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OpenStack Study: service.py**** CubicPower OpenStack Study ****
# Copyright 2010 United States Government as represented by the # Administrator of the National Aeronautics and Space Administration. # Copyright 2011 Justin Santa Barbara # 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. """Generic Node base class for all workers that run on hosts.""" import errno import logging as std_logging import os import random import signal import sys import time try: # Importing just the symbol here because the io module does not # exist in Python 2.6. from io import UnsupportedOperation # noqa except ImportError: # Python 2.6 UnsupportedOperation = None import eventlet from eventlet import event from oslo.config import cfg from neutron.openstack.common import eventlet_backdoor from neutron.openstack.common.gettextutils import _ from neutron.openstack.common import importutils from neutron.openstack.common import log as logging from neutron.openstack.common import threadgroup rpc = importutils.try_import('neutron.openstack.common.rpc') CONF = cfg.CONF LOG = logging.getLogger(__name__)
**** CubicPower OpenStack Study **** def _sighup_supported(): return hasattr(signal, 'SIGHUP')
**** CubicPower OpenStack Study **** def _is_daemon(): # The process group for a foreground process will match the # process group of the controlling terminal. If those values do # not match, or ioctl() fails on the stdout file handle, we assume # the process is running in the background as a daemon. # http://www.gnu.org/software/bash/manual/bashref.html#Job-Control-Basics try: is_daemon = os.getpgrp() != os.tcgetpgrp(sys.stdout.fileno()) except OSError as err: if err.errno == errno.ENOTTY: # Assume we are a daemon because there is no terminal. is_daemon = True else: raise except UnsupportedOperation: # Could not get the fileno for stdout, so we must be a daemon. is_daemon = True return is_daemon
**** CubicPower OpenStack Study **** def _is_sighup_and_daemon(signo): if not (_sighup_supported() and signo == signal.SIGHUP): # Avoid checking if we are a daemon, because the signal isn't # SIGHUP. return False return _is_daemon()
**** CubicPower OpenStack Study **** def _signo_to_signame(signo): signals = {signal.SIGTERM: 'SIGTERM', signal.SIGINT: 'SIGINT'} if _sighup_supported(): signals[signal.SIGHUP] = 'SIGHUP' return signals[signo]
**** CubicPower OpenStack Study **** def _set_signals_handler(handler): signal.signal(signal.SIGTERM, handler) signal.signal(signal.SIGINT, handler) if _sighup_supported(): signal.signal(signal.SIGHUP, handler)
**** CubicPower OpenStack Study **** class Launcher(object): """Launch one or more services and wait for them to complete."""
**** CubicPower OpenStack Study **** def __init__(self): """Initialize the service launcher. :returns: None """ self.services = Services() self.backdoor_port = eventlet_backdoor.initialize_if_enabled()
**** CubicPower OpenStack Study **** def launch_service(self, service): """Load and start the given service. :param service: The service you would like to start. :returns: None """ service.backdoor_port = self.backdoor_port self.services.add(service)
**** CubicPower OpenStack Study **** def stop(self): """Stop all services which are currently running. :returns: None """ self.services.stop()
**** CubicPower OpenStack Study **** def wait(self): """Waits until all services have been stopped, and then returns. :returns: None """ self.services.wait()
**** CubicPower OpenStack Study **** def restart(self): """Reload config files and restart service. :returns: None """ cfg.CONF.reload_config_files() self.services.restart()
**** CubicPower OpenStack Study **** class SignalExit(SystemExit):
**** CubicPower OpenStack Study **** def __init__(self, signo, exccode=1): super(SignalExit, self).__init__(exccode) self.signo = signo
**** CubicPower OpenStack Study **** class ServiceLauncher(Launcher):
**** CubicPower OpenStack Study **** def _handle_signal(self, signo, frame): # Allow the process to be killed again and die from natural causes _set_signals_handler(signal.SIG_DFL) raise SignalExit(signo)
**** CubicPower OpenStack Study **** def handle_signal(self): _set_signals_handler(self._handle_signal)
**** CubicPower OpenStack Study **** def _wait_for_exit_or_signal(self, ready_callback=None): status = None signo = 0 LOG.debug(_('Full set of CONF:')) CONF.log_opt_values(LOG, std_logging.DEBUG) try: if ready_callback: ready_callback() super(ServiceLauncher, self).wait() except SignalExit as exc: signame = _signo_to_signame(exc.signo) LOG.info(_('Caught %s, exiting'), signame) status = exc.code signo = exc.signo except SystemExit as exc: status = exc.code finally: self.stop() if rpc: try: rpc.cleanup() except Exception: # We're shutting down, so it doesn't matter at this point. LOG.exception(_('Exception during rpc cleanup.')) return status, signo
**** CubicPower OpenStack Study **** def wait(self, ready_callback=None): while True: self.handle_signal() status, signo = self._wait_for_exit_or_signal(ready_callback) if not _is_sighup_and_daemon(signo): return status self.restart()
**** CubicPower OpenStack Study **** class ServiceWrapper(object):
**** CubicPower OpenStack Study **** def __init__(self, service, workers): self.service = service self.workers = workers self.children = set() self.forktimes = []
**** CubicPower OpenStack Study **** class ProcessLauncher(object):
**** CubicPower OpenStack Study **** def __init__(self, wait_interval=0.01): """Constructor. :param wait_interval: The interval to sleep for between checks of child process exit. """ self.children = {} self.sigcaught = None self.running = True self.wait_interval = wait_interval rfd, self.writepipe = os.pipe() self.readpipe = eventlet.greenio.GreenPipe(rfd, 'r') self.handle_signal()
**** CubicPower OpenStack Study **** def handle_signal(self): _set_signals_handler(self._handle_signal)
**** CubicPower OpenStack Study **** def _handle_signal(self, signo, frame): self.sigcaught = signo self.running = False # Allow the process to be killed again and die from natural causes _set_signals_handler(signal.SIG_DFL)
**** CubicPower OpenStack Study **** def _pipe_watcher(self): # This will block until the write end is closed when the parent # dies unexpectedly self.readpipe.read() LOG.info(_('Parent process has died unexpectedly, exiting')) sys.exit(1)
**** CubicPower OpenStack Study **** def _child_process_handle_signal(self): # Setup child signal handlers differently def _sigterm(*args): signal.signal(signal.SIGTERM, signal.SIG_DFL) raise SignalExit(signal.SIGTERM) def _sighup(*args): signal.signal(signal.SIGHUP, signal.SIG_DFL) raise SignalExit(signal.SIGHUP) signal.signal(signal.SIGTERM, _sigterm) if _sighup_supported(): signal.signal(signal.SIGHUP, _sighup) # Block SIGINT and let the parent send us a SIGTERM signal.signal(signal.SIGINT, signal.SIG_IGN)
**** CubicPower OpenStack Study **** def _sigterm(*args): signal.signal(signal.SIGTERM, signal.SIG_DFL) raise SignalExit(signal.SIGTERM)
**** CubicPower OpenStack Study **** def _sighup(*args): signal.signal(signal.SIGHUP, signal.SIG_DFL) raise SignalExit(signal.SIGHUP) signal.signal(signal.SIGTERM, _sigterm) if _sighup_supported(): signal.signal(signal.SIGHUP, _sighup) # Block SIGINT and let the parent send us a SIGTERM signal.signal(signal.SIGINT, signal.SIG_IGN)
**** CubicPower OpenStack Study **** def _child_wait_for_exit_or_signal(self, launcher): status = 0 signo = 0 # NOTE(johannes): All exceptions are caught to ensure this # doesn't fallback into the loop spawning children. It would # be bad for a child to spawn more children. try: launcher.wait() except SignalExit as exc: signame = _signo_to_signame(exc.signo) LOG.info(_('Caught %s, exiting'), signame) status = exc.code signo = exc.signo except SystemExit as exc: status = exc.code except BaseException: LOG.exception(_('Unhandled exception')) status = 2 finally: launcher.stop() return status, signo
**** CubicPower OpenStack Study **** def _child_process(self, service): self._child_process_handle_signal() # Reopen the eventlet hub to make sure we don't share an epoll # fd with parent and/or siblings, which would be bad eventlet.hubs.use_hub() # Close write to ensure only parent has it open os.close(self.writepipe) # Create greenthread to watch for parent to close pipe eventlet.spawn_n(self._pipe_watcher) # Reseed random number generator random.seed() launcher = Launcher() launcher.launch_service(service) return launcher
**** CubicPower OpenStack Study **** def _start_child(self, wrap): if len(wrap.forktimes) > wrap.workers: # Limit ourselves to one process a second (over the period of # number of workers * 1 second). This will allow workers to # start up quickly but ensure we don't fork off children that # die instantly too quickly. if time.time() - wrap.forktimes[0] < wrap.workers: LOG.info(_('Forking too fast, sleeping')) time.sleep(1) wrap.forktimes.pop(0) wrap.forktimes.append(time.time()) pid = os.fork() if pid == 0: launcher = self._child_process(wrap.service) while True: self._child_process_handle_signal() status, signo = self._child_wait_for_exit_or_signal(launcher) if not _is_sighup_and_daemon(signo): break launcher.restart() os._exit(status) LOG.info(_('Started child %d'), pid) wrap.children.add(pid) self.children[pid] = wrap return pid
**** CubicPower OpenStack Study **** def launch_service(self, service, workers=1): wrap = ServiceWrapper(service, workers) LOG.info(_('Starting %d workers'), wrap.workers) while self.running and len(wrap.children) < wrap.workers: self._start_child(wrap)
**** CubicPower OpenStack Study **** def _wait_child(self): try: # Don't block if no child processes have exited pid, status = os.waitpid(0, os.WNOHANG) if not pid: return None except OSError as exc: if exc.errno not in (errno.EINTR, errno.ECHILD): raise return None if os.WIFSIGNALED(status): sig = os.WTERMSIG(status) LOG.info(_('Child %(pid)d killed by signal %(sig)d'), dict(pid=pid, sig=sig)) else: code = os.WEXITSTATUS(status) LOG.info(_('Child %(pid)s exited with status %(code)d'), dict(pid=pid, code=code)) if pid not in self.children: LOG.warning(_('pid %d not in child list'), pid) return None wrap = self.children.pop(pid) wrap.children.remove(pid) return wrap
**** CubicPower OpenStack Study **** def _respawn_children(self): while self.running: wrap = self._wait_child() if not wrap: # Yield to other threads if no children have exited # Sleep for a short time to avoid excessive CPU usage # (see bug #1095346) eventlet.greenthread.sleep(self.wait_interval) continue while self.running and len(wrap.children) < wrap.workers: self._start_child(wrap)
**** CubicPower OpenStack Study **** def wait(self): """Loop waiting on children to die and respawning as necessary.""" LOG.debug(_('Full set of CONF:')) CONF.log_opt_values(LOG, std_logging.DEBUG) while True: self.handle_signal() self._respawn_children() if self.sigcaught: signame = _signo_to_signame(self.sigcaught) LOG.info(_('Caught %s, stopping children'), signame) if not _is_sighup_and_daemon(self.sigcaught): break for pid in self.children: os.kill(pid, signal.SIGHUP) self.running = True self.sigcaught = None for pid in self.children: try: os.kill(pid, signal.SIGTERM) except OSError as exc: if exc.errno != errno.ESRCH: raise # Wait for children to die if self.children: LOG.info(_('Waiting on %d children to exit'), len(self.children)) while self.children: self._wait_child()
**** CubicPower OpenStack Study **** class Service(object): """Service object for binaries running on hosts."""
**** CubicPower OpenStack Study **** def __init__(self, threads=1000): self.tg = threadgroup.ThreadGroup(threads) # signal that the service is done shutting itself down: self._done = event.Event()
**** CubicPower OpenStack Study **** def reset(self): # NOTE(Fengqian): docs for Event.reset() recommend against using it self._done = event.Event()
**** CubicPower OpenStack Study **** def start(self): pass
**** CubicPower OpenStack Study **** def stop(self): self.tg.stop() self.tg.wait() # Signal that service cleanup is done: if not self._done.ready(): self._done.send()
**** CubicPower OpenStack Study **** def wait(self): self._done.wait()
**** CubicPower OpenStack Study **** class Services(object):
**** CubicPower OpenStack Study **** def __init__(self): self.services = [] self.tg = threadgroup.ThreadGroup() self.done = event.Event()
**** CubicPower OpenStack Study **** def add(self, service): self.services.append(service) self.tg.add_thread(self.run_service, service, self.done)
**** CubicPower OpenStack Study **** def stop(self): # wait for graceful shutdown of services: for service in self.services: service.stop() service.wait() # Each service has performed cleanup, now signal that the run_service # wrapper threads can now die: if not self.done.ready(): self.done.send() # reap threads: self.tg.stop()
**** CubicPower OpenStack Study **** def wait(self): self.tg.wait()
**** CubicPower OpenStack Study **** def restart(self): self.stop() self.done = event.Event() for restart_service in self.services: restart_service.reset() self.tg.add_thread(self.run_service, restart_service, self.done) @staticmethod
**** CubicPower OpenStack Study **** def run_service(service, done): """Service start wrapper. :param service: service to run :param done: event to wait on until a shutdown is triggered :returns: None """ service.start() done.wait() def launch(service, workers=None): if workers: launcher = ProcessLauncher() launcher.launch_service(service, workers=workers) else: launcher = ServiceLauncher() launcher.launch_service(service) return launcher
**** CubicPower OpenStack Study **** def launch(service, workers=None): if workers: launcher = ProcessLauncher() launcher.launch_service(service, workers=workers) else: launcher = ServiceLauncher() launcher.launch_service(service) return launcher
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