OpenStack Neutron LoadBalance源码解析（一）

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作者：林凯

团队：华为杭州OpenStack团队

     在OpenStack Grizzly版本中，Neutron（当时叫Quantum）组件引入了一个新的网络服务：LoadBalancer（LBaaS），关于LoadBalancer的框架和基础知识方面网上已经有了一些好文章，在此不再赘述。本文将对LoadBalancer的代码流程及实现进行初步解析，肯定会有错误和不严谨的地方，需要大家给予指正。

首先我们来看下我们在创建这些pool、member、healthmonitor和vip的时候，代码都做了哪些事情。

# pool作为LB v1的根对象，是工作流的起点
    def create_pool(self, context, pool):
        provider_name = self._get_provider_name(context, pool['pool'])
        # DB中创建pool对象
        p = super(LoadBalancerPlugin, self).create_pool(context, pool)


        self.service_type_manager.add_resource_association(
            context,
            constants.LOADBALANCER,
            provider_name, p['id'])
        #need to add provider name to pool dict,
        #because provider was not known to db plugin at pool creation
        p['provider'] = provider_name
        driver = self.drivers[provider_name]
        try:
            # 调用默认provider中的驱动创建pool
            driver.create_pool(context, p)
        except loadbalancer.NoEligibleBackend:
            # that should catch cases when backend of any kind
            # is not available (agent, appliance, etc)
            self.update_status(context, ldb.Pool,
                               p['id'], constants.ERROR,
                               "No eligible backend")
            raise loadbalancer.NoEligibleBackend(pool_id=p['id'])
        return p

在neutron.conf中可以看到默认的设置为：

service_provider=LOADBALANCER:Haproxy:neutron.services.loadbalancer.drivers.haproxy.plugin_driver.HaproxyOnHostPluginDriver:default

class HaproxyOnHostPluginDriver(agent_driver_base.AgentDriverBase):
    device_driver = namespace_driver.DRIVER_NAME

def create_pool(self, context, pool):
        # 首先通过agent scheduler分配agent
        agent = self.pool_scheduler.schedule(self.plugin, context, pool,
                                             self.device_driver)
        if not agent:
            raise lbaas_agentscheduler.NoEligibleLbaasAgent(pool_id=pool['id'])
        self.agent_rpc.create_pool(context, pool, agent['host'],
                                   self.device_driver)

def schedule(self, plugin, context, pool, device_driver):
        # 为pool分配一个active的loadbalancer agent，如果其上没有已经使能的agent
        with context.session.begin(subtransactions=True):
            lbaas_agent = plugin.get_lbaas_agent_hosting_pool(
                context, pool['id'])
            if lbaas_agent:
                LOG.debug(_('Pool %(pool_id)s has already been hosted'
                            ' by lbaas agent %(agent_id)s'),
                          {'pool_id': pool['id'],
                           'agent_id': lbaas_agent['id']})
                return
            # 获取active的agent
            active_agents = plugin.get_lbaas_agents(context, active=True)
            if not active_agents:
                LOG.warn(_('No active lbaas agents for pool %s'), pool['id'])
                return


            # 根据device_driver筛选候选的agent
            candidates = plugin.get_lbaas_agent_candidates(device_driver,
                                                           active_agents)
            if not candidates:
                LOG.warn(_('No lbaas agent supporting device driver %s'),
                         device_driver)
                return


            # 随机选取一个合适的候选agent
            chosen_agent = random.choice(candidates)
            # 与pool进行绑定
            binding = PoolLoadbalancerAgentBinding()
            binding.agent = chosen_agent
            binding.pool_id = pool['id']
            context.session.add(binding)
            LOG.debug(_('Pool %(pool_id)s is scheduled to '
                        'lbaas agent %(agent_id)s'),
                      {'pool_id': pool['id'],
                       'agent_id': chosen_agent['id']})
            return chosen_agent

device_driver = namespace_driver.DRIVER_NAME

def create_pool(self, context, pool, driver_name):
        if driver_name not in self.device_drivers:
            LOG.error(_('No device driver on agent: %s.'), driver_name)
            self.plugin_rpc.update_status('pool', pool['id'], constants.ERROR)
            return
        # 获取相应的driver（根据设置默认为HaproxyNSDriver）
        driver = self.device_drivers[driver_name]
        try:
            driver.create_pool(pool)
        except Exception:
            self._handle_failed_driver_call('create', 'pool', pool['id'],
                                            driver.get_name())
        else:
            self.instance_mapping[pool['id']] = driver_name
            # 之后更新数据库中的状态
            self.plugin_rpc.update_status('pool', pool['id'], constants.ACTIVE)

def create_pool(self, pool):
        # nothing to do here because a pool needs a vip to be useful
        # 当没有vip的情况下，不做操作。
        Pass

OpenStack Neutron LoadBalance源码解析（一）

标签：openstack   neutron   网络   源码   

原文地址：http://blog.csdn.net/canxinghen/article/details/42144347