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      1 # Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
      2 # Use of this source code is governed by a BSD-style license that can be
      3 # found in the LICENSE file.
      4 
      5 """
      6 Provides utility class for stopping and restarting services
      7 
      8 When using this class, one likely wishes to do the following:
      9 
     10     def initialize(self):
     11         self._services = service_stopper.ServiceStopper(['service'])
     12         self._services.stop_services()
     13 
     14 
     15     def cleanup(self):
     16         self._services.start_services()
     17 
     18 As this ensures that the services will be off before the test code runs, and
     19 the test framework will ensure that the services are restarted through any
     20 code path out of the test.
     21 """
     22 
     23 import logging
     24 
     25 from autotest_lib.client.bin import utils
     26 from autotest_lib.client.common_lib import error
     27 
     28 
     29 class ServiceStopper(object):
     30     """Class to manage CrOS services.
     31     Public attributes:
     32       services_to_stop: list of services that should be stopped
     33 
     34    Public constants:
     35       POWER_DRAW_SERVICES: list of services that influence power test in
     36     unpredictable/undesirable manners.
     37 
     38     Public methods:
     39       stop_sevices: stop running system services.
     40       restore_services: restore services that were previously stopped.
     41 
     42     Private attributes:
     43       _services_stopped: list of services that were successfully stopped
     44     """
     45 
     46     POWER_DRAW_SERVICES = ['powerd', 'update-engine', 'bluetoothd', 'vnc']
     47 
     48     def __init__(self, services_to_stop=[]):
     49         """Initialize instance of class.
     50 
     51         By Default sets an empty list of services.
     52         """
     53         self.services_to_stop = services_to_stop
     54         self._services_stopped = []
     55 
     56 
     57     def stop_services(self):
     58         """Turn off managed services."""
     59 
     60         for service in self.services_to_stop:
     61             cmd = 'status %s' % service
     62             out = utils.system_output(cmd, ignore_status=True)
     63             is_stopped = 'start/running' not in out
     64             if is_stopped:
     65                 continue
     66             try:
     67                 utils.system('stop %s' % service)
     68                 self._services_stopped.append(service)
     69             except error.CmdError as e:
     70                 logging.warning('Error stopping service %s. %s',
     71                                 service, str(e))
     72 
     73 
     74     def restore_services(self):
     75         """Restore services that were stopped."""
     76         for service in reversed(self._services_stopped):
     77             utils.system('start %s' % service, ignore_status=True)
     78         self._services_stopped = []
     79 
     80 
     81     def __enter__(self):
     82         self.stop_services()
     83         return self
     84 
     85 
     86     def __exit__(self, exnval, exntype, exnstack):
     87         self.restore_services()
     88 
     89 
     90     def close(self):
     91         """Equivalent to restore_services."""
     92         self.restore_services()
     93