Python 3 Windows Service starts only in debug mode

Question

I first posted an answer in this post, but it didn't conform to the forum standards. I hope this time te answer fits the forum standards. This code should be more clear and easy to read.

In Python 3+ I have the following class that I use to build a Windows Service (it does nothing, just writes a log file):

#MyWindowsService.py
import win32serviceutil
import servicemanager
import win32service
import win32event
import sys
import logging
import win32api


class MyWindowsService(win32serviceutil.ServiceFramework):
    _svc_name_          = 'ServiceName'
    _svc_display_name_  = 'Service Display Name'
    _svc_description_   = 'Service Full Description'
    logging.basicConfig(
        filename    = 'c:\\Temp\\{}.log'.format(_svc_name_),
        level       = logging.DEBUG,
        format      = '%(levelname)-7.7s @ %(asctime)s: %(message)s'
    )

    def __init__(self, *args):
        self.log('Initializing service {}'.format(self._svc_name_))
        win32serviceutil.ServiceFramework.__init__(self, *args)
        self.stop_event = win32event.CreateEvent(None, 0, 0, None)

    def SvcDoRun(self):
        self.ReportServiceStatus(win32service.SERVICE_START_PENDING)
        try:
            self.log('START: Service start')
            self.ReportServiceStatus(win32service.SERVICE_RUNNING)
            self.start()
            win32event.WaitForSingleObject(self.stop_event, win32event.INFINITE)
        except Exception as e:
            self.log('Exception: {}'.format(e))
            self.SvcStop()

    def SvcStop(self):
        self.log('STOP: Service stopping...')
        self.ReportServiceStatus(win32service.SERVICE_STOP_PENDING)
        self.stop()
        win32event.SetEvent(self.stop_event)
        self.ReportServiceStatus(win32service.SERVICE_STOPPED)

    def log(self, msg):
        servicemanager.LogInfoMsg(str(msg))  #system log
        logging.info(str(msg))               #text log

    def start(self):
        self.runflag = True
        while self.runflag:
            win32api.Sleep((2*1000), True)
            self.log('Service alive')
    def stop(self): 
        self.runflag = False
        self.log('Stop received')




if __name__ == '__main__':
    win32serviceutil.HandleCommandLine(MyWindowsService)

In the script I use a log file to check if it's working properly. I'm running python3.6 (also tried with python3.4) on Windows 7 and I'm experiencing the following problem. When I run python MyWindowsService.py install the prompt says that the service has been installed (but nothing is written in the log file). If I try to start the service, I get Service Error: 1 - More info NET HELPMSG 3547 which doesn't say much about the error. If I run python MyWindowsService.py debug, the program runs just fine (the log file is written), but still I don't have any control over the service: if I open another prompt and try to stop/start the service I still got the same results as stated above.

I also tryed to insert some debug code inside the init function, and when I run python MyWindowsService.py install it seems it doesn't get called. Is it possible?

I've checked for multiple solution and workarounds around the net, but I didn't find anything suitable. What am I missing?

Answer 1

As pointed out by eriksun in the comment to the first post, the problem came from the location of the python script, that was in a drive mapped with an UNC path - I'm working with a virtual machine. Moving the python script in the same drive as the python installation did the job. To sum it up for future uses, if the service fails to start and you're pretty sure about your code, these are helpful actions to try and solve your issues:

• use sc start ServiceName, sc query ServiceName and sc stop ServiceName to get info about the service.
• check if your file is in a physical drive or in a UNC-mapped drive. If the latter try to run the script using the UNC path (for example python \\Server\share\python\your-folder\script.py) or move your script in the same drive as the python installation
• make sure that "python36.dll", "vcruntime140.dll", and "pywintypes36.dll" are either symlink'd to the directory that has PythonService.exe; or symlink'd to the System32 directory; or that the directories with these DLLs are in the system (not user) Path
• Check the system register with command reg query HKLM\System\CurrentControlSet\Services\your_service_name /s to get more information about the script

PLease, feel free to complete, change, modify the last so that it can be usefull for anyone that like me encounder this issue.

EDIT: One more thing... My project was thought to work actually with network folders (and UNC-mapped drive) and it failed when I tried to make it run as service. One very useful (day-saving) resource that I used to make it work is the SysinternalsSuite by Mark Russinovich that I found in this post. Hope this helps.