Neutron分析（2）——neutron-server启动过程分析

neutron-server启动过程分析

1. /etc/init.d/neutron-server

DAEMON=/usr/bin/neutron-server
DAEMON_ARGS="--log-file=$LOGFILE"
DAEMON_DIR=/var/run
...
case $1 in
    start)
        test "$ENABLED" = "true" || exit 0
        log_daemon_msg "Starting neutron server" "neutron-server"
        start-stop-daemon -Sbmv --pidfile $PIDFILE --chdir $DAEMON_DIR --exec $DAEMON -- $DAEMON_ARGS
        log_end_msg $?
        ;;
        ...
esac

2. /usr/bin/neutron-server

import sys
from neutron.server import main

if __name__ == "__main__":
    sys.exit(main())

3. neutron.server.main

ef main():
    # the configuration will be read into the cfg.CONF global data structure
    config.init(sys.argv[1:])
    if not cfg.CONF.config_file:
        sys.exit(_("ERROR: Unable to find configuration file via the default"
                   " search paths (~/.neutron/, ~/, /etc/neutron/, /etc/) and"
                   " the '--config-file' option!"))
    try:
        pool = eventlet.GreenPool()

        # 以协程方式启动Restful API
        neutron_api = service.serve_wsgi(service.NeutronApiService)
        api_thread = pool.spawn(neutron_api.wait)

        # 启动RPC API
        try:
            neutron_rpc = service.serve_rpc()
        except NotImplementedError:
            LOG.info(_("RPC was already started in parent process by plugin."))
        else:
            rpc_thread = pool.spawn(neutron_rpc.wait)

            # api and rpc should die together.  When one dies, kill the other.
            rpc_thread.link(lambda gt: api_thread.kill())
            api_thread.link(lambda gt: rpc_thread.kill())

        pool.waitall()
    except KeyboardInterrupt:
        pass
    except RuntimeError as e:
        sys.exit(_("ERROR: %s") % e)

4. 先看neutron.service.serve_rpc()

neutron.service.serve_rpc()最重要的工作就是启动各个插件的RpcWorker

plugin = manager.NeutronManager.get_plugin()

try:
        rpc = RpcWorker(plugin)

        if cfg.CONF.rpc_workers < 1:
            rpc.start()
            return rpc
        else:
            launcher = common_service.ProcessLauncher(wait_interval=1.0)
            launcher.launch_service(rpc, workers=cfg.CONF.rpc_workers)
            return launcher

而RpcWorker最重要的工作是调用plugin的start_rpc_listeners来监听消息队列：

def start(self):
        # We may have just forked from parent process.  A quick disposal of the
        # existing sql connections avoids producing errors later when they are
        # discovered to be broken.
        session.get_engine().pool.dispose()
        self._servers = self._plugin.start_rpc_listeners()

5. 再来看Rest API部分

service.serve_wsgi(service.NeutronApiService)

def serve_wsgi(cls):

    try:
        service = cls.create()
        service.start()
    except Exception:
        with excutils.save_and_reraise_exception():
            LOG.exception(_('Unrecoverable error: please check log '
                            'for details.'))

    return service

service.start()即为self.wsgi_app = _run_wsgi(self.app_name)，而该函数最重要的工作是从api-paste.ini中加载app并启动

def _run_wsgi(app_name):
    app = config.load_paste_app(app_name)
    if not app:
        LOG.error(_('No known API applications configured.'))
        return
    server = wsgi.Server("Neutron")
    server.start(app, cfg.CONF.bind_port, cfg.CONF.bind_host,
                 workers=cfg.CONF.api_workers)
    # Dump all option values here after all options are parsed
    cfg.CONF.log_opt_values(LOG, std_logging.DEBUG)
    LOG.info(_("Neutron service started, listening on %(host)s:%(port)s"),
             {'host': cfg.CONF.bind_host,
              'port': cfg.CONF.bind_port})
    return server

6. api-paste.ini

[composite:neutron]
use = egg:Paste#urlmap
/: neutronversions
/v2.0: neutronapi_v2_0

[composite:neutronapi_v2_0]
use = call:neutron.auth:pipeline_factory
noauth = request_id catch_errors extensions neutronapiapp_v2_0
keystone = request_id catch_errors authtoken keystonecontext extensions neutronapiapp_v2_0

[filter:request_id]
paste.filter_factory = neutron.openstack.common.middleware.request_id:RequestIdMiddleware.factory

[filter:catch_errors]
paste.filter_factory = neutron.openstack.common.middleware.catch_errors:CatchErrorsMiddleware.factory

