如何进行nova.api.openstack.APIRouterV21模块的解析

如何进行nova.api.openstack.APIRouterV21模块的解析，针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。

nova.api.openstack.APIRouterV21模块的解析:

from nova import wsgi as base_wsgi class APIRouterV21(base_wsgi.Router):""" 将OpenStack v2.1 API上的请求路由到适当的控制器和方法。 """    @classmethod    def factory(cls, global_config, **local_config):"""paste factory 方法, 在/etc/nova/api-paste.ini里的[app:osapi_compute_app_v21]调用"""        return cls()@staticmethod    def api_extension_namespace():        """定义插件命名空间 """ return 'nova.api.v21.extensions'    def __init__(self):def _check_load_extension(ext):return self._register_extension(ext)        #通过stevedore 动态加载插件self.api_extension_manager = stevedore.enabled.EnabledExtensionManager(namespace=self.api_extension_namespace(),check_func=_check_load_extension,invoke_on_load=True,invoke_kwds={"extension_info": self.loaded_extension_info})        mapper = ProjectMapper()#Routes映射器，此类是nova对routes.Mapper的继承重载self.resources = {}#  核心API支持被重写为扩展，  但在概念上仍然具有核心性        if list(self.api_extension_manager):# 如果没有检测到插件，Stevedore将引发异常。             self._register_resources_check_inherits(mapper)self.api_extension_manager.map(self._register_controllers)        LOG.info(_LI("Loaded extensions: %s"),                 sorted(self.loaded_extension_info.get_extensions().keys()))super(APIRouterV21, self).__init__(mapper)def _register_resources_list(self, ext_list, mapper):for ext in ext_list:self._register_resources(ext, mapper)def _register_resources_check_inherits(self, mapper):        ext_has_inherits = []        ext_no_inherits = []for ext in self.api_extension_manager:for resource in ext.obj.get_resources():if resource.inherits:                    ext_has_inherits.append(ext)break            else:                ext_no_inherits.append(ext)self._register_resources_list(ext_no_inherits, mapper)self._register_resources_list(ext_has_inherits, mapper)@property    def loaded_extension_info(self):raise NotImplementedError()def _register_extension(self, ext):raise NotImplementedError()def _register_resources(self, ext, mapper):""" 注册由extensions定义的资源          Extensions通过get_resources函数定义要添加的资源 """        handler = ext.obj        LOG.debug("Running _register_resources on %s", ext.obj)for resource in handler.get_resources():            LOG.debug('Extended resource: %s', resource.collection)            inherits = None            if resource.inherits:                inherits = self.resources.get(resource.inherits)if not resource.controller:                    resource.controller = inherits.controller            wsgi_resource = wsgi.ResourceV21(resource.controller,                                             inherits=inherits)self.resources[resource.collection] = wsgi_resource            kargs = dict(controller=wsgi_resource,collection=resource.collection_actions,member=resource.member_actions)if resource.parent:                kargs['parent_resource'] = resource.parent# 非核心api插件使用collection名称作为member名称， # 但是core-API插件对member/collection名称使用单复数约定            if resource.member_name:                member_name = resource.member_nameelse:                member_name = resource.collection            mapper.resource(member_name, resource.collection,                            **kargs)if resource.custom_routes_fn:                resource.custom_routes_fn(mapper, wsgi_resource)def _register_controllers(self, ext):""" 注册由extensions定义的控制器         通过get_controller_extensions函数Extensions定义要添加的资源"""        handler = ext.obj        LOG.debug("Running _register_controllers on %s", ext.obj)for extension in handler.get_controller_extensions():            ext_name = extension.extension.name            collection = extension.collection            controller = extension.controllerif collection not in self.resources:                LOG.warning(_LW('Extension %(ext_name)s: Cannot extend '                                'resource %(collection)s: No such resource'),                            {'ext_name': ext_name, 'collection': collection})continue            LOG.debug('Extension %(ext_name)s extending resource: '                      '%(collection)s',                      {'ext_name': ext_name, 'collection': collection})            resource = self.resources[collection]            resource.register_actions(controller)            resource.register_extensions(controller)

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