IE double postback hangs IIS 7 in Integrated Managed pipeline mode when session is accessed

Question

Here\'s my environment: IIS7.5 on Win 7, .NET 4, App Pool Integrated

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Answer 1

I had a similar issue on my site. In my case I had a page that contained a number of grids that each called a asmx webservice to retrieve their data. If the user navigated away from the page before all of the web requests had completed, then that user's session could become very slow (at least a couple of minutes to load a page), but other users' sessions would be unaffected by the slowness. For me, the issue began when I installed .NET 4.5 on the server.

I found a page here: http://forums.asp.net/t/1888889.aspx/1?Question+regarding+a+possible+bug+within+NET+4+5 that talks about this being a known issue with .NET 4.5. The bug can be triggered if site is using integrated mode and the browser disconnects while waiting for a page that's using the ASP.NET session. (See post for more details).

I believe that your double-postback case might cause the browser to abandon one of the requests, so it seems like this would apply. In addition, I and others have noticed that the bug seems to be more commonly seen when using IE (although this is just a coincidence - it's not an IE bug)

The post also describes a workaround (adjusting the uploadReadAheadSize setting in the web.config), and that workaround solved the problem for me.

Answer 2

From your description it looks like IIS deadlocks when it tries to acquire the session object for your request. I wouldn't be looking for a reason in the browsers because this can only be a server side issue. And probably one you can't do much about. If it is a deadlock, than it's a multi-threaded, timing dependent problem. So if different browsers send requests with slightly different timing, you get different results. Also if you run the browsers locally or remotely, you get slightly different timings. Emptying the session doesn't help because the problem is on session acquisition. Disabling the session completely does help, because the session isn't acquired at all. Changing the AppPool to Classic helps because it has a different implementation of Session management which doesn't have the deadlock. To test the hypothesis, you can try inserting an artificial delay between the postbacks on the client side. This will create different timing conditions and should affect the problem.

I have to say that these are just speculations based on your description and my experience with IIS. I would suggest that you change the AppPool to Classic because the performance downside aren't that huge.

Answer 3

Good news! It appears that the session blocking issue has been resolved after installing .Net 4.5.1

I've upgraded my testing machine 7.5.7600.16385 on Windows Server 2008 R2 with .Net 4.5 installed to 4.5.1 and the issue went away!

Answer 4

Please note that this is same as Stackoverflow post --> ManagedPipelineHandler for an AJAX POST crashes if an IE9 user navigates away from a page while that call was in progress.

This appears to be a regression in ASP.NET 4.5. ASP.NET team is working on a patch, but there is a temporary workaround (see the post referred above).

If you cannot wait for public broad update, you can contact Microsoft customer support for hotfix requests. Just follow the regular process of opening a support case. For example, file online https://support.microsoft.com/oas/default.aspx?&gprid=548&&st=1&wfxredirect=1&sd=gn or call support http://support.microsoft.com/default.aspx?id=fh;en-us;offerprophone. You may need to pay minimal amount upfront but you may get refund based on customer support policies. Just ask customer support professional to contact netfx45compat at Microsoft dot com to get quick context on this issue.

Thanks Varun Gupta (.NET Framework Compatibility)