ASP.net: Concurrent file upload Fails after N number of large uploads

Question

I am working on an asp.net (Webforms, asp.net 2.0, Framework 3.5) application. It is 32 bit application running on IIS 7.0, with OS Windows 2008 R2 SP1

I am facing an issue with large file uploads. The files which are more than 20 MB or so. The application is able to upload large files however, it is noticed that after N number of uploads, the next set of uploads keep on failing until IIS is restarted.

The application supports concurrent file uploads. It is noticed that, single large file upload always works. Only when we start upload for more than 1 file, one of the uploads get stuck.

I tried looking at the temp folders in which posted file data gets uploaded and noticed that when the issue happens, the upload for the failing file never starts from server's view point as it never generates any temp file and after few sec, the request fails.

When the things fail, CPU is all OK W3wp stands at 2 GB memory usage (against total 4 GB RAM) W3wp does not show an crash as the other pages of the application still works fine

I tried using wireshark to see network traffic, but it also say ERR_connection_RESET. Apart from that, I am not getting any clue.

I am suspecting below things but not sure how to conclude or fix. 1) To start concurrent uploads, server needs to cop up with data pumping rate from client side and when it is unable to match that, it must be failing internally. This could be due to server's inability to server concurrent requests. 2) Frequent large uploads increases the memory footprint of the application to an extent where it cannot work with concurrent uploads, because to dump the files at temporary location in chunked manner, RAM is still required

Here is my web config setting

<httpRuntime maxRequestLength="2097151" executionTimeout="10800" enableVersionHeader="false"/>

From the implementation perspective, 1) We have client side implementation written in Java script, which creates FormData and sends the XHR to server 2) Server has a method which gets called when complete file is copied to server's temp directory, and we extract the file data using Request.Files collection and then processes further

When issue happens, the server method gets called, but the Request.Files comes empty.

Please let me know if anyone have very good insight on this which can guide me to the root cause and fix.

UPDATE: Client side code representation:

 //Set HTTP headers
_http.setRequestHeader("x-uploadmethod", "formdata");
_http.setRequestHeader("x-filename", "Name of file");

// Prepare form data
var data = new FormData();
data.append("Name of file", File contents);

//Sends XHR request
_http.send(data);

Server side code representation:

HttpFileCollection files = Request.Files;
int Id = objUpload.UploadMyAssets(files[0]);

The logic in UploadMyAssets is taking files[0] as HttpPostedFile and then move ahead with application specific logic.

Thanks

can you show your code thats completing and handling the uploads — Simon Price, Mar 28 '17 at 12:52
what are the flie types that these code blocks are in so that I can try and reproduce the issue — Simon Price, Mar 28 '17 at 13:18
Also, am I right in assuming that this is a WebForms project too? — Simon Price, Mar 28 '17 at 13:29
Yes, it is webforms project. All type of files are allowed. There is no restriction by type. In my use case, I typically take one PPT and one JPG — Nilesh Shah, Mar 28 '17 at 15:34
my apologies, i completely forgot about this, is it still an issue? — Simon Price, Apr 03 '17 at 10:32
Yes, there seems still an issue and unable to find an accurate root cause here. For now, the workaround is IIS restart every 2 days. — Nilesh Shah, Apr 03 '17 at 13:01
Ok, leave it with me and ill get my code all up for you and full explained — Simon Price, Apr 04 '17 at 07:38
Ive just looked across all my systems and cant find the code that I had, which is a shame as it was some of the most elegant code I had done for a client. — Simon Price, Apr 06 '17 at 18:48

score 0 · Answer 1 · answered Feb 13 '19 at 13:59

I had the same issue. Turns out ASP.NET Default Session Manager is blocking with async streams over https (HTTP/2). Didn't happen over http (non-ssl). Resolved this by using SessionStateBehavior.Readonly for the Controller Class. Related to this post: ASP.Net Asynchronous HTTP File Upload Handler

ASP.net: Concurrent file upload Fails after N number of large uploads

1 Answers1