508 lines
15 KiB
Python
508 lines
15 KiB
Python
# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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# Copyright 2011 Justin Santa Barbara
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# All Rights Reserved.
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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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"""Generic Node base class for all workers that run on hosts."""
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import errno
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import io
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import logging
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import os
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import random
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import signal
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import sys
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import time
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import eventlet
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from eventlet import event
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from oslo_config import cfg
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from neutron.openstack.common import eventlet_backdoor
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from neutron.openstack.common._i18n import _LE, _LI, _LW
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from neutron.openstack.common import systemd
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from neutron.openstack.common import threadgroup
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CONF = cfg.CONF
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LOG = logging.getLogger(__name__)
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def _sighup_supported():
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return hasattr(signal, 'SIGHUP')
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def _is_daemon():
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# The process group for a foreground process will match the
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# process group of the controlling terminal. If those values do
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# not match, or ioctl() fails on the stdout file handle, we assume
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# the process is running in the background as a daemon.
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# http://www.gnu.org/software/bash/manual/bashref.html#Job-Control-Basics
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try:
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is_daemon = os.getpgrp() != os.tcgetpgrp(sys.stdout.fileno())
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except io.UnsupportedOperation:
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# Could not get the fileno for stdout, so we must be a daemon.
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is_daemon = True
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except OSError as err:
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if err.errno == errno.ENOTTY:
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# Assume we are a daemon because there is no terminal.
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is_daemon = True
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else:
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raise
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return is_daemon
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def _is_sighup_and_daemon(signo):
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if not (_sighup_supported() and signo == signal.SIGHUP):
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# Avoid checking if we are a daemon, because the signal isn't
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# SIGHUP.
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return False
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return _is_daemon()
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def _signo_to_signame(signo):
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signals = {signal.SIGTERM: 'SIGTERM',
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signal.SIGINT: 'SIGINT'}
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if _sighup_supported():
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signals[signal.SIGHUP] = 'SIGHUP'
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return signals[signo]
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def _set_signals_handler(handler):
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signal.signal(signal.SIGTERM, handler)
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signal.signal(signal.SIGINT, handler)
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if _sighup_supported():
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signal.signal(signal.SIGHUP, handler)
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class Launcher(object):
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"""Launch one or more services and wait for them to complete."""
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def __init__(self):
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"""Initialize the service launcher.
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:returns: None
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"""
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self.services = Services()
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self.backdoor_port = eventlet_backdoor.initialize_if_enabled()
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def launch_service(self, service):
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"""Load and start the given service.
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:param service: The service you would like to start.
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:returns: None
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"""
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service.backdoor_port = self.backdoor_port
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self.services.add(service)
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def stop(self):
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"""Stop all services which are currently running.
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:returns: None
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"""
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self.services.stop()
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def wait(self):
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"""Waits until all services have been stopped, and then returns.
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:returns: None
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"""
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self.services.wait()
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def restart(self):
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"""Reload config files and restart service.
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:returns: None
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"""
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cfg.CONF.reload_config_files()
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self.services.restart()
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class SignalExit(SystemExit):
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def __init__(self, signo, exccode=1):
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super(SignalExit, self).__init__(exccode)
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self.signo = signo
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class ServiceLauncher(Launcher):
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def _handle_signal(self, signo, frame):
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# Allow the process to be killed again and die from natural causes
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_set_signals_handler(signal.SIG_DFL)
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raise SignalExit(signo)
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def handle_signal(self):
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_set_signals_handler(self._handle_signal)
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def _wait_for_exit_or_signal(self, ready_callback=None):
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status = None
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signo = 0
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LOG.debug('Full set of CONF:')
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CONF.log_opt_values(LOG, logging.DEBUG)
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try:
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if ready_callback:
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ready_callback()
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super(ServiceLauncher, self).wait()
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except SignalExit as exc:
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signame = _signo_to_signame(exc.signo)
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LOG.info(_LI('Caught %s, exiting'), signame)
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status = exc.code
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signo = exc.signo
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except SystemExit as exc:
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status = exc.code
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finally:
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self.stop()
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return status, signo
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def wait(self, ready_callback=None):
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systemd.notify_once()
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while True:
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self.handle_signal()
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status, signo = self._wait_for_exit_or_signal(ready_callback)
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if not _is_sighup_and_daemon(signo):
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return status
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self.restart()
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class ServiceWrapper(object):
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def __init__(self, service, workers):
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self.service = service
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self.workers = workers
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self.children = set()
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self.forktimes = []
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class ProcessLauncher(object):
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_signal_handlers_set = set()
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@classmethod
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def _handle_class_signals(cls, *args, **kwargs):
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for handler in cls._signal_handlers_set:
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handler(*args, **kwargs)
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def __init__(self, wait_interval=0.01):
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"""Constructor.
