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~