nova下的service.py的源碼，今天閱讀之后 直接就把我理解的以注釋的形式添加到了源碼中，有些地方不好或者是錯了，希望大家幫我指出！

?

import?inspect ?

import?os ?

?

import?eventlet ?

import?greenlet ?

?

from?nova?import?context ?

from?nova?import?db ?

from?nova?import?exception ?

from?nova?import?flags ?

from?nova?import?log?as?logging ?

from?nova?import?rpc ?

from?nova?import?utils ?

from?nova?import?version ?

from?nova?import?wsgi ?

?

?

LOG?=?logging.getLogger('nova.service') ?

?

FLAGS?=?flags.FLAGS#flags.py中有一句?FLAGS?=?FlagValues()，那么直接查看FlagValues()這個類，會發現這個類是繼承于gflags.FlagValues. ?

?

flags.DEFINE_integer('report_interval',?10, ?

?????????????????????'seconds?between?nodes?reporting?state?to?datastore', ?

?????????????????????lower_bound=1)#參數名稱，默認值和簡短說明 ?

flags.DEFINE_integer('periodic_interval',?60, ?

?????????????????????'seconds?between?running?periodic?tasks', ?

?????????????????????lower_bound=1) ?

flags.DEFINE_string('ec2_listen',?"0.0.0.0", ?

????????????????????'IP?address?for?EC2?API?to?listen') ?

flags.DEFINE_integer('ec2_listen_port',?8773,?'port?for?ec2?api?to?listen') ?

flags.DEFINE_string('osapi_listen',?"0.0.0.0", ?

????????????????????'IP?address?for?OpenStack?API?to?listen') ?

flags.DEFINE_integer('osapi_listen_port',?8774,?'port?for?os?api?to?listen') ?

flags.DEFINE_string('api_paste_config',?"api-paste.ini", ?

????????????????????'File?name?for?the?paste.deploy?config?for?nova-api') ?

?

#Launcher?類?包含run_server?,launch_server,stop,wait?4個函數，其實功能非常簡單，首先初始化Launcher將self_services弄成一個空列表 ?

#run_server就是開始和等待一個server的完成，launcher_server就是將該server加入到該類初始化的列表中， ?

#stop?就是for循環遍歷self_services列表中的服務然后一個一個的kill掉 ?

#wait?函數就是?Waits?until?all?services?have?been?stopped ?

class?Launcher(object): ?

????"""Launch?one?or?more?services?and?wait?for?them?to?complete."""?

?

????def?__init__(self): ?

????????"""Initialize?the?service?launcher. ?

?

????????:returns:?None ?

?

????????"""?

????????self._services?=?[] ?

?

????@staticmethod?

????def?run_server(server): ?

????????"""Start?and?wait?for?a?server?to?finish. ?

?

????????:param?service:?Server?to?run?and?wait?for. ?

????????:returns:?None ?

?

????????"""?

????????server.start() ?

????????server.wait() ?

?

????def?launch_server(self,?server):#在360行被調用 ?

????????"""Load?and?start?the?given?server. ?

?

????????:param?server:?The?server?you?would?like?to?start. ?

????????:returns:?None ?

?

????????"""?

????????gt?=?eventlet.spawn(self.run_server,?server) ?

????????self._services.append(gt) ?

?

????def?stop(self): ?

????????"""Stop?all?services?which?are?currently?running. ?

?

????????:returns:?None ?

?

????????"""?

????????for?service?in?self._services: ?

????????????service.kill() ?

?

????def?wait(self): ?

????????"""Waits?until?all?services?have?been?stopped,?and?then?returns. ?

?

????????:returns:?None ?

?

????????"""?

????????for?service?in?self._services: ?

????????????try: ?

????????????????service.wait() ?

????????????except?greenlet.GreenletExit: ?

????????????????pass?

?

?

class?Service(object): ?

????"""Service?object?for?binaries?running?on?hosts. ?

?

????A?service?takes?a?manager?and?enables?rpc?by?listening?to?queues?based ?

????on?topic.?It?also?periodically?runs?tasks?on?the?manager?and?reports ?