[filter:keystonecontext]
paste.filter_factory = neutron.auth:NeutronKeystoneContext.factory

[filter:authtoken]
paste.filter_factory = keystoneclient.middleware.auth_token:filter_factory

[filter:extensions]
paste.filter_factory = neutron.api.extensions:plugin_aware_extension_middleware_factory

[app:neutronversions]
paste.app_factory = neutron.api.versions:Versions.factory

[app:neutronapiapp_v2_0]
paste.app_factory = neutron.api.v2.router:APIRouter.factory

实例化neutron/api/v2/router.py中的APIRouter

1. class APIRouter(wsgi.Router):
2. # 一个工厂类方法
3. @classmethod
4. def factory(cls, global_config, **local_config):
5. return cls(**local_config)
6. # 真正调用的实例化方法
7. def __init__(self, **local_config):
8. ...
9. #获取NeutornManage的core_plugin，这个定义在/etc/neutron/neutron.conf,比如我的是
10. #core_plugin = neutron.plugins.openvswitch.ovs_neutron_plugin.OVSNeutronPluginV2
11. plugin = manager.NeutronManager.get_plugin()
12. #扫描特定路径下的extensions
13. ext_mgr = extensions.PluginAwareExtensionManager.get_instance()
14. ...
15. #定义的局部方法
16. def _map_resource(collection, resource, params, parent=None):
17. ...
18. controller = base.create_resource(
19. collection, resource, plugin, params, allow_bulk=allow_bulk,
20. parent=parent, allow_pagination=allow_pagination,
21. allow_sorting=allow_sorting)
22. ...
23. # 将这些resource加进router中
24. return mapper.collection(collection, resource, **mapper_kwargs)
25. # 遍历 {'network': 'networks', 'subnet': 'subnets','port': 'ports'}
26. # 添加controller
27. for resource in RESOURCES:
28. _map_resource(RESOURCES[resource], resource,
29. attributes.RESOURCE_ATTRIBUTE_MAP.get(
30. RESOURCES[resource], dict()))
31. for resource in SUB_RESOURCES:
32. ...
33. #其实操作和上面一个差不多，

由这个可以看出，添加的controller类型主要分为三类：(其实只要你在neutron目录下grep一下，看哪里调用了create_resource方法即可)

1. OVSNeutronPluginV2
2. extensions/*.py
3. plugins/*.py

针对前两途径加载resource的类，下面慢慢进行描述。至于第三种，则是在各个不同的plugin内部额外实现的，不是必须的。

顺便简单的提一下，在neutron/api/extensions.py下的get_instance方法，这里其实也是和nova一样，是遍历目录下的py文件，来增加extension的

1. ...
2. @classmethod
3. def get_instance(cls):
4. if cls._instance is None:
5. cls._instance = cls(get_extensions_path(),
6. ... NeutronManager.get_service_plugins())

Resource：OVSNeutronPluginV2的实现

看了代码的你肯定知道，OVSNeutronPluginV2这个类，作为core_plugin继承了好多的的类

1. class OVSNeutronPluginV2(db_base_plugin_v2.NeutronDbPluginV2,
2. external_net_db.External_net_db_mixin,
3. extraroute_db.ExtraRoute_db_mixin,
4. l3_gwmode_db.L3_NAT_db_mixin,
5. sg_db_rpc.SecurityGroupServerRpcMixin,
6. l3_agentschedulers_db.L3AgentSchedulerDbMixin,
7. agentschedulers_db.DhcpAgentSchedulerDbMixin,
8. portbindings_db.PortBindingMixin,
9. extradhcpopt_db.ExtraDhcpOptMixin,
10. addr_pair_db.AllowedAddressPairsMixin):

OVSNeutronPluginV2基本上没有什么自己的method，全靠它的"爹们"了。

随便抓两个来看下，比如NeutronDbPluginV2，他的method有get_port,create_network之类的，还有L3_NAT_db_mixin的create_router等。反正与db的操作，OVSNeutronPluginV2是不会管的，都在它的父类那边处理。

再看看OVSNeutronPluginV2继承的这些父类们:

1. #NeutronDbPluginV2继承自NeutronPluginBaseV2
2. class NeutronDbPluginV2(neutron_plugin_base_v2.NeutronPluginBaseV2,
3. CommonDbMixin):
4. class NeutronPluginBaseV2(...) :
5. @abstractmethod
6. def create_subnet(self, context, subnet):
7. @abstractmethod
8. def update_subnet(self, context, id, subnet):
9. @abstractmethod
10. def get_subnet(self, context, id, fields=None):
11. @abstractmethod
12. def get_subnets(self, context, filters=None, fields=None,

