api-paste.ini

定义了WSGI应用和路由信息。利用Paste来实例化Neutron的APIRouter类，将资源（端口、网络、子网）映射到URL上，以及各个资源的控制器。
在neutron-server启动的时候，一般会指定参数—config-file neutron.conf —config-file xxx.ini。看neutron/server/init.py的代码: main()主程序中会调用config.parse(sys.argv[1:])来读取这些配置文件中的信息。而api-paste.ini信息中定义了neutron、neutronapi_v2_0、若干filter和两个app。

  1. [composite:neutron]
  2. use = egg:Paste#urlmap
  3. /: neutronversions
  4. /v2.0: neutronapi_v2_0
  6. [composite:neutronapi_v2_0]
  7. use = call:neutron.auth:pipeline_factory
  8. noauth = request_id catch_errors extensions neutronapiapp_v2_0
  9. keystone = request_id catch_errors authtoken keystonecontext extensions neutronapiapp_v2_0
  11. [filter:request_id]
  12. paste.filter_factory = oslo.middleware:RequestId.factory
  14. [filter:catch_errors]
  15. paste.filter_factory = oslo.middleware:CatchErrors.factory
  17. [filter:keystonecontext]
  18. paste.filter_factory = neutron.auth:NeutronKeystoneContext.factory
  20. [filter:authtoken]
  21. paste.filter_factory = keystonemiddleware.auth_token:filter_factory
  23. [filter:extensions]
  24. paste.filter_factory = neutron.api.extensions:plugin_aware_extension_middleware_factory
  26. [app:neutronversions]
  27. paste.app_factory = neutron.api.versions:Versions.factory
  29. [app:neutronapiapp_v2_0]
  30. paste.app_factory = neutron.api.v2.router:APIRouter.factory

neutron-server在读取完配置信息后，会执行neutron/common/config.py:load_paste_app(“neutron”)，即将neutron应用load进来。从api-paste.ini中可以看到，neutron实际上是一个composite，分别将URL“/”和“/v2.0”映射到neutronversions应用和neutronapi_v2_0（也是一个composite）。

前者实际上调用了 neutron.api.versions 模块中的 Versions.factory 来处理传入的请求。

后者则要复杂一些，首先调用 neutron.auth 模块中的pipeline_factory 处理。如果是 noauth，则传入参数为 request_id，catch_errors，extensions 这些 filter和 neutronapiapp_v2_0 应用；如果是 keystone，则多传入一个 authtoken filter，最后一个参数仍然是 neutronapiapp_v2_0 应用。来看 neutron.auth 模块中的 pipeline_factory 处理代码。

  1. def pipeline_factory(loader, global_conf, **local_conf):
  2.     """Create a paste pipeline based on the 'auth_strategy' config option."""
  3.     pipeline = local_conf[cfg.CONF.auth_strategy]
  4.     pipeline = pipeline.split()
  5.     filters = [loader.get_filter(n) for n in pipeline[:-1]]
  6.     app = loader.get_app(pipeline[-1])
  7.     filters.reverse()
  8.     for filter in filters:
  9.         app = filter(app)
  10.     return app

最终的代码入口是neutron.api.v2.router:APIRouter.factory。该方法主要代码为

  1. class APIRouter(wsgi.Router):
  3.     @classmethod
  4.     def factory(cls, global_config, **local_config):
  5.         return cls(**local_config)
  7.     def __init__(self, **local_config):
  8.         mapper = routes_mapper.Mapper()
  9.         plugin = manager.NeutronManager.get_plugin()
  10.         ext_mgr = extensions.PluginAwareExtensionManager.get_instance()
  11.         ext_mgr.extend_resources("2.0", attributes.RESOURCE_ATTRIBUTE_MAP)
  13.         col_kwargs = dict(collection_actions=COLLECTION_ACTIONS,
  14.                           member_actions=MEMBER_ACTIONS)
  16.         def _map_resource(collection, resource, params, parent=None):
  17.             allow_bulk = cfg.CONF.allow_bulk
  18.             allow_pagination = cfg.CONF.allow_pagination
  19.             allow_sorting = cfg.CONF.allow_sorting
  20.             controller = base.create_resource(
  21.                 collection, resource, plugin, params, allow_bulk=allow_bulk,
  22.                 parent=parent, allow_pagination=allow_pagination,
  23.                 allow_sorting=allow_sorting)
  24.             path_prefix = None
  25.             if parent:
  26.                 path_prefix = "/%s/{%s_id}/%s" % (parent['collection_name'],
  27.                                                   parent['member_name'],
  28.                                                   collection)
  29.             mapper_kwargs = dict(controller=controller,
  30.                                  requirements=REQUIREMENTS,
  31.                                  path_prefix=path_prefix,
  32.                                  **col_kwargs)
  33.             return mapper.collection(collection, resource,
  34.                                      **mapper_kwargs)
  36.         mapper.connect('index', '/', controller=Index(RESOURCES))
  37.         for resource in RESOURCES:
  38.             _map_resource(RESOURCES[resource], resource,
  39.                           attributes.RESOURCE_ATTRIBUTE_MAP.get(
  40.                               RESOURCES[resource], dict()))
  42.         for resource in SUB_RESOURCES:
  43.             _map_resource(SUB_RESOURCES[resource]['collection_name'], resource,
  44.                           attributes.RESOURCE_ATTRIBUTE_MAP.get(
  45.                               SUB_RESOURCES[resource]['collection_name'],
  46.                               dict()),
  47.                           SUB_RESOURCES[resource]['parent'])

neutron server启动后，根据配置文件动态加载对应的core plugin 和 service plugin。neturon server 中会对收到的 rest api 请求进行解析，并最终转换成对该 plugin(core or service) 中相应方法的调用。