hello world singleton daemon

openaps-dbus

#!/usr/bin/python

#!/usr/bin/python
import gobject
import dbus.service
import time
import sys

# http://cyberelk.net/tim/2011/08/16/d-bus-and-python-asynchronous-method-implementation/
# https://coelhorjc.wordpress.com/2014/12/09/howto-write-dbus-service-for-linux-in-python/
# http://stackoverflow.com/questions/34851085/how-to-stop-a-dbus-gobject-loop/34860020#34860020

BUS='com.example.Timer'
IFACE='com.example.Timer'
PATH='/com/example/Timer'
START_TIME=time.time ()

class Timer(dbus.service.Object):
    def __init__ (self, loop):
        self.loop = loop
        self.bus = dbus.SessionBus ()
        request = self.bus.request_name(BUS, dbus.bus.NAME_FLAG_DO_NOT_QUEUE)
        if request != dbus.bus.REQUEST_NAME_REPLY_EXISTS:
          bus_name = dbus.service.BusName (BUS, bus=self.bus)
          dbus.service.Object.__init__ (self, bus_name, PATH)
        else:
          print "running already"
          # raise Exception("Already exists")

    @dbus.service.method(dbus_interface=IFACE,
                         in_signature='i',
                         out_signature='i',
                         async_callbacks=('reply_handler',
                                          'error_handler'))
    def Delay (self, seconds, reply_handler, error_handler):
        print "Sleeping for %ds" % seconds
        gobject.timeout_add_seconds (seconds,
                                     lambda: reply_handler (seconds))

    @dbus.service.method(dbus_interface=IFACE,
                         in_signature='', out_signature='')
    def Howdy(self):
      print "Howdy!"

    @dbus.service.method(dbus_interface=IFACE,
                         in_signature='', out_signature='s')
    def Start (self):
      print "Howdy!"
      return "OK"

    @dbus.service.method(dbus_interface=IFACE,
                         in_signature='', out_signature='')
    def Exit(self):
      print "Exiting!"
      self.loop.quit()

def heartbeat():
    print "Still alive at", time.time () - START_TIME
    return True

if __name__ == '__main__':
  from dbus.mainloop.glib import DBusGMainLoop
  DBusGMainLoop (set_as_default=True)
  loop = gobject.MainLoop ()
  dbus.mainloop.glib.threads_init( )
  # Start the heartbeat
  handle = gobject.timeout_add_seconds (1, heartbeat)
  print "STarting", sys.argv
  timer = Timer (loop)
  request = timer.bus.request_name(BUS, dbus.bus.NAME_FLAG_DO_NOT_QUEUE)
  if request != dbus.bus.REQUEST_NAME_REPLY_EXISTS:
    # Start the D-Bus service
    app = timer
    loop.run ()
    print loop
  else:
    print "Already running", 'running howdy'
    proxy = timer.bus.get_object(BUS, PATH)
    app = dbus.Interface (proxy, IFACE)
    print app
    app.Howdy( )