Debugging SignalR hang

Question

Windows 7, SignalR2.

I have some HelloWorld SignalR code that works in one VS2013 project (Ie, my SignalR hello world playground).

When I add the same code

Answer 1

We traced this problem back to Glimpse.ASPNet. It attaches itself to PreSendRequestHeaders. Therefore, if you use Glimpse.ASPNet with SignalR, you might find you get threads locking up "forever".

Removing Glimpse.AspNet fixes the problem

Answer 2

Do you happen to have an Application_PreSendRequestHeaders method defined or are you in some other way attached to the HttpApplication.PreSendRequestHeaders event?

I ask, because this seems to be the same issue reported here. For at least some people on that thread, removing the PreSendRequestHeaders event handler resolved the issue.

While we recommend you never use the PreSendRequestHeaders event, we are actively working on this issue so we can get a fix out for 2.1.1.

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If you are not attaching to the PreSendRequestHeaders event, we (the SignalR team) could use your help. So far, we have not been able to reproduce this issue without attaching to the PreSendRequestHeaders event. If you could provide us with an application that doesn't attach to this event, yet still hangs in this manner, we would greatly appreciate it.

The previous version of SignalR (2.0.3), did not make requests to /signalr/start and does not experience this hang. So you can temporarily work around this issue by downgrading from SignalR 2.1.0 to 2.0.3 until 2.1.1 is released.