????it?state?to?the?database?services?table."""?

?

????def?__init__(self,?host,?binary,?topic,?manager,?report_interval=None, ?

?????????????????periodic_interval=None,?*args,?**kwargs): ?

????????self.host?=?host ?

????????self.binary?=?binary ?

????????self.topic?=?topic ?

????????#動態的生成manager類，并動態生成實例 ?

????????self.manager_class_name?=?manager#在create函數中指定 ?

????????manager_class?=?utils.import_class(self.manager_class_name)#動態的import該類 ?

????????self.manager?=?manager_class(host=self.host,?*args,?**kwargs)#動態的生成實例 ?

????????#??設置參數：應該是服務間隔時間之類的。 ?

????????self.report_interval?=?report_interval ?

????????self.periodic_interval?=?periodic_interval ?

????????#設置多出來的一些參數。 ?

????????super(Service,?self).__init__(*args,?**kwargs) ?

????????self.saved_args,?self.saved_kwargs?=?args,?kwargs ?

????????#設置一個列表?不知道是不是后面有需要用的地方?果然在185行?發現了 ?

????????self.timers?=?[] ?

?

????def?start(self): ?

????????#設置版本 ?

????????vcs_string?=?version.version_string_with_vcs() ?

????????logging.audit(_('Starting?%(topic)s?node?(version?%(vcs_string)s)'), ?

??????????????????????{'topic':?self.topic,?'vcs_string':?vcs_string}) ?

????????#初始化host ?

????????self.manager.init_host() ?

???????? ?

????????self.model_disconnected?=?False?

????????ctxt?=?context.get_admin_context() ?

????????try: ?

????????????service_ref?=?db.service_get_by_args(ctxt, ?

?????????????????????????????????????????????????self.host, ?

?????????????????????????????????????????????????self.binary) ?

????????????self.service_id?=?service_ref['id'] ?

????????except?exception.NotFound: ?

????????????self._create_service_ref(ctxt)#該函數位于187行 ?

?

????????if?'nova-compute'?==?self.binary: ?

????????????self.manager.update_available_resource(ctxt) ?

?

????????self.conn?=?rpc.create_connection(new=True) ?

????????logging.debug("Creating?Consumer?connection?for?Service?%s"?% ?

??????????????????????self.topic) ?

?

????????#?Share?this?same?connection?for?these?Consumers ?

????????self.conn.create_consumer(self.topic,?self,?fanout=False) ?

?

????????node_topic?=?'%s.%s'?%?(self.topic,?self.host)#節點的topic?包括了topic?和?host ?

????????self.conn.create_consumer(node_topic,?self,?fanout=False) ?

?

????????self.conn.create_consumer(self.topic,?self,?fanout=True) ?

?

????????#?Consume?from?all?consumers?in?a?thread ?

????????self.conn.consume_in_thread() ?

?

????????if?self.report_interval: ?

????????????pulse?=?utils.LoopingCall(self.report_state)#在265中可以找到report_state?他的作用是在存儲中更新服務的狀態 ?

????????????pulse.start(interval=self.report_interval,?now=False) ?

????????????self.timers.append(pulse) ?

?

????????if?self.periodic_interval: ?

????????????periodic?=?utils.LoopingCall(self.periodic_tasks)#在260行發現?Periodic_tasks任務在一個周期性間隔跑 ?

????????????periodic.start(interval=self.periodic_interval,?now=False) ?

????????????self.timers.append(periodic) ?

?

????def?_create_service_ref(self,?context): ?

????????zone?=?FLAGS.node_availability_zone ?

????????service_ref?=?db.service_create(context, ?

????????????????????????????????????????{'host':?self.host, ?

?????????????????????????????????????????'binary':?self.binary, ?

?????????????????????????????????????????'topic':?self.topic, ?

?????????????????????????????????????????'report_count':?0, ?

?????????????????????????????????????????'availability_zone':?zone}) ?

????????self.service_id?=?service_ref['id']#猜測應該是獲取當前服務的id ?

?

