150 lines
4.2 KiB
Python
150 lines
4.2 KiB
Python
# Copyright 2012 New Dream Network, LLC (DreamHost)
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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#
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# @author: Mark McClain, DreamHost
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import atexit
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import fcntl
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import os
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import signal
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import sys
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from neutron.openstack.common import log as logging
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LOG = logging.getLogger(__name__)
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class Pidfile(object):
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def __init__(self, pidfile, procname, uuid=None):
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self.pidfile = pidfile
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self.procname = procname
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self.uuid = uuid
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try:
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self.fd = os.open(pidfile, os.O_CREAT | os.O_RDWR)
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fcntl.flock(self.fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except IOError:
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LOG.exception(_("Error while handling pidfile: %s"), pidfile)
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sys.exit(1)
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def __str__(self):
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return self.pidfile
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def unlock(self):
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if not not fcntl.flock(self.fd, fcntl.LOCK_UN):
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raise IOError(_('Unable to unlock pid file'))
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def write(self, pid):
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os.ftruncate(self.fd, 0)
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os.write(self.fd, "%d" % pid)
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os.fsync(self.fd)
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def read(self):
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try:
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pid = int(os.read(self.fd, 128))
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os.lseek(self.fd, 0, os.SEEK_SET)
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return pid
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except ValueError:
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return
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def is_running(self):
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pid = self.read()
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if not pid:
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return False
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cmdline = '/proc/%s/cmdline' % pid
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try:
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with open(cmdline, "r") as f:
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exec_out = f.readline()
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return self.procname in exec_out and (not self.uuid or
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self.uuid in exec_out)
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except IOError:
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return False
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class Daemon(object):
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"""A generic daemon class.
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Usage: subclass the Daemon class and override the run() method
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"""
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def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null',
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stderr='/dev/null', procname='python', uuid=None):
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self.stdin = stdin
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self.stdout = stdout
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self.stderr = stderr
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self.procname = procname
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self.pidfile = Pidfile(pidfile, procname, uuid)
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def _fork(self):
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try:
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pid = os.fork()
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if pid > 0:
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sys.exit(0)
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except OSError:
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LOG.exception(_('Fork failed'))
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sys.exit(1)
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def daemonize(self):
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"""Daemonize process by doing Stevens double fork."""
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# fork first time
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self._fork()
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# decouple from parent environment
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os.chdir("/")
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os.setsid()
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os.umask(0)
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# fork second time
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self._fork()
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# redirect standard file descriptors
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sys.stdout.flush()
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sys.stderr.flush()
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stdin = open(self.stdin, 'r')
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stdout = open(self.stdout, 'a+')
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stderr = open(self.stderr, 'a+', 0)
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os.dup2(stdin.fileno(), sys.stdin.fileno())
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os.dup2(stdout.fileno(), sys.stdout.fileno())
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os.dup2(stderr.fileno(), sys.stderr.fileno())
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# write pidfile
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atexit.register(self.delete_pid)
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signal.signal(signal.SIGTERM, self.handle_sigterm)
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self.pidfile.write(os.getpid())
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def delete_pid(self):
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os.remove(str(self.pidfile))
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def handle_sigterm(self, signum, frame):
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sys.exit(0)
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def start(self):
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"""Start the daemon."""
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if self.pidfile.is_running():
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self.pidfile.unlock()
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message = _('Pidfile %s already exist. Daemon already running?')
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LOG.error(message, self.pidfile)
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sys.exit(1)
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# Start the daemon
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self.daemonize()
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self.run()
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def run(self):
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"""Override this method when subclassing Daemon.
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start() will call this method after the process has daemonized.
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"""
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pass
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