ipa和ironic-conductor交互

IPA使用lookup和hearteat机制与Ironic Conductor进行交互，启动时agent给Conductor的vendor_passthru lookup endpoint（地址为/v1/drivers/{driver}/vendor_passthru/lookup）发送一个硬件的profile，
然后Ironic就可以得出该节点的uuid，在成功发现该节点之后，agent隔N秒发送心跳包给Conductor（hearteat地址为/v1/nodes/{node_ident}/vendor_passthru/heartbeat ），conductor执行一系列动作，包括查询已经运行的命令的状态，启动带内清洁任务或将镜像部署到节点。

#主函数入口，定义了IronicPythonAgent类的对象， 初始化它，并调用该对象的run()函数.
#机器上电后，ramdisk在内存中执行，然后启动IPA，入口为cmd.agent.run()，
#然后调用ironic-python-agent.agent.run()，其代码如下：

def run(self):
        """Run the Ironic Python Agent."""
        # Get the UUID so we can heartbeat to Ironic. Raises LookupNodeError
        # if there is an issue (uncaught, restart agent)
        self.started_at = _time()
#运行ipa，获取node的uuid，发送心跳包
        # Cached hw managers at runtime, not load time. See bug 1490008.
        hardware.load_managers()
#调用hardwarre.load_managers加载硬件到缓存，以优先级顺序获取硬件管理器的列表。
        # Operator-settable delay before hardware actually comes up.
        # Helps with slow RAID drivers - see bug 1582797.
        if self.hardware_initialization_delay > 0:
            LOG.info('Waiting %d seconds before proceeding',
                     self.hardware_initialization_delay)
            time.sleep(self.hardware_initialization_delay)
#该函数中会判断是否为standalone模式启动，如果不是，则会向ironic-api查询当前节点的信息，比如uuid等：
        if not self.standalone:
            # Inspection should be started before call to lookup, otherwise
            # lookup will fail due to unknown MAC.
            uuid = None
            if cfg.CONF.inspection_callback_url:
                uuid = inspector.inspect()
#利用Ironic API给Condutor发送lookup()请求，用户获取UUID，相当于自发现
            if self.api_url:
                self._wait_for_interface()
#此处会调取ironic_python_agent.agent._wait_for_interface函数，
#通过ironic_python_agent.hardware.dispatch_to_managers获取网卡信息
                content = self.api_client.lookup_node(
#调用到ironic_python_agent.ironic_api_client.lookup_node的_do_lookup()，
#然后发送一个GET /{api_version}/drivers/{driver}/vendor_passthru/lookup请求。
#Condutor API在接受到lookup请求后调用指定驱动的lookup函数处理，返回节点UUID。

                    hardware_info=hardware.dispatch_to_managers(
                        'list_hardware_info'),
#调取ironic_python_agent.hardware.dispatch_to_managers获取硬件信息列表
                    timeout=self.lookup_timeout,
                    starting_interval=self.lookup_interval,
                    node_uuid=uuid)

                LOG.debug('Received lookup results: %s', content)
                self.node = content['node']
                LOG.info('Lookup succeeded, node UUID is %s',
                         self.node['uuid'])
                hardware.cache_node(self.node)
                self.heartbeat_timeout = content['config']['heartbeat_timeout']

                # Update config with values from Ironic
                config = content.get('config', {})
                if config.get('metrics'):
                    for opt, val in config.items():
                        setattr(cfg.CONF.metrics, opt, val)
                if config.get('metrics_statsd'):
                    for opt, val in config.items():
                        setattr(cfg.CONF.metrics_statsd, opt, val)
            elif cfg.CONF.inspection_callback_url:
                LOG.info('No ipa-api-url configured, Heartbeat and lookup '
                         'skipped for inspector.')
            else:
                LOG.error('Neither ipa-api-url nor inspection_callback_url'
                          'found, please check your pxe append parameters.')

        self.serve_ipa_api()#调取ironic_python_agent.agent.serve_ipa_api，创建一个wsgi的server服务对象，发送心跳包

        if not self.standalone and self.api_url:
            self.heartbeater.stop()
#部署完成后停止心跳包