Handling OOMs in new AppDomain

25 Nov 2007 8:32 PM

ttrudeau

Currently, I'm playing with some ideas on recycling application components
for a service application when the individual parts die, because of an OOM.
As a start to this I created a secondary AppDomain and created an instance of
a class in that application domain that throws an OutOfMemoryException on an
interval.

I hooked up the AppDomain.UnhandledException event, but it isn't getting
called. I can watch the output that says, "A first chance exception of type
'System.OutOfMemoryException' occurred in ..." But, nothing happens and the
class seems to continue on its merry way. The error is thrown by an event
handler (handling the Timer.Elapsed event).

What is the proper way to handle exceptions in this context?

26 Nov 2007 4:29 PM

Brian Gideon

On Nov 25, 2:32 pm, ttrudeau <ttrud***@discussions.microsoft.com>
wrote:

> Currently, I'm playing with some ideas on recycling application components
> for a service application when the individual parts die, because of an OOM.
> As a start to this I created a secondary AppDomain and created an instance of
> a class in that application domain that throws an OutOfMemoryException on an
> interval.
>
> I hooked up the AppDomain.UnhandledException event, but it isn't getting
> called. I can watch the output that says, "A first chance exception of type
> 'System.OutOfMemoryException' occurred in ..." But, nothing happens and the
> class seems to continue on its merry way. The error is thrown by an event
> handler (handling the Timer.Elapsed event).
>
> What is the proper way to handle exceptions in this context?

Are you trying to isolate memory leaks? Recycling application domains
may not fix the problem especially if the leak is occurring in
unmanaged code.

26 Nov 2007 5:35 PM

ttrudeau

Initially I'm focusing on OOM issues, but really any unhandled exception.
After that I'll move into some health monitoring to ensure there are no
endless loops, etc. The different objects will be running user developed
code and workflows, so I cannot guarantee the reliability of those parts, but
I do want to be able to guarantee the reliability of the service as a whole.

Do you have any other suggestions if loading and unloading an application
domain will not provide that reliability?

--
Tony Trudeau
Senior Software Developer
Die-Tech Industries, Inc.

Show quote

"Brian Gideon" wrote:
> Are you trying to isolate memory leaks? Recycling application domains
> may not fix the problem especially if the leak is occurring in
> unmanaged code.

27 Nov 2007 2:11 AM

Brian Gideon

On Nov 26, 11:35 am, ttrudeau <ttrud***@discussions.microsoft.com>
wrote:
Show quote

> Initially I'm focusing on OOM issues, but really any unhandled exception.
> After that I'll move into some health monitoring to ensure there are no
> endless loops, etc. The different objects will be running user developed
> code and workflows, so I cannot guarantee the reliability of those parts, but
> I do want to be able to guarantee the reliability of the service as a whole.
>
> Do you have any other suggestions if loading and unloading an application
> domain will not provide that reliability?
>
> --
> Tony Trudeau
> Senior Software Developer
> Die-Tech Industries, Inc.
>
>
>
> "Brian Gideon" wrote:
> > Are you trying to isolate memory leaks? Recycling application domains
> > may not fix the problem especially if the leak is occurring in
> > unmanaged code.

Well, recycling application domains is definitely a good start at
increasing the reliability of the service especially since it sounds
like you'll have some sort of plugin architecture where you don't have
a lot of control over the plugin code. It should solve some OOM
exceptions.

As for the exception handling...I don't have lot of experience using
AppDomain.UnhandledException, but it sounds like the debugger may be
intercepting the exception before it is propagated to that event
handler. Have you tried testing the code outside of the debugger?

27 Nov 2007 5:05 AM

ttrudeau

That's an interesting idea. I just tried running it without the /DEBUG
switch to see what happens and the exceptions are still swallowed.

--
Tony Trudeau
Senior Software Developer
Die-Tech Industries, Inc.

Show quote

"Brian Gideon" wrote:

> > "Brian Gideon" wrote:
> Well, recycling application domains is definitely a good start at
> increasing the reliability of the service especially since it sounds
> like you'll have some sort of plugin architecture where you don't have
> a lot of control over the plugin code. It should solve some OOM
> exceptions.
>
> As for the exception handling...I don't have lot of experience using
> AppDomain.UnhandledException, but it sounds like the debugger may be
> intercepting the exception before it is propagated to that event
> handler. Have you tried testing the code outside of the debugger?
>