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#!/usr/bin/python
# Copyright 2013 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Tool for running account manager as a daemon."""
import fcntl
import logging
import os
import signal
PIDFILE = '/var/run/manage_accounts.pid'
class AccountsManagerDaemon(object):
"""Creates a daemon process to run the accounts manager in."""
def __init__(self, pidfile, accounts_manager, fcntl_module=fcntl):
logging.debug('Initializing Daemon Module')
if not pidfile:
pidfile = PIDFILE
self.pidfile = pidfile
self.accounts_manager = accounts_manager
self.fcntl_module = fcntl_module
def StartDaemon(self):
"""Spins off a process that runs as a daemon."""
# To spin off the process, use what seems to be the "standard" way to spin
# off daemons: fork a child process, make it the session and process group
# leader, then fork it again so that the actual daemon process is no longer
# a session leader.
#
# This is a very simplified (with significantly reduced features) version of
# the python-daemon library at https://pypi.python.org/pypi/python-daemon/.
pid = os.fork()
logging.debug('Forked new process, pid= {0}'.format(pid))
if pid == 0:
os.setsid()
pid = os.fork()
if pid == 0:
os.chdir('/')
os.umask(0)
else:
# The use of os._exit here is recommended for parents of a daemon
# process to avoid issues with running the cleanup tasks that
# sys.exit() runs by preventing issues from the cleanup being run
# more than once when the two parents exit and later when the daemon
# exits.
os._exit(0)
else:
os._exit(0)
# Set up pidfile and signal handlers.
pidf = open(self.pidfile, 'w')
pidf.write(str(os.getpid()))
pidf.close()
logging.debug('Sending signal SIGTERM to shutdown daemon')
signal.signal(signal.SIGTERM, self.ShutdownDaemon)
self.accounts_manager.Main()
def ShutdownDaemon(self, signal_number, unused_stack_frame):
# Grab the lock on the lock file, ensuring that the accounts manager is not
# in the middle of something. Using a different file reference guarantees
# that the lock can only be grabbed once the accounts manager is done with
# it and holding it guarantees that the accounts manager won't start up
# again while shutting down.
logging.debug('Acquiring Daemon lock.')
lockfile = open(self.accounts_manager.lock_fname, 'r')
self.fcntl_module.flock(lockfile.fileno(), fcntl.LOCK_EX)
logging.debug('Shutting down Daemon module.')
# Clean up pidfile and terminate. Lock will be released with termination.
os.remove(self.pidfile)
exception = SystemExit('Terminating on signal number %d' % signal_number)
raise exception
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