(in fact, encapsulate the response HTML in JSON object if the request is AJAX).
For this purpose, I'm detecting an AJAX request on the server side, and processing the response appropriately, see the pseudocode below:
function process_response(request, response)
{
if request.is_ajax
{
response.headers['Content-Type'] = 'application/json';
response.headers['Cache-Control'] = 'no-cache';
response.content = JSON( some_data... )
}
}
The problem is that when the first AJAX request to the currently viewed URL is made strange things happens on Google Chrome - if, right after the response comes and is processed via JavaScript, user clicks some link (static, which redirects to other page) and then clicks back button in the browser, he sees the returned JSON code instead of the rendered website (logging the server I can say that no request is made). It seems for me that Chrome stores the latest request response for the specific URL, and doesn't take into account that it has different content-type etc.
Is that a bug in the Chrome or am I misusing HTTP protocol ?
--- update 12 11 2012, 12:38 UTC
following PatrikAkerstrand answer, I've found following Chrome bug: http://code.google.com/p/chromium/issues/detail?id=94369
any ideas how to avoid this behaviour?
You should also include a Vary-header:
response.headers['Vary'] = 'Content-Type'
Vary is a standard way to control caching context in content negotiation. Unfortunately it has also buggy implementations in some browsers, see Browser cache vary broken.
I would suggest using unique URLs.
Depending of you framework capabilities you can redirect (302) the browser to URL + .html to force response format and make cache key unique within browser session. Then for AJAX requests you can still keep suffix-less URL. Alternatively you may suffix AJAX URL with .json instead .
Another options are: prefixing AJAX requests with /api or adding some cache boosting query params ?rand=1234.
Setting cache-control to no-store made it in my case, while no-cache didn't. This may have unwanted side effects though.
no-store: The response may not be stored in any cache. Although other directives may be set, this alone is the only directive you need in preventing cached responses on modern browsers.
Source: Mozilla Developer Network - HTTP Cache-Control

What does status=canceled for a resource mean in Chrome Developer Tools?

What would cause a page to be canceled? I have a screenshot of the Chrome Developer Tools.
This happens often but not every time. It seems like once some other resources are cached, a page refresh will load the LeftPane.aspx. And what's really odd is this only happens in Google Chrome, not Internet Explorer 8. Any ideas why Chrome would cancel a request?
We fought a similar problem where Chrome was canceling requests to load things within frames or iframes, but only intermittently and it seemed dependent on the computer and/or the speed of the internet connection.
This information is a few months out of date, but I built Chromium from scratch, dug through the source to find all the places where requests could get cancelled, and slapped breakpoints on all of them to debug. From memory, the only places where Chrome will cancel a request:
The DOM element that caused the request to be made got deleted (i.e. an IMG is being loaded, but before the load happened, you deleted the IMG node)
You did something that made loading the data unnecessary. (i.e. you started loading a iframe, then changed the src or overwrite the contents)
There are lots of requests going to the same server, and a network problem on earlier requests showed that subsequent requests weren't going to work (DNS lookup error, earlier (same) request resulted e.g. HTTP 400 error code, etc)
In our case we finally traced it down to one frame trying to append HTML to another frame, that sometimes happened before the destination frame even loaded. Once you touch the contents of an iframe, it can no longer load the resource into it (how would it know where to put it?) so it cancels the request.
status=canceled may happen also on ajax requests on JavaScript events:
<script>
$("#call_ajax").on("click", function(event){
$.ajax({
...
});
});
</script>
<button id="call_ajax">call</button>
The event successfully sends the request, but is is canceled then (but processed by the server). The reason is, the elements submit forms on click events, no matter if you make any ajax requests on the same click event.
To prevent request from being cancelled, JavaScript event.preventDefault(); have to be called:
<script>
$("#call_ajax").on("click", function(event){
event.preventDefault();
$.ajax({
...
});
});
</script>
NB: Make sure you don't have any wrapping form elements.
I had a similar issue where my button with onclick={} was wrapped in a form element. When clicking the button the form is also submitted, and that messed it all up...
Another thing to look out for could be the AdBlock extension, or extensions in general.
But "a lot" of people have AdBlock....
