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

class APIRouter(wsgi.Router):
# 一个工厂类方法
@classmethod
def factory(cls, global_config, **local_config):
return cls(**local_config)
# 真正调用的实例化方法
def __init__(self, **local_config):
...
#获取NeutornManage的core_plugin，这个定义在/etc/neutron/neutron.conf,比如我的是
#core_plugin = neutron.plugins.openvswitch.ovs_neutron_plugin.OVSNeutronPluginV2
plugin = manager.NeutronManager.get_plugin()
#扫描特定路径下的extensions
ext_mgr = extensions.PluginAwareExtensionManager.get_instance()
...
#定义的局部方法
def _map_resource(collection, resource, params, parent=None):
...
controller = base.create_resource(
collection, resource, plugin, params, allow_bulk=allow_bulk,
parent=parent, allow_pagination=allow_pagination,
allow_sorting=allow_sorting)
...
# 将这些resource加进router中
return mapper.collection(collection, resource, **mapper_kwargs)
# 遍历 {'network': 'networks', 'subnet': 'subnets','port': 'ports'}
# 添加controller
for resource in RESOURCES:
_map_resource(RESOURCES[resource], resource,
attributes.RESOURCE_ATTRIBUTE_MAP.get(
RESOURCES[resource], dict()))
for resource in SUB_RESOURCES:
...
#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)

OVSNeutronPluginV2
extensions/*.py
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

...
@classmethod
def get_instance(cls):
if cls._instance is None:
cls._instance = cls(get_extensions_path(),
... 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

class OVSNeutronPluginV2(db_base_plugin_v2.NeutronDbPluginV2,
external_net_db.External_net_db_mixin,
extraroute_db.ExtraRoute_db_mixin,
l3_gwmode_db.L3_NAT_db_mixin,
sg_db_rpc.SecurityGroupServerRpcMixin,
l3_agentschedulers_db.L3AgentSchedulerDbMixin,
agentschedulers_db.DhcpAgentSchedulerDbMixin,
portbindings_db.PortBindingMixin,
extradhcpopt_db.ExtraDhcpOptMixin,
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:

#NeutronDbPluginV2继承自NeutronPluginBaseV2
class NeutronDbPluginV2(neutron_plugin_base_v2.NeutronPluginBaseV2,
CommonDbMixin):
class NeutronPluginBaseV2(...) :
@abstractmethod
def create_subnet(self, context, subnet):
@abstractmethod
def update_subnet(self, context, id, subnet):
@abstractmethod
def get_subnet(self, context, id, fields=None):
@abstractmethod
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/