基于ocata版本的，源码梳理
1)用户输入cinder service-list命令行，查看cinder服务的状态时，cinder的入口函数为cinder/api/contrib/services.py:Service:index方法
class ServiceController(wsgi.Controller):
def __init__(self, ext_mgr=None):
self.ext_mgr = ext_mgr
super(ServiceController, self).__init__()
self.volume_api = volume.API()
def index(self, req):
"""Return a list of all running services.
Filter by host & service name.
"""
context = req.environ['cinder.context']
authorize(context, action='index')
detailed = self.ext_mgr.is_loaded('os-extended-services')
now = timeutils.utcnow(with_timezone=True)------------------//获取controller 当前的时间
filters = {}
if 'host' in req.GET:
filters['host'] = req.GET['host']
if 'binary' in req.GET:
filters['binary'] = req.GET['binary']
elif 'service' in req.GET:
filters['binary'] = req.GET['service']
versionutils.report_deprecated_feature(LOG, _(
"Query by service parameter is deprecated. "
"Please use binary parameter instead."))
services = objects.ServiceList.get_all(context, filters)----------//从 db 获取所有的 cinder service 列表
svcs = []
for svc in services:----------------------------//循环每个 service
updated_at = svc.updated_at
delta = now - (svc.updated_at or svc.created_at)-------------//获取 updated_at。不存在的话，获取 created_at，并和当前时间计算时间差
delta_sec = delta.total_seconds()
if svc.modified_at:
delta_mod = now - svc.modified_at
if abs(delta_sec) >= abs(delta_mod.total_seconds()):
updated_at = svc.modified_at
alive = abs(delta_sec) <= CONF.service_down_time------/获取时间差值的绝对值，并检查是否小于配置的 server_down_time，该配置项默认是60秒
art = (alive and "up") or "down"----------------------//如果差值小于60，则service 状态为 up，否则为 down
active = 'enabled'
if svc.disabled:
active = 'disabled'
if updated_at:
updated_at = timeutils.normalize_time(updated_at)
ret_fields = {'binary': svc.binary, 'host': svc.host,
'zone': svc.availability_zone,
'status': active, 'state': art,
'updated_at': updated_at}
# On V3.7 we added cluster support
if req.api_version_request.matches('3.7'):
ret_fields['cluster'] = svc.cluster_name
if detailed:
ret_fields['disabled_reason'] = svc.disabled_reason
if svc.binary == "cinder-volume":
ret_fields['replication_status'] = svc.replication_status
ret_fields['active_backend_id'] = svc.active_backend_id
ret_fields['frozen'] = svc.frozen
svcs.append(ret_fields)
return {'services': svcs}
因此 service 的 up/down 状态取决于数据库中 service 表对应某 service 的行的 updated_at 列的值和当前 controller 节点的时间的差值是否在配置的范围之内，如果差值在设置的范围之内，那么就认为服务是up的，如果差值不在设置的范围之内，那么就认为服务时down的，那么每个服务的updated_at的值从如何更新的？
2、cinder各个服务对应数据库中update_at值的更新，这个字段的时间值，获取的是该服务运行在哪个物理节点上，就获取当前物理节点的时间值，更新到数据库值，计数器加1
cinder 的各种service，比如cinder-api，cinder-backup 等，都是cinder/service.py 文件中 class Service(service.Service) 的一个实例
(这个实例，采用一个manager,使能rpc，通过监听基于topic的队列，同时他还定期在manager上运行一个任务，上报他的状态给数据库服务表)
该类的start方法如下：
def start(self):
version_string = version.version_string()
LOG.info(_LI('Starting %(topic)s node (version %(version_string)s)'),
{'topic': self.topic, 'version_string': version_string})
self.model_disconnected = False
if self.coordination:
coordination.COORDINATOR.start()
self.manager.init_host(added_to_cluster=self.added_to_cluster,--------调用的是manager模块中init_host方法，
service_id=Service.service_id)------------------这个方法的实现中依次调用driver.do_setup,driver.check_for_setup_error,driver.init_capabilities 三个函数，而函数init_capabilities中有会调动驱动的get_volume_stats函数来获取存储后端的存储状态信息
LOG.debug("Creating RPC server for service %s", self.topic)
ctxt = context.get_admin_context()
endpoints = [self.manager]
endpoints.extend(self.manager.additional_endpoints)
obj_version_cap = objects.Service.get_minimum_obj_version(ctxt)
LOG.debug("Pinning object versions for RPC server serializer to %s",
obj_version_cap)
serializer = objects_base.CinderObjectSerializer(obj_version_cap)
target = messaging.Target(topic=self.topic, server=self.host)
self.rpcserver = rpc.get_server(target, endpoints, serializer)
self.rpcserver.start()
