Python script running as Windows service: Clean shutdown

[Stefan Krah]

Hello,

I'm trying to run a Python script as a Windows service with a defined
shutdown. The script (enigma-client.py) handles the communications with
the server in a distributed computing effort and calls a C program
(enigma.exe) to do the computations.

enigma.exe should save its current state when receiving SIGINT or SIGTERM.
This (obviously) works under Unix and also when running the script from the
Windows command line and terminating it with Ctrl-C.

I understand that for a clean shutdown of a Windows service one would
have to use the win32 extensions and have the working thread check
for the shutdown event in short intervals (<ddtp0q$jga$1 at online.de>).


This would leave me with these options:

 a) Write enigma-client.py as a service. Write enigma.exe as a
    service and have it poll regularly for shutdown events.

 b) Have enigma.exe save its state regularly, use srvany.exe
    and forget about a graceful shutdown.


I'm new to Windows services, so I'd be grateful for corrections or
better solutions. Here is relevant part of the code (The whole thing
is at http://www.bytereef.org/enigma-client.txt ):



""" main """
cmdline = 'enigma.exe -R 00trigr.naval 00bigr.naval 00ciphertext > NUL'
eclient = Eclient()

if len(sys.argv) != 3:
    eclient.usage()

if os.path.isfile(LOCKFILE):
    print "enigma-client: error: found lockfile %s. \n" \
          "Check that no other enigma-client process is using this directory." \
          % LOCKFILE
    sys.exit(1)

atexit.register(eclient.rm_lockfile)
eclient.touch_lockfile()

win32process.SetPriorityClass(
   win32process.GetCurrentProcess(),
   win32process.IDLE_PRIORITY_CLASS
)

while 1:
    retval =  os.system(cmdline) >> 8
    if retval == 0:
        eclient.submit_chunk(sys.argv[1], int(sys.argv[2]))
        eclient.get_chunk(sys.argv[1], int(sys.argv[2]))
    elif retval == 1:
        eclient.get_chunk(sys.argv[1], int(sys.argv[2]))
        time.sleep(10)
    else:
        """./enigma has caught a signal"""
        sys.exit(retval)



Stefan Krah

-- 
Break original Enigma messages:  http://www.bytereef.org/m4_project.html