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:param wait_interval: The interval to sleep for between checks
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of child process exit.
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"""
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self.children = {}
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self.sigcaught = None
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self.running = True
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self.wait_interval = wait_interval
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rfd, self.writepipe = os.pipe()
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self.readpipe = eventlet.greenio.GreenPipe(rfd, 'r')
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self.handle_signal()
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def handle_signal(self):
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self._signal_handlers_set.add(self._handle_signal)
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_set_signals_handler(self._handle_class_signals)
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def _handle_signal(self, signo, frame):
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self.sigcaught = signo
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self.running = False
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# Allow the process to be killed again and die from natural causes
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_set_signals_handler(signal.SIG_DFL)
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def _pipe_watcher(self):
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# This will block until the write end is closed when the parent
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# dies unexpectedly
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self.readpipe.read(1)
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LOG.info(_LI('Parent process has died unexpectedly, exiting'))
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sys.exit(1)
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def _child_process_handle_signal(self):
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# Setup child signal handlers differently
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def _sighup(*args):
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signal.signal(signal.SIGHUP, signal.SIG_DFL)
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raise SignalExit(signal.SIGHUP)
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# Parent signals with SIGTERM when it wants us to go away.
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signal.signal(signal.SIGTERM, signal.SIG_DFL)
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if _sighup_supported():
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signal.signal(signal.SIGHUP, _sighup)
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# Block SIGINT and let the parent send us a SIGTERM
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signal.signal(signal.SIGINT, signal.SIG_IGN)
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def _child_wait_for_exit_or_signal(self, launcher):
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status = 0
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signo = 0
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# NOTE(johannes): All exceptions are caught to ensure this
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# doesn't fallback into the loop spawning children. It would
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# be bad for a child to spawn more children.
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try:
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launcher.wait()
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except SignalExit as exc:
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signame = _signo_to_signame(exc.signo)
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LOG.info(_LI('Child caught %s, exiting'), signame)
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status = exc.code
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signo = exc.signo
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except SystemExit as exc:
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status = exc.code
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except BaseException:
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LOG.exception(_LE('Unhandled exception'))
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status = 2
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finally:
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launcher.stop()
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return status, signo
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def _child_process(self, service):
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self._child_process_handle_signal()
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# Reopen the eventlet hub to make sure we don't share an epoll
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# fd with parent and/or siblings, which would be bad
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eventlet.hubs.use_hub()
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# Close write to ensure only parent has it open
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os.close(self.writepipe)
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# Create greenthread to watch for parent to close pipe
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eventlet.spawn_n(self._pipe_watcher)
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# Reseed random number generator
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random.seed()
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launcher = Launcher()
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launcher.launch_service(service)
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return launcher
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def _start_child(self, wrap):
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if len(wrap.forktimes) > wrap.workers:
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# Limit ourselves to one process a second (over the period of
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# number of workers * 1 second). This will allow workers to
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# start up quickly but ensure we don't fork off children that
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# die instantly too quickly.
