OpenStack Networking (Neutron)
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neutron/neutron/agent/linux/daemon.py

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4.2 KiB

# 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__)
class Pidfile(object):
def __init__(self, pidfile, procname, uuid=None):
self.pidfile = pidfile
self.procname = procname
self.uuid = uuid
try:
self.fd = os.open(pidfile, os.O_CREAT | os.O_RDWR)
fcntl.flock(self.fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
except IOError:
LOG.exception(_("Error while handling pidfile: %s"), pidfile)
sys.exit(1)
def __str__(self):
return self.pidfile
def unlock(self):
if not not fcntl.flock(self.fd, fcntl.LOCK_UN):
raise IOError(_('Unable to unlock pid file'))
def write(self, pid):
os.ftruncate(self.fd, 0)
os.write(self.fd, "%d" % pid)
os.fsync(self.fd)
def read(self):
try:
pid = int(os.read(self.fd, 128))
os.lseek(self.fd, 0, os.SEEK_SET)
return pid
except ValueError:
return
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
class Daemon(object):
"""A generic daemon class.
Usage: subclass the Daemon class and override the run() method
"""
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)
def _fork(self):
try:
pid = os.fork()
if pid > 0:
sys.exit(0)
except OSError:
LOG.exception(_('Fork failed'))
sys.exit(1)
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())
def delete_pid(self):
os.remove(str(self.pidfile))
def handle_sigterm(self, signum, frame):
sys.exit(0)
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()
def run(self):
"""Override this method when subclassing Daemon.
start() will call this method after the process has daemonized.
"""
pass