其类图如下:(仅展示部分)

基本上可以说有一个接口类(如图中的NeutronPluginBaseV2)，定义了抽象方法，然后一个具体的db类来实现(如NeutronDbPluginV2，这里是采用SQLAlchemy来完成db模型的)

plugin_aware_extension_middleware_factory

在请求进入APIRouter之前，会先经过RequestIdMiddleware（请求header中添加 openstack.request_id）、CatchErrorsMiddleware（错误处理）、keystone权限验证以及 plugin_aware_extension_middleware_factory等几个filter的处理，前三个filter比较直 观，plugin_aware_extension_middleware_factory初始化了Extension目录下的Resource：

class ExtensionMiddleware(wsgi.Middleware):
    """Extensions middleware for WSGI."""

    def __init__(self, application,
                 ext_mgr=None):
        self.ext_mgr = (ext_mgr
                        or ExtensionManager(get_extensions_path()))
        mapper = routes.Mapper()

        # extended resources ext_mgr.get_resources()其实在内部会调用每个extensions目录下的extension类的get_resources方法
        for resource in self.ext_mgr.get_resources():
            path_prefix = resource.path_prefix
            if resource.parent:
                path_prefix = (resource.path_prefix +
                               "/%s/{%s_id}" %
                               (resource.parent["collection_name"],
                                resource.parent["member_name"]))

            LOG.debug(_('Extended resource: %s'),
                      resource.collection)
            for action, method in resource.collection_actions.iteritems():
                conditions = dict(method=[method])
                path = "/%s/%s" % (resource.collection, action)
                with mapper.submapper(controller=resource.controller,
                                      action=action,
                                      path_prefix=path_prefix,
                                      conditions=conditions) as submap:
                    submap.connect(path)
                    submap.connect("%s.:(format)" % path)

            mapper.resource(resource.collection, resource.collection,
                            controller=resource.controller,
                            member=resource.member_actions,
                            parent_resource=resource.parent,
                            path_prefix=path_prefix)

        # extended actions
        action_controllers = self._action_ext_controllers(application,
                                                          self.ext_mgr, mapper)
        for action in self.ext_mgr.get_actions():
            LOG.debug(_('Extended action: %s'), action.action_name)
            controller = action_controllers[action.collection]
            controller.add_action(action.action_name, action.handler)

        # extended requests
        req_controllers = self._request_ext_controllers(application,
                                                        self.ext_mgr, mapper)
        for request_ext in self.ext_mgr.get_request_extensions():
            LOG.debug(_('Extended request: %s'), request_ext.key)
            controller = req_controllers[request_ext.key]
            controller.add_handler(request_ext.handler)

        self._router = routes.middleware.RoutesMiddleware(self._dispatch,
                                                          mapper)
        super(ExtensionMiddleware, self).__init__(application)

比如在extensions下的securitygroup.py中的get_resources方法，看这个代码就知道其中可以处理security_group和security_group_rule两类请求了:

@classmethod
    def get_resources(cls):
        """Returns Ext Resources."""
        my_plurals = [(key, key[:-1]) for key in RESOURCE_ATTRIBUTE_MAP.keys()]
        attr.PLURALS.update(dict(my_plurals))
        exts = []
        plugin = manager.NeutronManager.get_plugin()
        for resource_name in ['security_group', 'security_group_rule']:
            collection_name = resource_name.replace('_', '-') + "s"
            params = RESOURCE_ATTRIBUTE_MAP.get(resource_name + "s", dict())
            quota.QUOTAS.register_resource_by_name(resource_name)
            controller = base.create_resource(collection_name,
                                              resource_name,
                                              plugin, params, allow_bulk=True,
                                              allow_pagination=True,
                                              allow_sorting=True)

            ex = extensions.ResourceExtension(collection_name,
                                              controller,
                                              attr_map=params)
            exts.append(ex)

        return exts

如此，Neutron-Server就已经基本上启动了，无外乎就是加载配置，router各种resource，然后就等待请求了。其中router哪些resource完全是由配置文件来决定的。 当然，在启动的过程中也会初始化db，这也就是为何在安装neutron的时候无需像nova，glance等要执行db sync的原因了。

参考资料

• Neutron网络简介 http://blog.ustack.com/blog/neutron_intro/
• http://www.lnmpy.com/neutron-server-how-to-start/