To rule out extension(s) open a new tab in incognito making sure that "allow in incognito is off" for the extention(s) you want to test.
In my case, I found that it is jquery global timeout settings, a jquery plugin setup global timeout to 500ms, so that when the request exceed 500ms, chrome will cancel the request.
You might want to check the "X-Frame-Options" header tag. If its set to SAMEORIGIN or DENY then the iFrame insertion will be canceled by Chrome (and other browsers) per the spec.
Also, note that some browsers support the ALLOW-FROM setting but Chrome does not.
To resolve this, you will need to remove the "X-Frame-Options" header tag. This could leave you open to clickjacking attacks so you will need to decide what the risks are and how to mitigate them.
Here's what happened to me: the server was returning a malformed "Location" header for a 302 redirect.
Chrome failed to tell me this, of course. I opened the page in firefox, and immediately discovered the problem.
Nice to have multiple tools :)
Another place we've encountered the (canceled) status is in a particular TLS certificate misconfiguration. If a site such as https://www.example.com is misconfigured such that the certificate does not include the www. but is valid for https://example.com, chrome will cancel this request and automatically redirect to the latter site. This is not the case for Firefox.
Currently valid example: https://www.pthree.org/
A cancelled request happened to me when redirecting between secure and non-secure pages on separate domains within an iframe. The redirected request showed in dev tools as a "cancelled" request.
I have a page with an iframe containing a form hosted by my payment gateway. When the form in the iframe was submitted, the payment gateway would redirect back to a URL on my server. The redirect recently stopped working and ended up as a "cancelled" request instead.
It seems that Chrome (I was using Windows 7 Chrome 30.0.1599.101) no longer allowed a redirect within the iframe to go to a non-secure page on a separate domain. To fix it, I just made sure any redirected requests in the iframe were always sent to secure URLs.
When I created a simpler test page with only an iframe, there was a warning in the console (which I had previous missed or maybe didn't show up):
[Blocked] The page at https://mydomain.com/Payment/EnterDetails ran insecure content from http://mydomain.com/Payment/Success
The redirect turned into a cancelled request in Chrome on PC, Mac and Android. I don't know if it is specific to my website setup (SagePay Low Profile) or if something has changed in Chrome.
Chrome Version 33.0.1750.154 m consistently cancels image loads if I am using the Mobile Emulation pointed at my localhost; specifically with User Agent spoofing on (vs. just Screen settings).
When I turn User Agent spoofing off; image requests aren't canceled, I see the images.
I still don't understand why; in the former case, where the request is cancelled the Request Headers (CAUTION: Provisional headers are shown) have only
Accept
Cache-Control
Pragma
Referer
User-Agent
In the latter case, all of those plus others like:
Cookie
Connection
Host
Accept-Encoding
Accept-Language
Shrug
I got this error in Chrome when I redirected via JavaScript:
<script>
window.location.href = "devhost:88/somepage";
</script>
As you see I forgot the 'http://'. After I added it, it worked.
Here is another case of request being canceled by chrome, which I just encountered, which is not covered by any of answers up there.
In a nutshell
Self-signed certificate not being trusted on my android phone.
Details
We are in development/debug phase. The url is pointing to a self-signed host. The code is like:
location.href = 'https://some.host.com/some/path'
Chrome just canceled the request silently, leaving no clue for newbie to web development like myself to fix the issue. Once I downloaded and installed the certificate using the android phone the issue is gone.
If you use axios it can help you
// change timeout delay:
instance.defaults.timeout = 2500;
https://github.com/axios/axios#config-order-of-precedence
For my case, I had an anchor with click event like
<a href="" onclick="somemethod($index, hour, $event)">
Inside click event I had some network call, Chrome cancelling the request. The anchor has href with "" means, it reloads the page and the same time it has click event with network call that gets cancelled. Whenever i replace the href with void like
<a href="javascript:void(0)" onclick="somemethod($index, hour, $event)">
The problem went away!
If you make use of some Observable-based HTTP requests like those built-in in Angular (2+), then the HTTP request can be canceled when observable gets canceled (common thing when you're using RxJS 6 switchMap operator to combine the streams). In most cases it's enough to use mergeMap operator instead, if you want the request to complete.
