Unhandled Exception in Windows Service

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G

Guest

Hello,

I need to know if the AppDomain.UnhandledException event can be handled
using a Windows Service. I've create a Windows Service that uses the
Exception Handling Applilcation Block and there are certain exceptoions that
I want bubbled up as unhandled exceptions so in the Main method I add a
method for handling Unhandled Exceptions.

The code never seems to get hit.

Doing some research, I remember that the UnhandledException event is
specific to one app domain. When the ServiceBase.Run(ServiceBase[]) method
is called, I am assuming each servicebase is created in its own app domain.
So for kicks I added the UnhandledException assignment to both the service
constructor and the OnStart method, neither of which seems to have worked
either.

Does this even work from a Windows Service?

Please advise.

Thanks,

The Man From SQL
 
Hi,

Thanks for your post!

Yes, based on my test, the AppDomain.UnhandledException event is not
called, if the exception is generated in Windows Service application. I
suspect this is caused by special feature of Windows Service, I will
perform some deeper research on it and try to find out the root cause. I
will update you ASAP. Thanks.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
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Jeffrey,

Thanks so much for your quick response. I look forward to any insights you
can offer.

TheManFromSQL
 
Hi,

I still did not get any insight regarding this issue yet, I will try to
give it a consulting with the CLR team. Thanks for your patient!

Best regards,
Jeffrey Tan
Microsoft Online Community Support
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Hi,

Sorry for letting you wait.

I finally found out the root cause. The OnStop method of ServiceBase is
triggerred by ServiceBase.DeferredStop method. Using Reflector, we can see
the source code like this:

private unsafe void DeferredStop()
{
fixed (NativeMethods.SERVICE_STATUS* service_statusRef1 =
&this.status)
{
int num1 = this.status.currentState;
this.status.checkPoint = 0;
this.status.waitHint = 0;
this.status.currentState = 3;
NativeMethods.SetServiceStatus(this.statusHandle,
service_statusRef1);
try
{
this.OnStop();
this.WriteEventLogEntry(Res.GetString("StopSuccessful"));
this.status.currentState = 1;
NativeMethods.SetServiceStatus(this.statusHandle,
service_statusRef1);
}
catch (StackOverflowException)
{
throw;
}
catch (OutOfMemoryException)
{
throw;
}
catch (ThreadAbortException)
{
throw;
}
catch (Exception exception1)
{
this.WriteEventLogEntry(Res.GetString("StopFailed", new
object[] { exception1.ToString() }), EventLogEntryType.Error);
this.status.currentState = num1;
}
}
}
As you can see, the DeferredStop method catched all the exceptions, so the
exception in the OnStop method will not trigger our
AppDomain.UnhandledException event. So was DeferredPause for OnPause
method.

Hope this helps.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
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most efficient resolution. The offering is not appropriate for situations
that require urgent, real-time or phone-based interactions or complex
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Hi Jeffrey,

Thanks so much for your diligence. This might answer my question after all.

One more question: the exception I am encountering actually doesn't occur
in the OnStop method or the OnShutDown method. It occurs in a thread pool
thread spawned when my timer.elapsed event is called.

Would the thread exception cause DeferredStop to be called?

Thanks again for your help,

TheManFromSql



"Jeffrey Tan[MSFT]" said:
Hi,

Sorry for letting you wait.

I finally found out the root cause. The OnStop method of ServiceBase is
triggerred by ServiceBase.DeferredStop method. Using Reflector, we can see
the source code like this:

private unsafe void DeferredStop()
{
fixed (NativeMethods.SERVICE_STATUS* service_statusRef1 =
&this.status)
{
int num1 = this.status.currentState;
this.status.checkPoint = 0;
this.status.waitHint = 0;
this.status.currentState = 3;
NativeMethods.SetServiceStatus(this.statusHandle,
service_statusRef1);
try
{
this.OnStop();
this.WriteEventLogEntry(Res.GetString("StopSuccessful"));
this.status.currentState = 1;
NativeMethods.SetServiceStatus(this.statusHandle,
service_statusRef1);
}
catch (StackOverflowException)
{
throw;
}
catch (OutOfMemoryException)
{
throw;
}
catch (ThreadAbortException)
{
throw;
}
catch (Exception exception1)
{
this.WriteEventLogEntry(Res.GetString("StopFailed", new
object[] { exception1.ToString() }), EventLogEntryType.Error);
this.status.currentState = num1;
}
}
}
As you can see, the DeferredStop method catched all the exceptions, so the
exception in the OnStop method will not trigger our
AppDomain.UnhandledException event. So was DeferredPause for OnPause
method.

Hope this helps.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
==================================================
Get notification to my posts through email? Please refer to
http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif
ications.

Note: The MSDN Managed Newsgroup support offering is for non-urgent issues
where an initial response from the community or a Microsoft Support
Engineer within 1 business day is acceptable. Please note that each follow
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professional working with you may need further investigation to reach the
most efficient resolution. The offering is not appropriate for situations
that require urgent, real-time or phone-based interactions or complex
project analysis and dump analysis issues. Issues of this nature are best
handled working with a dedicated Microsoft Support Engineer by contacting
Microsoft Customer Support Services (CSS) at
http://msdn.microsoft.com/subscriptions/support/default.aspx.
==================================================
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Click to expand...
 
Hi,

I assume you are using System.Timers.Timer component. In this component,
Timer.Elapsed event is triggered by System.Timers.Timer.MyTimerCallback
method. It is this method that catches all the exceptions, below is the
source code comes from Reflector:

private void MyTimerCallback(object state)
{
if (state == this.cookie)
{
if (!this.autoReset)
{
this.enabled = false;
}
Timer.FILE_TIME file_time1 = new Timer.FILE_TIME();
Timer.GetSystemTimeAsFileTime(ref file_time1);
ElapsedEventArgs args1 = new
ElapsedEventArgs(file_time1.ftTimeLow, file_time1.ftTimeHigh);
try
{
if (this.onIntervalElapsed != null)
{
if ((this.SynchronizingObject != null) &&
this.SynchronizingObject.InvokeRequired)
{

this.SynchronizingObject.BeginInvoke(this.onIntervalElapsed, new object[] {
this, args1 });
}
else
{
this.onIntervalElapsed(this, args1);
}
}
}
catch (Exception)
{
}
}
}
So AppDomain.UnhandledException is not fired at all.

Hope this helps.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
==================================================
Get notification to my posts through email? Please refer to
http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif
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most efficient resolution. The offering is not appropriate for situations
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http://msdn.microsoft.com/subscriptions/support/default.aspx.
==================================================
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