OpenStack_Swift源代码分析——ObjectReplicator源代码分析(1)

1、ObjectorReplicator的启动

首先执行启动脚本

swift-init object-replicator start

此执行脚本的执行过程和ring执行脚本执行过程差点儿相同。找到swift 源代码bin下的swift-object-replicator其代码例如以下所看到的

if __name__ == '__main__':
    parser = OptionParser("%prog CONFIG [options]")
    parser.add_option('-d', '--devices',
                      help='Replicate only given devices. '
                           'Comma-separated list')
    parser.add_option('-p', '--partitions',
                      help='Replicate only given partitions. '
                           'Comma-separated list')
    conf_file, options = parse_options(parser=parser, once=True)
    run_daemon(ObjectReplicator, conf_file, **options)

最后一行：

 run_daemon(ObjectReplicator, conf_file, **options)

也就是要运行run_daemon()函数。为其传入的是ObjectReplicator和配置文件參数已经选项參数，以下继续看run_daemon方法。他是swift/daemon.py下Daemon类中的方法。看详细代码实现：

def run_daemon(klass, conf_file, section_name='', once=False, **kwargs):
    """
    Loads settings from conf, then instantiates daemon "klass" and runs the
    daemon with the specified once kwarg.  The section_name will be derived
    from the daemon "klass" if not provided (e.g. ObjectReplicator =>
    object-replicator).

    :param klass: Class to instantiate, subclass of common.daemon.Daemon
    :param conf_file: Path to configuration file
    :param section_name: Section name from conf file to load config from
    :param once: Passed to daemon run method
    """
    # very often the config section_name is based on the class name
    # the None singleton will be passed through to readconf as is
    if section_name is '':
        #得到section_name = ojbect-replicator  sub（）为正則表達式
        section_name = sub(r'([a-z])([A-Z])', r'\1-\2',
                           klass.__name__).lower()

    conf = utils.readconf(conf_file, section_name,
                          log_name=kwargs.get('log_name'))

    # once on command line (i.e. daemonize=false) will over-ride config
    once = once or not utils.config_true_value(conf.get('daemonize', 'true'))

    # pre-configure logger
    if 'logger' in kwargs:
        logger = kwargs.pop('logger')
    else:
        logger = utils.get_logger(conf, conf.get('log_name', section_name),
                                  log_to_console=kwargs.pop('verbose', False),
                                  log_route=section_name)

    # disable fallocate if desired
    if utils.config_true_value(conf.get('disable_fallocate', 'no')):
        utils.disable_fallocate()
    # set utils.FALLOCATE_RESERVE if desired
    reserve = int(conf.get('fallocate_reserve', 0))
    if reserve > 0:
        utils.FALLOCATE_RESERVE = reserve

    # By default, disable eventlet printing stacktraces
    eventlet_debug = utils.config_true_value(conf.get('eventlet_debug', 'no'))
    eventlet.debug.hub_exceptions(eventlet_debug)

    # Ensure TZ environment variable exists to avoid stat('/etc/localtime') on
    # some platforms. This locks in reported times to the timezone in which
    # the server first starts running in locations that periodically change
    # timezones.
    os.environ['TZ'] = time.strftime("%z", time.gmtime())

    try:
        #開始执行
        klass(conf).run(once=once, **kwargs)
    except KeyboardInterrupt:
        logger.info('User quit')
    logger.info('Exited')

因ObjectReplicator继承了Daemon类，代码片段

 klass(conf).run(once=once, **kwargs)

ObjectReplicator运行run方法，主要此时传入的once为False一般once在測试时能够设为True。

继续看run方法，在Objector中没有实现run方法，其继承了父类的方法，

    def run(self, once=False, **kwargs):
        """Run the daemon"""
        utils.validate_configuration()
        utils.drop_privileges(self.conf.get('user', 'swift'))
        utils.capture_stdio(self.logger, **kwargs)

        def kill_children(*args):
            #SIGTERM = 15  SIG_IGN = 1L
            signal.signal(signal.SIGTERM, signal.SIG_IGN)
            os.killpg(0, signal.SIGTERM)
            sys.exit()

        signal.signal(signal.SIGTERM, kill_children)
        if once:
            self.run_once(**kwargs)
        else:
            self.run_forever(**kwargs)

因once为False所以执行的是run_forever方法。从方法名字面上就能够看出这是一个永久执行的程序。也就是会成为守护进程。

  def run_forever(self, *args, **kwargs):
        self.logger.info(_("Starting object replicator in daemon mode."))
        # Run the replicator continually
        while True:
            start = time.time()
            self.logger.info(_("Starting object replication pass."))
            # Run the replicator
            #运行replicator 程序
            self.replicate()
            total = (time.time() - start) / 60
            self.logger.info(
                _("Object replication complete. (%.02f minutes)"), total)
            dump_recon_cache({'object_replication_time': total,
                              'object_replication_last': time.time()},
                             self.rcache, self.logger)
            self.logger.debug(_('Replication sleeping for %s seconds.'),
                              self.run_pause)
            #sleep 一段时间时间自己在部署时自己设定，也能够默觉得30秒
            sleep(self.run_pause)

在run_forever方法中会运行replicate（）方法。下一节介绍replicate方法的详细实现