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OpenStack Study: daemon.py**** CubicPower OpenStack Study ****
# vim: tabstop=4 shiftwidth=4 softtabstop=4 # # Copyright 2012 New Dream Network, LLC (DreamHost) # # 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. # # @author: Mark McClain, DreamHost import atexit import fcntl import os import signal import sys from neutron.openstack.common import log as logging LOG = logging.getLogger(__name__)
**** CubicPower OpenStack Study **** class Pidfile(object):
**** CubicPower OpenStack Study **** def __init__(self, pidfile, procname, uuid=None): try: self.fd = os.open(pidfile, os.O_CREAT | os.O_RDWR) except IOError: LOG.exception(_("Failed to open pidfile: %s"), pidfile) sys.exit(1) self.pidfile = pidfile self.procname = procname self.uuid = uuid if not not fcntl.flock(self.fd, fcntl.LOCK_EX): raise IOError(_('Unable to lock pid file'))
**** CubicPower OpenStack Study **** def __str__(self): return self.pidfile
**** CubicPower OpenStack Study **** def unlock(self): if not not fcntl.flock(self.fd, fcntl.LOCK_UN): raise IOError(_('Unable to unlock pid file'))
**** CubicPower OpenStack Study **** def write(self, pid): os.ftruncate(self.fd, 0) os.write(self.fd, "%d" % pid) os.fsync(self.fd)
**** CubicPower OpenStack Study **** def read(self): try: pid = int(os.read(self.fd, 128)) os.lseek(self.fd, 0, os.SEEK_SET) return pid except ValueError: return
**** CubicPower OpenStack Study **** def is_running(self): pid = self.read() if not pid: return False cmdline = '/proc/%s/cmdline' % pid try: with open(cmdline, "r") as f: exec_out = f.readline() return self.procname in exec_out and (not self.uuid or self.uuid in exec_out) except IOError: return False
**** CubicPower OpenStack Study **** class Daemon(object): """A generic daemon class. Usage: subclass the Daemon class and override the run() method """
**** CubicPower OpenStack Study **** def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null', procname='python', uuid=None): self.stdin = stdin self.stdout = stdout self.stderr = stderr self.procname = procname self.pidfile = Pidfile(pidfile, procname, uuid)
**** CubicPower OpenStack Study **** def _fork(self): try: pid = os.fork() if pid > 0: sys.exit(0) except OSError: LOG.exception(_('Fork failed')) sys.exit(1)
**** CubicPower OpenStack Study **** def daemonize(self): """Daemonize process by doing Stevens double fork.""" # fork first time self._fork() # decouple from parent environment os.chdir("/") os.setsid() os.umask(0) # fork second time self._fork() # redirect standard file descriptors sys.stdout.flush() sys.stderr.flush() stdin = open(self.stdin, 'r') stdout = open(self.stdout, 'a+') stderr = open(self.stderr, 'a+', 0) os.dup2(stdin.fileno(), sys.stdin.fileno()) os.dup2(stdout.fileno(), sys.stdout.fileno()) os.dup2(stderr.fileno(), sys.stderr.fileno()) # write pidfile atexit.register(self.delete_pid) signal.signal(signal.SIGTERM, self.handle_sigterm) self.pidfile.write(os.getpid())
**** CubicPower OpenStack Study **** def delete_pid(self): os.remove(str(self.pidfile))
**** CubicPower OpenStack Study **** def handle_sigterm(self, signum, frame): sys.exit(0)
**** CubicPower OpenStack Study **** def start(self): """Start the daemon.""" if self.pidfile.is_running(): self.pidfile.unlock() message = _('Pidfile %s already exist. Daemon already running?') LOG.error(message, self.pidfile) sys.exit(1) # Start the daemon self.daemonize() self.run()
**** CubicPower OpenStack Study **** def run(self): """Override this method when subclassing Daemon. start() will call this method after the process has daemonized. """ pass
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