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We are hosting a web application on a series of Windows 7 machines (accessed via localhost), which has IIS 7.5, and some users are sporadically getting stuck in the middle of a request. After examining the IIS request logs, it is taking over 230,000 milliseconds on a specific Javascript file, roughly four minutes. It seems our server-side processing works fine and quickly, but the browser hangs as soon as it tries to bring in the Javascript file. It doesn't hang every time this file is requested, only occasionally. These problematic requests still yield an HTTP status code of 200 in the log, but a Win32 error code of 1236 (network connection aborted by the local system).

After the four minutes are up, it seems the browser no longer tries to make any more requests for the external resources (CSS files, images, etc), and just renders what it has thus far. So the user gets a plain white page with all the data in Times New Roman, no formatting, and no Javascript to dictate the behavior. They are stuck.

This problem only seems to happen to requests for this specific Javascript file, which is roughly 280KB. Another interesting thing to note is that when I make a manual GET request for this file from the browser address bar, it prompts me to download it, but its appending six random numbers/letters to the file name when I go to save it, which I found to be completely strange. So I disabled static compression and the classic ASP buffering nonsense but we are still experiencing the issue. I did not find any ISAPI filters or any other option that could be doing this filename mangling.

Any ideas on how to resolve this annoying issue? The same application works fine on the majority of our other machines, there must something unique about this particular IIS configuration that is causing these woes.

Josh Stodola
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    There's a few things missing from your question: 1) The application pool config for the site - is this Classic or Integrated pipeline mode 2) Is this a Classic ASP, ASP.NET, PHP? 3) Is it just a single user accessing the app? – Kev Feb 16 '12 at 14:57
  • @Kev Sorry for not providing enough details. It is a classic app pool. It is neither of the mentioned technologies, it an Xcentrisity BIS application, which I am not sure is relevant here because it is an ISAPI filter for .srf files only. Thanks for the help!!! – Josh Stodola Feb 16 '12 at 19:46
  • What about the third item I asked about? – Kev Feb 17 '12 at 11:46
  • @Kev Yes, single user – Josh Stodola Feb 17 '12 at 17:22
  • I believe this could be due to a commented out line in the HOSTS file for `localhost` to map to 127.0.0.1 this doesn't really explain why it works most of the time though. We did uncomment that and seem to no longer have the issue, but it will take a solid day or two of testing to confirm that. – Josh Stodola Feb 17 '12 at 17:23

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When I had seemingly random/periodic 1236 errors in IIS logs and request hangs the fix was to disable Windows Defender real-time scan.

Ryan
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