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if time.time() - wrap.forktimes[0] < wrap.workers:
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LOG.info(_LI('Forking too fast, sleeping'))
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time.sleep(1)
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wrap.forktimes.pop(0)
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wrap.forktimes.append(time.time())
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pid = os.fork()
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if pid == 0:
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launcher = self._child_process(wrap.service)
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while True:
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self._child_process_handle_signal()
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status, signo = self._child_wait_for_exit_or_signal(launcher)
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if not _is_sighup_and_daemon(signo):
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break
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launcher.restart()
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os._exit(status)
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LOG.info(_LI('Started child %d'), pid)
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wrap.children.add(pid)
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self.children[pid] = wrap
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return pid
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def launch_service(self, service, workers=1):
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wrap = ServiceWrapper(service, workers)
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LOG.info(_LI('Starting %d workers'), wrap.workers)
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while self.running and len(wrap.children) < wrap.workers:
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self._start_child(wrap)
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def _wait_child(self):
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try:
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# Don't block if no child processes have exited
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pid, status = os.waitpid(0, os.WNOHANG)
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if not pid:
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return None
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except OSError as exc:
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if exc.errno not in (errno.EINTR, errno.ECHILD):
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raise
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return None
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if os.WIFSIGNALED(status):
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sig = os.WTERMSIG(status)
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LOG.info(_LI('Child %(pid)d killed by signal %(sig)d'),
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dict(pid=pid, sig=sig))
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else:
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code = os.WEXITSTATUS(status)
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LOG.info(_LI('Child %(pid)s exited with status %(code)d'),
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dict(pid=pid, code=code))
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if pid not in self.children:
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LOG.warning(_LW('pid %d not in child list'), pid)
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return None
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wrap = self.children.pop(pid)
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wrap.children.remove(pid)
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return wrap
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def _respawn_children(self):
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while self.running:
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wrap = self._wait_child()
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if not wrap:
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# Yield to other threads if no children have exited
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# Sleep for a short time to avoid excessive CPU usage
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# (see bug #1095346)
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eventlet.greenthread.sleep(self.wait_interval)
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continue
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while self.running and len(wrap.children) < wrap.workers:
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self._start_child(wrap)
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def wait(self):
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"""Loop waiting on children to die and respawning as necessary."""
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systemd.notify_once()
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LOG.debug('Full set of CONF:')
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CONF.log_opt_values(LOG, logging.DEBUG)
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try:
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while True:
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self.handle_signal()
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self._respawn_children()
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# No signal means that stop was called. Don't clean up here.
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if not self.sigcaught:
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return
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signame = _signo_to_signame(self.sigcaught)
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LOG.info(_LI('Caught %s, stopping children'), signame)
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if not _is_sighup_and_daemon(self.sigcaught):
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break
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cfg.CONF.reload_config_files()
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for service in set(
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[wrap.service for wrap in self.children.values()]):
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service.reset()
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for pid in self.children:
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os.kill(pid, signal.SIGHUP)
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self.running = True
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self.sigcaught = None
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except eventlet.greenlet.GreenletExit:
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LOG.info(_LI("Wait called after thread killed. Cleaning up."))
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self.stop()
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def stop(self):
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"""Terminate child processes and wait on each."""
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self.running = False
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for pid in self.children:
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try:
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os.kill(pid, signal.SIGTERM)
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except OSError as exc:
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if exc.errno != errno.ESRCH:
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raise
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# Wait for children to die
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if self.children:
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LOG.info(_LI('Waiting on %d children to exit'), len(self.children))
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while self.children:
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self._wait_child()
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class Service(object):
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"""Service object for binaries running on hosts."""
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def __init__(self, threads=1000):
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self.tg = threadgroup.ThreadGroup(threads)
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# signal that the service is done shutting itself down:
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self._done = event.Event()
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def reset(self):
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# NOTE(Fengqian): docs for Event.reset() recommend against using it
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self._done = event.Event()
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def start(self):
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pass
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def stop(self, graceful=False):
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self.tg.stop(graceful)
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self.tg.wait()
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# Signal that service cleanup is done:
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if not self._done.ready():
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self._done.send()
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def wait(self):
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self._done.wait()
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class Services(object):
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def __init__(self):
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self.services = []
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self.tg = threadgroup.ThreadGroup()
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self.done = event.Event()
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def add(self, service):
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self.services.append(service)
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self.tg.add_thread(self.run_service, service, self.done)
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def stop(self):
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# wait for graceful shutdown of services:
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for service in self.services:
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service.stop()
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service.wait()
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# Each service has performed cleanup, now signal that the run_service
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# wrapper threads can now die:
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if not self.done.ready():
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self.done.send()
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# reap threads:
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self.tg.stop()
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def wait(self):
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self.tg.wait()
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def restart(self):
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self.stop()
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self.done = event.Event()
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for restart_service in self.services:
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restart_service.reset()
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self.tg.add_thread(self.run_service, restart_service, self.done)
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@staticmethod
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def run_service(service, done):
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"""Service start wrapper.
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:param service: service to run
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:param done: event to wait on until a shutdown is triggered
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:returns: None
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"""
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service.start()
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done.wait()
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def launch(service, workers=1):
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if workers is None or workers == 1:
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launcher = ServiceLauncher()
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launcher.launch_service(service)
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else:
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launcher = ProcessLauncher()
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launcher.launch_service(service, workers=workers)
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return launcher
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