Re: A Very Troubled Application...

Yes, I'd be curious as well as to how the system cleans up after a fault.  I
know yesterday when I intentionally caused the app to crash numerous times
my system (Windows XP Pro) became unstable in that Explorer would just
randomly "hang" and not let you utilize the task bar; it was ridiculous.

I have a similar situation that I'm working on where instead of using Word
I'm using some other 3rd party app that behaves very poorly but the issue is
moot since I must use it and must adapt it to be a "server"
non-user-monitored application.  I'm well on my way to it and I've done a
majority of the work but solving cases where the application just fails is a
very difficult endeavor.

On Wed, Jun 10, 2009 at 11:22 AM, Adam Tuliper <[email protected]>wrote:

> we had to do the same hacks for word.. using it as server side doc
> generation before good pdf components were available to us and I recall
> word
> would fail after a while. that goodness we've come a long way  : )
>
> For dlls being cleaned at termination time.. library code segments are
> shared between processes (that reference the same lib). So there is only
> one
> code section in memory (unless specifically designated otherwise I
> believe).
> When LoadLibrary is called, ref count is incremented. So when a process
> crashes.. how does the system know what to decrement counts for? I don't
> believe it does.. and hence a potential memory issue with crashed
> appliations leaving resources around.  If I'm not 100% correct on this.. I
> would like to know a reference to how the system cleans up.. Id be curious
> of the inner workings, this is all from rusty memory.
>
>
>
>
>
> On Wed, Jun 10, 2009 at 2:01 AM, Peter vd Weerd <[email protected]> wrote:
>
> > When windows terminates a process, all system-resources are cleaned up.
> > Dll's too. They are loaded in the virtual address space, and the address
> > space is removed at termination.
> > Reference counting on dll's is only within a process. AFAIK there is no
> > system-wide refcnt.
> >
> > Dll's are loaded by creating a named filemapping to this dll. This
> mapping
> > is a normal system resource and will be freed at termination time.
> >
> > Out of process COM objects are a different story. The process where this
> > COM-object lives has nothing to do with the hosting process (as far as
> the
> > system knowns). And it is refcnted.
> >
> > So if the host process is getting terminated, the only way for the COM
> > process to get auto terminated is to do a watchdog check on its host if
> its
> > still alive. There are some watchdog checks in the standard marshalling
> code
> > (hartbeats), but I'm not sure if they are used for terminating the
> process
> > with the COM object. Another question is how big the timeout for this
> > watchdog is. So may be you want to restart the COM object before the
> > watchdog timed out.
> >
> > I used my proposed solution (restarting the process after failure) a few
> > times in case of untrusted applications, and it worked fine. I can
> remember
> > problems with MSWord (out of process COM) years ago. After failure (the
> > process using MSWord died) I killed the MSWord instance too and than
> > restarted my application. Ugly, but it worked.
> > I had more problems there, because word was not designed as a service.
> Its
> > a UI, so it will popup a dialog every now and than. I had to 'answer'
> those
> > dialogs too :-)
> >
> > /Peter
> > ----- Original Message ----- From: "Adam Tuliper" <
> [email protected]>
> > To: <[email protected]>
> > Sent: Tuesday, June 09, 2009 10:30 PM
> > Subject: Re: [ADVANCED-DOTNET] A Very Troubled Application...
> >
> >
> >
> >  I seem to recall the opposite was true.. Windows isn't very good about
> >> cleaning up resources (at least in the past) because of the way
> libraries
> >> dont get freed because the reference count handling is never executed..
> >> something along those lines. Although if someone can provide some more
> >> technical reference on if this is true or not.. Id love to read it.
> >>
> >>
> >>
> >> On Tue, Jun 9, 2009 at 1:00 PM, Peter vd Weerd <[email protected]>
> wrote:
> >>
> >>  Mike,
> >>>
> >>> In general: if you have access violations caused by COM-components, its
> >>> not
> >>> a good idea to recover from that.
> >>> If you can isolate the complete application to a kind of a
> >>> worker-process,
> >>> you write a controller-program that starts this worker-process, and if
> it
> >>> fails, just start a new one.
> >>>
> >>> Windows is very good in recovering from crashed processes: all
> resources
> >>> are freed. So, when the controller process fires up a new
> worker-process
> >>> its
> >>> a brand new one with clean memory, a clean .NET virtual machine, etc.
> >>>
> >>> /Peter
> >>>
> >>>
> >>> ----- Original Message ----- From: "Mike Andrews" <
> >>> [email protected]>
> >>> To: <[email protected]>
> >>> Sent: Tuesday, June 09, 2009 6:06 PM
> >>> Subject: [ADVANCED-DOTNET] A Very Troubled Application...
> >>>
> >>>
> >>>
> >>> I have a very troubled application (not mine but a 3rd party) that
> likes
> >>> to
> >>>
> >>>> fail with various Unhandled exceptions (memory access and others) when
> >>>> certain files are loaded (I have no idea of the reason).  Sometimes
> >>>> loading
> >>>> a file causes a COM exception to occur (no one knows why and it's very
> >>>> unlikely that the manufacturer will ever fix it).  This causes the
> >>>> entire
> >>>> application to crash (and/or provide some other unpredictable
> behavior).
> >>>> This does not occur most of the time but only occasionally.  However I
> >>>> must
> >>>> account for these eventualities as this process will be running on
> >>>> multiple
> >>>> servers and I need it the most stable I can get it.
> >>>>
> >>>> What I have been doing is looking for the process in the process list
> >>>> and
> >>>> then killing it.  That works most of the time but when one of those
> >>>> dialogs
> >>>> is thrown up asking you to click OK it really messes things up.  I've
> >>>> started looking for the dialog, but the time when the dialog appears
> >>>> varies
> >>>> so any predictability is out.
> >>>>
> >>>> What I need to know is if it's possible to attach a hook (or some
> other
> >>>> such
> >>>> mechanism) to the window to intercept any unhandled win32 exceptions
> >>>> similar
> >>>> to the capability available in the .NET framework.  I'm at my wit's
> end
> >>>> here
> >>>> on this one.  I need to create something stable enough so I can
> recover
> >>>> on
> >>>> the server and continue.
> >>>>
> >>>> Any help or information would be most appreciated.
> >>>>
> >>>> Thanks,
> >>>> Mike
> >>>>
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