????def?__getattr__(self,?key): ?

????????manager?=?self.__dict__.get('manager',?None) ?

????????return?getattr(manager,?key) ?

?

????@classmethod?

????def?create(cls,?host=None,?binary=None,?topic=None,?manager=None, ?

???????????????report_interval=None,?periodic_interval=None): ?

????????"""Instantiates?class?and?passes?back?application?object. ?

?

????????:param?host:?defaults?to?FLAGS.host ?

????????:param?binary:?defaults?to?basename?of?executable ?

????????:param?topic:?defaults?to?bin_name?-?'nova-'?part ?

????????:param?manager:?defaults?to?FLAGS.<topic>_manager ?

????????:param?report_interval:?defaults?to?FLAGS.report_interval ?

????????:param?periodic_interval:?defaults?to?FLAGS.periodic_interval ?

?

????????"""?

????????if?not?host: ?

????????????host?=?FLAGS.host ?

????????if?not?binary: ?

????????????binary?=?os.path.basename(inspect.stack()[-1][1]) ?

????????if?not?topic: ?

????????????topic?=?binary.rpartition('nova-')[2] ?

????????if?not?manager: ?

????????????manager?=?FLAGS.get('%s_manager'?%?topic,?None) ?

????????if?not?report_interval: ?

????????????report_interval?=?FLAGS.report_interval ?

????????if?not?periodic_interval: ?

????????????periodic_interval?=?FLAGS.periodic_interval ?

????????service_obj?=?cls(host,?binary,?topic,?manager, ?

??????????????????????????report_interval,?periodic_interval)#此處?調用的是該類的init的默認函數????? ?

?

????????return?service_obj ?

?

????def?kill(self): ?

????????"""Destroy?the?service?object?in?the?datastore."""?

????????self.stop() ?

????????try: ?

????????????db.service_destroy(context.get_admin_context(),?self.service_id) ?

????????except?exception.NotFound: ?

????????????logging.warn(_('Service?killed?that?has?no?database?entry')) ?

?

????def?stop(self): ?

????????#?Try?to?shut?the?connection?down,?but?if?we?get?any?sort?of ?

????????#?errors,?go?ahead?and?ignore?them..?as?we're?shutting?down?anyway ?

????????try: ?

????????????self.conn.close() ?

????????except?Exception: ?

????????????pass?

????????for?x?in?self.timers:???#遍歷曾經添加到self.timers中的每一個“間隔”（不是很清楚）?然后將其stop ?

????????????try: ?

????????????????x.stop() ?

????????????except?Exception: ?

????????????????pass?

????????self.timers?=?[]?#重新將self.timers置空 ?

?

????def?wait(self): ?

????????for?x?in?self.timers: ?

????????????try: ?

????????????????x.wait() ?

????????????except?Exception: ?

????????????????pass?

?

????def?periodic_tasks(self): ?

????????"""Tasks?to?be?run?at?a?periodic?interval."""?

????????#任務在一個周期性間隔跑 ?

????????self.manager.periodic_tasks(context.get_admin_context()) ?

?

????def?report_state(self): ?

????????"""Update?the?state?of?this?service?in?the?datastore."""?

????????#在數據存儲更新服務的狀態。 ?

????????ctxt?=?context.get_admin_context() ?

????????try: ?

????????????try: ?

????????????????service_ref?=?db.service_get(ctxt,?self.service_id) ?

????????????except?exception.NotFound: ?

????????????????logging.debug(_('The?service?database?object?disappeared,?'?

????????????????????????????????'Recreating?it.')) ?

????????????????self._create_service_ref(ctxt) ?

????????????????service_ref?=?db.service_get(ctxt,?self.service_id) ?

?

????????????db.service_update(ctxt, ?

?????????????????????????????self.service_id, ?

?????????????????????????????{'report_count':?service_ref['report_count']?+?1}) ?

?

????????????#?TODO(termie):?make?this?pattern?be?more?elegant. ?

????????????if?getattr(self,?'model_disconnected',?False): ?

????????????????self.model_disconnected?=?False?

