openstack学习之neutron ml2初始化代码分析

这里没有 去详细考虑neutron server怎么初始化的，而是直接从加载插件的地方开始分析。首先我们看下下面这个文件。

Neutron/api/v2/router.py

class APIRouter(base_wsgi.Router):

    @classmethod
    def factory(cls, global_config, **local_config):
        return cls(**local_config)

    def __init__(self, **local_config):
        #用来构造了URL和对应controller映射，根据不同的URL路由给不同的controller处理。
        mapper = routes_mapper.Mapper()
        #获取NeutornManage的core_plugin，这个定义在/etc/neutron/neutron.conf,比如我的是
        #core_plugin =  neutron.plugins.ml2.plugin.Ml2Plugin
        plugin = manager.NeutronManager.get_plugin()
        # 扫描特定路径下的extensions
        ext_mgr = extensions.PluginAwareExtensionManager.get_instance()

上面给出了根据配置文件要加载哪些插件，下面正式加载插件。
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.
    The caller should make sure that NeutronManager is a singleton.
    """
    _instance = None

    def __init__(self, options=None, config_file=None):
        # If no options have been provided, create an empty dict
        if not options:
            options = {}
        # 验证是否配置了cor_plugin
        msg = validate_pre_plugin_load()
        if msg:
            LOG.critical(msg)
            raise Exception(msg)

        # NOTE(jkoelker) Testing for the subclass with the __subclasshook__
        #                breaks tach monitoring. It has been removed
        #                intentionally to allow v2 plugins to be monitored
        #                for performance metrics.
        plugin_provider = cfg.CONF.core_plugin
        #ml2 namespace: neutron.core_plugins class: neutron.plugins.ml2.plugin.Ml2Plugin（benzhang）
        LOG.info(_LI("Loading core plugin: %s"), plugin_provider)
        # 加载核心插件
        self.plugin = self._get_plugin_instance(CORE_PLUGINS_NAMESPACE,
                                                plugin_provider)

正式加载插件并初始化。

neutron/manager.py

def _get_plugin_instance(self, namespace, plugin_provider):
    plugin_class = self.load_class_for_provider(namespace, plugin_provider)
    return plugin_class() #初始化ml2plugin

核心插件ML2的初始化

neutron/plugins/ml2/plugin.py/ML2Plugin

def __init__(self):
    # First load drivers, then initialize DB, then initialize drivers
    self.type_manager = managers.TypeManager()
    self.extension_manager = managers.ExtensionManager()
    self.mechanism_manager = managers.MechanismManager()
    super(Ml2Plugin, self).__init__()
    # ML2Plugin中的初始化
    self.type_manager.initialize()
    self.extension_manager.initialize()
    self.mechanism_manager.initialize()
    self._setup_dhcp()
    self._start_rpc_notifiers()
    self.add_agent_status_check(self.agent_health_check)
    self._verify_service_plugins_requirements()
    LOG.info(_LI("Modular L2 Plugin initialization complete"))

初始化Type driver
neutron/plugins/ml2/manager.py
class TypeManager(stevedore.named.NamedExtensionManager):
“”“Manage network segment types using drivers.”“”

def __init__(self):
    # Mapping from type name to DriverManager
    self.drivers = {}

    LOG.info(_LI("Configured type driver names: %s"),
             cfg.CONF.ml2.type_drivers)
    super(TypeManager, self).__init__('neutron.ml2.type_drivers',
                                      cfg.CONF.ml2.type_drivers,
                                      invoke_on_load=True)
    # 此处是根据/etc/neutron/plugins/ml2/ml2_conf.ini中配置的type_drivers，
    # 到/usr/lib/python2.7/site-packages/neutron-10.0.1-py2.7.egg-info/ entry_points.txt
    # 文件中的neutron.ml2.type_drivers字段读取driver初始化入口，也就是类代码的位置
    LOG.info(_LI("Loaded type driver names: %s"), self.names())
    # 注册 type driver
    self._register_types()
    # 校验并注册tenant_network_types
    self._check_tenant_network_types(cfg.CONF.ml2.tenant_network_types)
    # 校验external_network_type
    self._check_external_network_type(cfg.CONF.ml2.external_network_type)

neutron/plugins/ml2/manager.py
def initialize(self):
for network_type, driver in six.iteritems(self.drivers):
LOG.info(_LI(“Initializing driver for type ‘%s’”), network_type)
#对配置每一种type进行初始化，例如：flat，vlan
driver.obj.initialize()

初始化 Mechanism
neutron/plugins/ml2/manager.py
class MechanismManager(stevedore.named.NamedExtensionManager):
“”“Manage networking mechanisms using drivers.”“”

def __init__(self):
    # Registered mechanism drivers, keyed by name.
    self.mech_drivers = {}
    # Ordered list of mechanism drivers, defining
    # the order in which the drivers are called.
    self.ordered_mech_drivers = []

    LOG.info(_LI("Configured mechanism driver names: %s"),
             cfg.CONF.ml2.mechanism_drivers)
    super(MechanismManager, self).__init__('neutron.ml2.mechanism_drivers',
                                           cfg.CONF.ml2.mechanism_drivers,
                                           invoke_on_load=True,
                                           name_order=True)
    # 此处是根据/etc/neutron/plugins/ml2/ml2_conf.ini中配置的mechanism_drivers，
    # 到/usr/lib/python2.7/site-packages/neutron-10.0.1-py2.7.egg-info/ entry_points.txt
    # 文件中的neutron.ml2.mechanism_drivers字段读取driver初始化入口，也就是类代码的位置
    LOG.info(_LI("Loaded mechanism driver names: %s"), self.names())
    self._register_mechanisms()

初始化 Extension
neutron/plugins/ml2/manager.py
class ExtensionManager(stevedore.named.NamedExtensionManager):
“”“Manage extension drivers using drivers.”“”

def __init__(self):
    # Ordered list of extension drivers, defining
    # the order in which the drivers are called.
    self.ordered_ext_drivers = []

    LOG.info(_LI("Configured extension driver names: %s"),
             cfg.CONF.ml2.extension_drivers)
    super(ExtensionManager, self).__init__('neutron.ml2.extension_drivers',
                                           cfg.CONF.ml2.extension_drivers,
                                           invoke_on_load=True,
                                           name_order=True)
# 此处是根据/etc/neutron/plugins/ml2/ml2_conf.ini中配置的extension_drivers，
    # 到/usr/lib/python2.7/site-packages/neutron-10.0.1-py2.7.egg-info/ entry_points.txt
    # 文件中的neutron.ml2.extension_drivers字段读取driver初始化入口，也就是类代码的位置
    LOG.info(_LI("Loaded extension driver names: %s"), self.names())
    self._register_drivers()

待续~