ThreadAbortException and Unmanaged Code

pedramr — Tue, 02 Oct 2007 15:04:00 GMT

As you are probably aware Thread.Abort() raises a ThreadAbortException in the thread on which it is invoked, to begin the process of terminating the thread.

Please note that if Abort is called on a managed thread while it is executing unmanaged code, a ThreadAbortException is not thrown until the thread returns to managed code. That is also true when performing a COM Interop or P-Invoke. However if you have a ServicedComponent, the exception is received by the thread inside the component as expected. For instance if you are in an ASP.NET application and a timeout is occurred (timeout is communicated in terms of a ThreadAbortException) the exception is raised inside the component.

How the Execution Timeout is managed in ASP.NET

pedramr — Tue, 02 Oct 2007 12:13:00 GMT

As you are probably aware, it is possible to specify the execution timeout of an ASP.NET request through the config file. All you need to do is to set the executionTimeout attribute on the httpRuntime element in either the web.config (for one ASP.NET application) or even the machine.config (to affect all ASP.NET applications):

According to the online documentation the executionTimeout is a TimeSpan attribute that “specifies the maximum number of seconds that a request is allowed to execute before being automatically shut down by ASP.NET”. (BTW, it doesn’t work in debug mode)

The default value for this attribute has been set to 90 seconds in ASP.NET 1.x and was increased to 110 seconds in ASP.NET 2.0.

Internally the timeout is managed by a timer (an instance of a System.Threading.Timer class) which is fired every 15 seconds.

Internally ASP.NET uses a Timer (an instance of System.Threading.Timer) to invoke the request cancelation process. This timer is fired once every 15 seconds, so if the executionTimeout is set to 3 seconds, in reality the request can timeout at any time between 3 seconds and 18 seconds.

When the timer is fired, a thread from the ThreadPool is used to check all the requests. The ones that have timed out are sent a ThreadAbortException by calling Abort on the thread executing the request.

So as per above, the executionTimeout only specifies the minimum duration that the request is guaranteed to be executed. The actual timeout can happen between executionTimeout and executionTimeout + 15 seconds.

Pedram Rezaei's Ramblings : ASP.NET

ThreadAbortException and Unmanaged Code

How the Execution Timeout is managed in ASP.NET