????????????????logging.error(_('Recovered?model?server?connection!')) ?

?

????????#?TODO(vish):?this?should?probably?only?catch?connection?errors ?

????????except?Exception:??#?pylint:?disable=W0702 ?

????????????if?not?getattr(self,?'model_disconnected',?False): ?

????????????????self.model_disconnected?=?True?

????????????????logging.exception(_('model?server?went?away')) ?

?

?

class?WSGIService(object): ?

????"""Provides?ability?to?launch?API?from?a?'paste'?configuration."""?

????#提供能夠從一個‘paste’配置啟動api的服務 ?

?

????def?__init__(self,?name,?loader=None): ?

????????"""Initialize,?but?do?not?start?the?WSGI?server. ?

?

????????:param?name:?The?name?of?the?WSGI?server?given?to?the?loader. ?

????????:param?loader:?Loads?the?WSGI?application?using?the?given?name. ?

????????:returns:?None ?

?

????????"""?

????????#初始化?但是并沒有開是wsgi的服務。 ?

????????self.name?=?name ?

????????self.loader?=?loader?or?wsgi.Loader() ?

????????self.app?=?self.loader.load_app(name)#將wsgi服務的名字給到self.loader,然后用那名字將其?裝載到wsgi?application ?

????????self.host?=?getattr(FLAGS,?'%s_listen'?%?name,?"0.0.0.0")?#返回主機host?getattr?Found?at:?__builtin__ ?

????????#getattr(object,?name[,?default])?->?value得知返回的是value ?

?

?

????????self.port?=?getattr(FLAGS,?'%s_listen_port'?%?name,?0)#端口?port ?

????????self.server?=?wsgi.Server(name, ?

??????????????????????????????????self.app, ?

??????????????????????????????????host=self.host, ?

??????????????????????????????????port=self.port) ?

?

????def?start(self): ?

????????"""Start?serving?this?service?using?loaded?configuration. ?

?

????????Also,?retrieve?updated?port?number?in?case?'0'?was?passed?in,?which ?

????????indicates?a?random?port?should?be?used. ?

?

????????:returns:?None ?

?

????????"""?

????????self.server.start() ?

????????self.port?=?self.server.port ?

?

????def?stop(self): ?

????????"""Stop?serving?this?API. ?

?

????????:returns:?None ?

?

????????"""?

????????self.server.stop() ?

?

????def?wait(self): ?

????????"""Wait?for?the?service?to?stop?serving?this?API. ?

?

????????:returns:?None ?

?

????????"""?

????????self.server.wait() ?

?

?

#?NOTE(vish):?the?global?launcher?is?to?maintain?the?existing ?

#?????????????functionality?of?calling?service.serve?+ ?

#?????????????service.wait ?

_launcher?=?None?

?

?

def?serve(*servers): ?

????global?_launcher ?

????if?not?_launcher: ?

????????_launcher?=?Launcher()?#s實例化Launcher ?

????for?server?in?servers: ?

????????_launcher.launch_server(server) ?

?

?

def?wait(): ?

????#?After?we've?loaded?up?all?our?dynamic?bits,?check ?

????#?whether?we?should?print?help ?

???? ?

?

????#flags.py中?有一句 ?

????#FLAGS?=?FlagValues()，那么直接查看FlagValues()這個類，這個類是繼承于gflags.FlagValues. ?

?

?

????flags.DEFINE_flag(flags.HelpFlag()) ?

????flags.DEFINE_flag(flags.HelpshortFlag()) ?

????flags.DEFINE_flag(flags.HelpXMLFlag()) ?

????FLAGS.ParseNewFlags() ?

????logging.debug(_('Full?set?of?FLAGS:')) ?

????for?flag?in?FLAGS: ?

????????flag_get?=?FLAGS.get(flag,?None) ?

????????logging.debug('%(flag)s?:?%(flag_get)s'?%?locals()) ?

????try: ?

????????_launcher.wait() ?

????except?KeyboardInterrupt: ?

????????_launcher.stop() ?

?

轉載于:https://blog.51cto.com/brucemars/965124

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