# NOTE(dulek): Kids, don't do that at home. We're relying here on
# oslo.messaging implementation details to keep backward compatibility
# with pre-Ocata services. This will not matter once we drop
# compatibility with them.
if self.topic == constants.VOLUME_TOPIC:
target = messaging.Target(
topic='%(topic)s.%(host)s' % {'topic': self.topic,
'host': self.host},
server=vol_utils.extract_host(self.host, 'host'))
self.backend_rpcserver = rpc.get_server(target, endpoints,
serializer)
self.backend_rpcserver.start()
# TODO(geguileo): In O - Remove the is_svc_upgrading_to_n part
if self.cluster and not self.is_svc_upgrading_to_n(self.binary):
LOG.info(_LI('Starting %(topic)s cluster %(cluster)s (version '
'%(version)s)'),
{'topic': self.topic, 'version': version_string,
'cluster': self.cluster})
target = messaging.Target(
topic='%s.%s' % (self.topic, self.cluster),
server=vol_utils.extract_host(self.cluster, 'host'))
serializer = objects_base.CinderObjectSerializer(obj_version_cap)
self.cluster_rpcserver = rpc.get_server(target, endpoints,
serializer)
self.cluster_rpcserver.start()
self.manager.init_host_with_rpc()
if self.report_interval:-------------------------//如果设置了 report_interval 配置项，那么该 service 将启动一个无限循环来执行 report_state 方法，
运行间隔就是 report_interval，其默认值是 10 秒，即默认10上报一次状态
pulse = loopingcall.FixedIntervalLoopingCall(----------这是一个循环，self.report_state这个方法就是要循环执行的任务
self.report_state)
pulse.start(interval=self.report_interval,-----------开始这个运行这个循环，s1
initial_delay=self.report_interval)
self.timers.append(pulse)
if self.periodic_interval:
if self.periodic_fuzzy_delay:
initial_delay = random.randint(0, self.periodic_fuzzy_delay)
else:
initial_delay = None
periodic = loopingcall.FixedIntervalLoopingCall(
self.periodic_tasks)
periodic.start(interval=self.periodic_interval,
initial_delay=initial_delay)
self.timers.append(periodic)
s1方法的实现
def report_state(self):----更新服务的状态到数据库中
"""Update the state of this service in the datastore."""
if not self.manager.is_working():
# NOTE(dulek): If manager reports a problem we're not sending
# heartbeats - to indicate that service is actually down.
LOG.error(_LE('Manager for service %(binary)s %(host)s is '
'reporting problems, not sending heartbeat. '
'Service will appear "down".'),
{'binary': self.binary,
'host': self.host})
return
ctxt = context.get_admin_context()
zone = CONF.storage_availability_zone
try:
try:
service_ref = objects.Service.get_by_id(ctxt,Service.service_id)-----根据service_id从数据库中获取service信息
except exception.NotFound:
LOG.debug('The service database object disappeared, '
'recreating it.')
self._create_service_ref(ctxt)
service_ref = objects.Service.get_by_id(ctxt,Service.service_id)
service_ref.report_count += 1--------------更新报告计数器，加1
if zone != service_ref.availability_zone:
service_ref.availability_zone = zone
service_ref.save()
# TODO(termie): make this pattern be more elegant.
if getattr(self, 'model_disconnected', False):
self.model_disconnected = False
LOG.error(_LE('Recovered model server connection!'))
3、services表字段的内容
mysql> desc services; +------------------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------------+--------------+------+-----+---------+----------------+ | created_at | datetime | YES | | NULL | | | updated_at | datetime | YES | | NULL | | | deleted_at | datetime | YES | | NULL | | | deleted | tinyint(1) | YES | | NULL | | | id | int(11) | NO | PRI | NULL | auto_increment | | host | varchar(255) | YES | | NULL | | | binary | varchar(255) | YES | | NULL | | | topic | varchar(255) | YES | | NULL | | | report_count | int(11) | NO | | NULL | | | disabled | tinyint(1) | YES | | NULL | | | availability_zone | varchar(255) | YES | | NULL | | | disabled_reason | varchar(255) | YES | | NULL | | | modified_at | datetime | YES | | NULL | | | rpc_current_version | varchar(36) | YES | | NULL | | | object_current_version | varchar(36) | YES | | NULL | | | replication_status | varchar(36) | YES | | NULL | | | frozen | tinyint(1) | YES | | NULL | | | active_backend_id | varchar(255) | YES | | NULL | | | cluster_name | varchar(255) | YES | | NULL | | +------------------------+--------------+------+-----+---------+----------------+ 19 rows in set (0.01 sec)
样例
mysql> select * from services limit 2G;
*************************** 1. row ***************************
created_at: 2018-08-16 07:29:20
updated_at: 2019-06-14 09:22:23
deleted_at: NULL
deleted: 0
id: 1
host: 10.24.1.9
binary: cinder-scheduler
topic: cinder-scheduler
report_count: 838433
disabled: 0
availability_zone: nova
disabled_reason: NULL
modified_at: NULL
rpc_current_version: 3.5
object_current_version: 1.21
replication_status: not-capable
frozen: 0
active_backend_id: NULL
cluster_name: NULL
*************************** 2. row ***************************