首次向Nacos服务进行注册的时候, 回到的回调较慢, 要5秒左右

[huangxinze]

额，解决了：配置项 SUBSCRIPTION_POLL_INTERVAL 未设置

麻烦问一下, 使用该sdk向nacos服务进行注册的时候，首次注册的回调为什么要等大概5秒左右才能收到回调，以下是注册和接收回调的代码:

    nacos::Properties conf;
    conf[nacos::PropertyKeyConst::SERVER_ADDR] = m_strNacosAddressList;
    conf[nacos::PropertyKeyConst::UDP_RECEIVER_PORT] = std::to_string(m_nLocalPort);
    try {
        auto factory = nacos::NacosFactoryFactory::getNacosFactory(conf);
        nacos::ResourceGuard<nacos::INacosServiceFactory> _guardFactory(factory);
        m_pNacosNamingService = factory->CreateNamingService();
    } catch (const nacos::NacosException &e) {
        logW("initialization of nacos naming service failed: " + std::string(e.what()));
        return false;
    }

// setup nacos instance params.
nacos::Instance instance;
instance.ip = m_strLocalIP;
instance.port = m_nLocalPort;
instance.clusterName = "test";
instance.instanceId = "xxxxxxxxxxxxxx";
instance.ephemeral = true;

// regist and subscribe.
try {
    m_pNacosNamingService->registerInstance(strServiceName, instance);
    if (!m_bIsNacosSubscribed) {
        m_bIsNacosSubscribed = true;
        m_pNacosNamingService->subscribe(strServiceName, new NacosEventListener(this));
    }
} catch (const nacos::NacosException &e) {
    logW("registration failed: " + std::string(e.what()));
    return false;
}
return true;

class NacosEventListener : public nacos::EventListener {

public:
NacosEventListener(CCallback*pCallback) {
this->m_pCallback= pCallback;
}

public:
void receiveNamingInfo(const nacos::ServiceInfo &serviceInfo) {
m_pCallback->OnNacosReceiveNamingInfo(serviceInfo);
}

private:
CCallback* m_pCallback;

};