OpenStack_Swift源码分析——ObjectReplicator源码分析(1)

1、ObjectorReplicator的启动

首先运行启动脚本

swift-init object-replicator start

此运行脚本的运行过程和ring运行脚本运行过程差不多，找到swift 源码bin下的swift-object-replicator其代码如下所示

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)

也就是要执行run_daemon()函数，为其传入的是ObjectReplicator和配置文件参数已经选项参数，下面继续看run_daemon方法，他是swift/daemon.py下Daemon类中的方法，看具体代码实现：

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（）为正则表达式
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:
#开始运行
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执行run方法，主要此时传入的once为False一般once在测试时可以设为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，从方法名字面上就可以看出这是一个永久运行的程序，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
#执行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，也可以默认为30秒
sleep(self.run_pause)

在run_forever方法中会执行replicate（）方法。下一节介绍replicate方法的具体实现