503 error with radasyncupload URGENT!!

[Kiran]

We are just now starting to transition to the RadAsyncUpload using a custom HTTP Handler.  The reason for this is that we want to directly pass the files to a WCF service that will scan the file for viruses, encrypt, and store the files as they come in. 

The problem is that when a few people are uploading files at the same time, everybody seems to get hosed and we start getting a 503 error returned to us (can't even go back to the page because we'll get that 503 error).  Is there some configuration change I need to make at the WCF, IIS, or web.config level to accommodate many users uploading large files (anywhere from 1k to 200mb)? 

The applications that are using the RadAsyncUpload are SharePoint 2010 webparts and application pages.  Everythign seems to work fine if a user only uploads 1 file or if there is only one user of the system at any particular time.

UPDATE: Using Firebug, I was able to see that the calls to the custom handler are being aborted.  I use the same 6 test files every time I test this issue.  The first and second time I upload all 6 files, everything works fine.  At some point though, any file I upload just stops uploading (or at least that's how it seems). 

[Hristo Valyavicharski]

Hi Kiran,

There are a few things that may cause this error. Please read Mike's blog article, where he explains in details what cause this error and how to resolve it.

Regards,
Hristo Valyavicharski
Telerik

[BRiddle]

I am also having an HTTP 503 problem out of RadAsyncUpload but with different circumstances than on this thread. 

I have a largely ASP.Net MVC5 web application which is all MVC with Telerik UI for ASP.Net MVC 2016.1.226.0 except one ASP.Net Webform page for large file uploads via chunked uploads via RadAsyncUpload from Telerik UI for ASP.Net Ajax  16.1.113.0.  The files being uploaded are Windows memory dumps typically ranging in size from about 250KB up to around 8GB.  (The app is a UI in front of an automated memory dump analysis service).

The file upload has worked well so far except for one file being uploaded from one Support employee in a remote location about 1,500 miles away.  He tried to use the UI to upload a 2GB dump file from within IE11 on Win7x64.  The upload will run up until around 1.2GB and then would simply stop upload progress with no errors showing on the client-side and no errors logged on the server side.

I've searched the Telerik support forms and read entries like the " 503 error with radasyncupload URGENT!! - AsyncUpload - UI ..." thread and the links from that write-up in the "Where did my IIS7 server go? Troubleshooting 503 "service unavailable" errors" link.   My problem seems different in that it seems to be an IE-specific problem.   There are no matching errors in the server's Application Event Log.  The IIS log shows HTTP 200 responses to each chunk at the time the upload stops.   There are no errors in the server-side ELMAH logs.  The service's UI remains responsive throughout to other users.  There are no issues even with IE for this user until after a full GB of file has already successfully been uploaded.

My question to our Telerik community here is what types of things can cause the following symptoms and is there anything you can recommend to help identify the problem?  This app is in Beta before being released for use throughout the company and I'm being asked to explain this upload failure before the app goes fully live.

1.)  The error is repeatable when he's using IE11 against the app and always seems to happen within a few percentage complete points of the same place in the file (percent complete as displayed by RadAsyncUpload's UI).

2.)  The error does not happen if he runs the same UI and steps through FireFox.   The whole file uploads without incident. There is also no error if he uploads the file to the same server via FTP.  We can sucessfully upload the same file via IE from a different machine; though that second machine is here on the same campus LAN as the server rather than being on the remote campus LAN.

3.)   I had him capture two memory dumps of IE; one when he noticed the upload complete percentage had stopped progressing and another 5 minutes later.    IE does not appear to be generally hung and is not showing errors that are obvious to me (though I rarely look at IE dumps and may just be missing finding such an error).  Only one thread accumulated any CPU time at all during the interim and that thread is making a network call via WinInet and doing a WaitForMultipleObjects on two (undefined in a single application process dump) event handles.

4.)  Originally the upload page's "OnClientFileUploadFailed" event did not fire at all.   After noticing the function wininet!InternetConfirmZoneCrossingA() in one of the involved threads' callstacks in the IE dumps, I had him add the UI's URL to IE's "Trusted Sites" list.  After that change to IE's security zones, the UploadFailed event does fire when the upload stops progressing and displays the resulting eventArgs.get_message() as an HTTP 503 error.

5.) The user's IE is using the IE defaults of 8 max connections to a server and the default timeout settings.

I'm out of ideas and know of no other error monitoring or logging techniques for either the Telerik control or for the other involved software to help either make this user's error go away or at least explain what's happening and why it only seems to happen with IE.   Is there a way to enable more error logging in RadAsyncUpload on either client side or server side?

Thanks!
-Bob

[Hristo Valyavicharski]

Hi Bob,

Try to disable Custom Error Pages and look in the returned response. There should be an error message:

After we see the error message we can tell you what cause this error.

Regards,
Hristo Valyavicharski
Telerik