nova service的heatbeat机制

nova conductor这个服务启动的入口函数在nova/cmd/conductor.py 中，我们重点关注heatbeat服务
def main()://调用service的构造函数，其位于nova/service.py中server = service.Service.create(binary='nova-conductor',topic=CONF.conductor.topic,manager=CONF.conductor.manager)workers = CONF.conductor.workers or processutils.get_worker_count()service.serve(server, workers=workers)service.wait()
service的构造函数class Service(service.Service):"""Service object for binaries running on hosts.A service takes a manager and enables rpc by listening to queues basedon topic. It also periodically runs tasks on the manager and reportsits state to the database services table."""def __init__(self, host, binary, topic, manager, report_interval=None,periodic_enable=None, periodic_fuzzy_delay=None,periodic_interval_max=None, db_allowed=True,*args, **kwargs):super(Service, self).__init__()self.host = hostself.binary = binaryself.topic = topicself.manager_class_name = manager
//调用servicegroupself.servicegroup_api = servicegroup.API()servicegroup的函数位于nova/servicegroup/api.py 中，最终调用join函数
class API(object):def join(self, member, group, service=None):"""Add a new member to a service group.:param member: the joined member ID/name:param group: the group ID/name, of the joined member:param service: a `nova.service.Service` object"""return self._driver.join(member, group, service)
在service中发现有两种调用数据库的方法，这里我们采用的是mysql，因此我们用的是db
_driver_name_class_mapping = {'db': 'nova.servicegroup.drivers.db.DbDriver','mc': 'nova.servicegroup.drivers.mc.MemcachedDriver'
}
所以driver的join函数最终是在nova/servicegroup/drivers/db.py 中实现的
class DbDriver(base.Driver):def __init__(self, *args, **kwargs):self.service_down_time = CONF.service_down_timedef join(self, member, group, service=None):"""Add a new member to a service group.:param member: the joined member ID/name:param group: the group ID/name, of the joined member:param service: a `nova.service.Service` object"""LOG.debug('DB_Driver: join new ServiceGroup member %(member)s to ''the %(group)s group, service = %(service)s',{'member': member, 'group': group,'service': service})if service is None:raise RuntimeError(_('service is a mandatory argument for DB based'' ServiceGroup driver'))report_interval = service.report_intervalif report_interval:
核心代码可见是注册了一个time来定时调用_report_stateservice.tg.add_timer(report_interval, self._report_state,api.INITIAL_REPORTING_DELAY, service)
其中_report_state 同样在nova/servicegroup/drivers/db.py 中实现def _report_state(self, service):"""Update the state of this service in the datastore."""try:
可见heatbeat的最终实现就是从db中读到report_count然后自加后在保存回去service.service_ref.report_count += 1service.service_ref.save()# TODO(termie): make this pattern be more elegant.if getattr(service, 'model_disconnected', False):service.model_disconnected = FalseLOG.info(_LI('Recovered from being unable to report status.'))except messaging.MessagingTimeout:# NOTE(johngarbutt) during upgrade we will see messaging timeouts# as nova-conductor is restarted, so only log this error once.if not getattr(service, 'model_disconnected', False):service.model_disconnected = TrueLOG.warning(_LW('Lost connection to nova-conductor ''for reporting service status.'))通过在nova/servicegroup/drivers/db.py 中实现了检查服务是否up的函数def is_up(self, service_ref):"""Moved from nova.utilsCheck whether a service is up based on last heartbeat."""# Keep checking 'updated_at' if 'last_seen_up' isn't set.# Should be able to use only 'last_seen_up' in the M releaselast_heartbeat = (service_ref.get('last_seen_up') orservice_ref['updated_at'] or service_ref['created_at'])if isinstance(last_heartbeat, six.string_types):# NOTE(russellb) If this service_ref came in over rpc via# conductor, then the timestamp will be a string and needs to be# converted back to a datetime.last_heartbeat = timeutils.parse_strtime(last_heartbeat)else:# Objects have proper UTC timezones, but the timeutils comparison# below does not (and will fail)last_heartbeat = last_heartbeat.replace(tzinfo=None)# Timestamps in DB are UTC.elapsed = timeutils.delta_seconds(last_heartbeat, timeutils.utcnow())
可见是否up的判断条件是否两次heatbeat的时间是否小于service_down_time。而这个之是在init函数中通过配置文件读到的self.service_down_time = CONF.service_down_timeis_up = abs(elapsed) <= self.service_down_timeif not is_up:LOG.debug('Seems service %(binary)s on host %(host)s is down. ''Last heartbeat was %(lhb)s. Elapsed time is %(el)s',{'binary': service_ref.get('binary'),'host': service_ref.get('host'),'lhb': str(last_heartbeat), 'el': str(elapsed)})return is_up这样当通过nova service-list 来查询服务是否up是回调到nova/api/openstack/compute/services.pylass ServiceController(wsgi.Controller):def _get_service_detail(self, svc, additional_fields):
//service_is_up 最终会调到前面说的db中的servicegroup/api.py 中的service_is_upalive = self.servicegroup_api.service_is_up(svc)state = (alive and "up") or "down"active = 'enabled'if svc['disabled']:active = 'disabled'service_detail = {'binary': svc['binary'],'host': svc['host'],'id': svc['id'],'zone': svc['availability_zone'],'status': active,'state': state,'updated_at': svc['updated_at'],'disabled_reason': svc['disabled_reason']}for field in additional_fields:service_detail[field] = svc[field]return service_detailservice_is_up 源码如下，可见最终会调用到前面将的db中的is_up来判断service是否updef service_is_up(self, member):"""Check if the given member is up."""# NOTE(johngarbutt) no logging in this method,# so this doesn't slow down the schedulerif member.get('forced_down'):return Falsereturn self._driver.is_up(member)

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