I had faced the same issue, somewhere deep in our code we had this pseudocode:
create an iframe
onload of iframe submit a form
After 2 seconds, remove the iframe
thus, when the server takes more than 2 seconds to respond the iframe to which the server was writing the response to, was removed, but the response was still to be written , but there was no iframe to write , thus chrome cancelled the request, thus to avoid this I made sure that the iframe is removed only after the response is over, or you can change the target to "_blank".
Thus one of the reason is:
when the resource(iframe in my case) that you are writing something in, is removed or deleted before you stop writing to it, the request will be cancelled
I have embedded all types of font as well as woff, woff2, ttf when I embed a web font in style sheet. Recently I noticed that Chrome cancels request to ttf and woff when woff2 is present. I use Chrome version 66.0.3359.181 right now but I am not sure when Chrome started canceling of extra font types.
We had this problem having tag <button> in the form, that was supposed to send ajax request from js. But this request was canceled, due to browser, that sends form automatically on any click on button inside the form.
So if you realy want to use button instead of regular div or span on the page, and you want to send form throw js - you should setup a listener with preventDefault function.
e.g.
$('button').on('click', function(e){
e.preventDefault();
//do ajax
$.ajax({
...
});
})
I had the exact same thing with two CSS files that were stored in another folder outside my main css folder. I'm using Expression Engine and found that the issue was in the rules in my htaccess file. I just added the folder to one of my conditions and it fixed it. Here's an example:
RewriteCond %{REQUEST_URI} !(images|css|js|new_folder|favicon.ico)
So it might be worth you checking your htaccess file for any potential conflicts
happened to me the same when calling a. js file with $. ajax, and make an ajax request, what I did was call normally.
In my case the code to show e-mail client window caused Chrome to stop loading images:
document.location.href = mailToLink;
moving it to $(window).load(function () {...}) instead of $(function () {...}) helped.
In can this helps anybody I came across the cancelled status when I left out the return false; in the form submit. This caused the ajax send to be immediately followed by the submit action, which overwrote the current page. The code is shown below, with the important return false at the end.
$('form').submit(function() {
$.validator.unobtrusive.parse($('form'));
var data = $('form').serialize();
data.__RequestVerificationToken = $('input[name=__RequestVerificationToken]').val();
if ($('form').valid()) {
$.ajax({
url: this.action,
type: 'POST',
data: data,
success: submitSuccess,
fail: submitFailed
});
}
return false; //needed to stop default form submit action
});
Hope that helps someone.
For anyone coming from LoopbackJS and attempting to use the custom stream method like provided in their chart example. I was getting this error using a PersistedModel, switching to a basic Model fixed my issue of the eventsource status cancelling out.
Again, this is specifically for the loopback api. And since this is a top answer and top on google i figured i'de throw this in the mix of answers.
For me 'canceled' status was because the file did not exist. Strange why chrome does not show 404.
It was as simple as an incorrect path for me. I would suggest the first step in debugging would be to see if you can load the file independently of ajax etc.
The requests might have been blocked by a tracking protection plugin.
It happened to me when loading 300 images as background images. I'm guessing once first one timed out, it cancelled all the rest, or reached max concurrent request. need to implement a 5-at-a-time
One the reasons could be that the XMLHttpRequest.abort() was called somewhere in the code, in this case, the request will have the cancelled status in the Chrome Developer tools Network tab.
In my case, it started coming after chrome 76 update.
Due to some issue in my JS code, window.location was getting updated multiple times which resulted in canceling previous request.
Although the issue was present from before, chrome started cancelling request after update to version 76.
I had the same issue when updating a record. Inside the save() i was prepping the rawdata taken from the form to match the database format (doing a lot of mapping of enums values, etc), and this intermittently cancels the put request. i resolved it by taking out the data prepping from the save() and creating a dedicated dataPrep() method out of it. I turned this dataPrep into async and await all the memory intensive data conversion. I then return the prepped data to the save() method that i could use in the http put client. I made sure i await on dataPrep() before calling the put method:
await dataToUpdate = await dataPrep();
http.put(apiUrl, dataToUpdate);
This solved the intermittent cancelling of request.

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