[python-win32] Re: wmi + pythonservice : multithreading issue s

[Aloys Baillet]

Thank you very much for your explainations!
I was'n aware of this pythoncom.CoInitialize function.
For the threading thing, you are absolutely right, and I don't usually
do things like that, it was just a quick and dirty test script to show
you my problem...
And finally, for the service, I didn't try with the pywin32 service, and
I totally believe you if you say it works. I just forgot to say that I
use the py2exe module to generate my service, and I did get the same
error with it... I will try with the CoInitialize to see if it works!
Again, thank you for the time you spent on my problem, and for your
kindness in showing me my errors!

--
Aloys Baillet - R&D @ La Maison

Tim Golden wrote:
> [Aloys Baillet]
> | <code>
> | import wmi
> | import threading
> | 
> | class lmPerformancesInfos(threading.Thread):
> |      def __init__(self):
> |          threading.Thread.__init__(self)
> |          print 'In Main Thread'
> |          c = wmi.WMI ()
> |          for process in c.Win32_Process ():
> |            print process.ProcessId, process.Name
> | 
> |      def run(self):
> |          print 'In Another Thread...'
> |          c = wmi.WMI ()
> |          while 1:
> |              for process in c.Win32_Process ():
> |                print process.ProcessId, process.Name
> | 
> | if __name__ == '__main__':
> |      perfs = lmPerformancesInfos()
> |      perfs.start()
> | 
> | </code>
> 
> [... snip resulting error ...]
> 
> Well, a couple of things occur to me here, one
> definitely pertinent, the other less so. 
> 
> First, whenever you're using COM/DCOM in anything other
> than the main thread of a program, you need to call 
> pythoncom.CoInitialize () first. Just one of those things.
> 
> Secondly, I'm not sure that you entirely understand the
> way the threading.Thread class is supposed to work. There
> are, of course, several ways to do things, but the usual
> approach is to create one or more subthreads from the main
> program thread (ie from what you usually think of as the
> program) and then to start those threads. By virtue of the
> way Python works, anything in the Thread __init__ will in
> effect be called in the main thread, before the subthread
> has started, but it's not the most logical place.
> 
> The code below does, I believe, what your code sample
> did, and doesn't give any errors. 
> 
> <code>
> import pythoncom
> import wmi
> import threading
> 
> class lmPerformancesInfos(threading.Thread):
>    def __init__(self):
>      threading.Thread.__init__(self)
> 
>    def run(self):
>      print 'In Another Thread...'
>      pythoncom.CoInitialize ()
>      c = wmi.WMI ()
>      while 1:
>        for process in c.Win32_Process ():
>          print process.ProcessId, process.Name
> 
> if __name__ == '__main__':
>    print 'In Main Thread'
>    c = wmi.WMI ()
>    for process in c.Win32_Process ():
>      print process.ProcessId, process.Name
> 
>    perfs = lmPerformancesInfos()
>    perfs.start()
> </code>
> 
> Having said all that, I've not encountered this particular 
> problem in a service, with or without a CoInitialize. For
> example, the following code works:
> 
> <code>
> import os, sys
> import threading
> import time
> 
> import win32serviceutil
> import win32service
> import win32event
> 
> import wmi
> 
> class Service (win32serviceutil.ServiceFramework):
>   _svc_name_ = "WMIService"
>   _svc_display_name_ = "WMI Service"
> 
>   def __init__ (self, args):
>     win32serviceutil.ServiceFramework.__init__ (self, args)
>     self.hWaitStop = win32event.CreateEvent (None, 0, 0, None)
>     self.computer = wmi.WMI ()
>     open ("c:/temp/wmi-service.log", "w").write ("Started at %s\n" %
> time.asctime ())
> 
>   def SvcStop (self):
>     self.ReportServiceStatus (win32service.SERVICE_STOP_PENDING)
>     win32event.SetEvent (self.hWaitStop)
> 
>   def SvcDoRun (self):
>     while 1:
>       result = win32event.WaitForSingleObject (self.hWaitStop, 5000)
>       if result == win32event.WAIT_TIMEOUT:
>         f = open ("c:/temp/wmi-service.log", "a")
>         f.write ("%s\n" % time.asctime ())
>         for i in self.computer.Win32_Process ():
>           f.write ("%s\n" % i.Caption)
>         f.close ()
>       else:
>         open ("c:/temp/wmi-service.log", "a").write ("Finished at %s\n" %
> time.asctime ())
>         break
> 
> if __name__ == '__main__':
>   win32serviceutil.HandleCommandLine (Service)
> </code>
> 
> I realise that by now you'll have implemented your performance
> code some other way, but I did want to take the opportunity to
> track down problems with WMI if there were any.
> 
> TJG
> 
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