Neutron 代码阅读笔记

Neutron代码架构主要分为三个部分：
1、server ：负责RESTfulAPI的路由分发，把请求路由到相应的plugin处理
2、plugin：负责处理具体的资源业务组装，校验，入库，然后通过rpc发给agent具体处理
3、agent：具体的执行任务

neutron server

• 服务入口：\neutron\cmd\eventlet\server__init__.py:main()
• API路由分发：/neutron/api/v2/router.py

class APIRouter(base_wsgi.Router):

    @classmethod
    def factory(cls, global_config, **local_config):
        if cfg.CONF.web_ramework == 'pecan':
            return pecan_app.v2_factory(global_config, **local_config)
        return cls(**local_config)
    def __init__(self, **local_config):
        mapper = routes_mapper.Mapper()
        manager.init()

主要是： manager.init()

• 生成单例模式的NeutronManager：/neutron/manager.py

def init():
    """Call to load the plugins (core+services) machinery."""
    if not directory.is_loaded():
        NeutronManager.get_instance()

• 加载core plugin和services plugins： /neutron/manager.py

class NeutronManager(object):
    """Neutron's Manager class.
    Neutron's Manager class is responsible for parsing a config file and
    instantiating the correct plugin that concretely implements
    neutron_plugin_base class.
    """
    _instance = None
    __trace_args__ = {"name": "rpc"}
    def __init__(self, options=None, config_file=None):
        # If no options have been provided, create an empty dict
        if not options:
            options = {}
        msg = validate_pre_plugin_load()

        if msg:
            LOG.critical(msg)
            raise Exception(msg)

        plugin_provider = cfg.CONF.core_plugin
        LOG.info("Loading core plugin: %s", plugin_provider)
        plugin = self._get_plugin_instance(CORE_PLUGINS_NAMESPACE,
                                           plugin_provider)
        directory.add_plugin(lib_const.CORE, plugin)
        msg = validate_post_plugin_load()
        if msg:
            LOG.critical(msg)
            raise Exception(msg)
	   # 加载 core plugin --------------------------------------------------------------------
        self._load_services_from_core_plugin(plugin)
        # 加载 services plugin ---------------------------------------------------------------
        self._load_service_plugins()
        # Used by pecan WSGI
        self.resource_plugin_mappings = {}
        self.resource_controller_mappings = {}
        self.path_prefix_resource_mappings = defaultdict(list)

• 分别加载配置文件中的plugin：
  /etc/kolla/neutron-server/neutron.conf

[DEFAULT]
debug = True
api_paste_config = /usr/share/neutron/api-paste.ini
...
core_plugin = ml2
service_plugins = firewall,qos,router,cnpconn

• service plugins的加载代码：

    def _load_service_plugins(self):
        """Loads service plugins.
        Starts from the core plugin and checks if it supports
        advanced services then loads classes provided in configuration.
        """
        # 配置文件neutron.conf中定义的service_plugins
        plugin_providers = cfg.CONF.service_plugins
        # 代码中写死的 默认的service_plugins
        plugin_providers.extend(self._get_default_service_plugins())
        LOG.debug("Loading service plugins: %s", plugin_providers)
        for provider in plugin_providers:
            if provider == '':
                continue
           ...

• 默认的plugin位置：/neutron/plugins/common/constants.py
  constants.py中的默认service plugin和neutron.conf中定义的service plugin一个位置有就可以了。

DEFAULT_SERVICE_PLUGINS = {
    'auto_allocate': 'auto-allocated-topology',
    'tag': 'tag',
    'timestamp': 'timestamp',
    'network_ip_availability': 'network-ip-availability',
    'flavors': 'flavors',
    'revisions': 'revisions',
}

总结：要加载自定义组件有两种方式：
1、将写好的plugins以配置文件方式加入neutron.conf中；
2、在constants.py中DEFAULT_SERVICE_PLUGINS下加入plugin