cyber服务发现完全依赖于fastDDS，下面从底层一步一步看下服务发现的整个过程。

topology_manager.cc

首先从这个类看起，这个类是和dds接壤的，dds发现后，完全由这个类接管，然后整体开始通信。

TopologyManager::TopologyManager(): init_(false),node_manager_(nullptr),channel_manager_(nullptr),service_manager_(nullptr),participant_(nullptr),participant_listener_(nullptr) {Init();
}

从上面的构造函数开始分析，除了赋值一些变量，还有就是调用了init函数， 其中node_manager_、channel_manager_、service_manager_是拓扑结构的一些类成员，participant_、participant_listener_很明显就是FAST_RTPS内部的参与者以及监听事件。紧接着进行了init初始化。

init

init函数就是整个topology_manager初始化的过程，下面逐步分析代码。

bool TopologyManager::Init() {if (init_.exchange(true)) {return true;}node_manager_ = std::make_shared<NodeManager>();channel_manager_ = std::make_shared<ChannelManager>();service_manager_ = std::make_shared<ServiceManager>();CreateParticipant();bool result =InitNodeManager() && InitChannelManager() && InitServiceManager();if (!result) {AERROR << "init manager failed.";participant_ = nullptr;delete participant_listener_;participant_listener_ = nullptr;node_manager_ = nullptr;channel_manager_ = nullptr;service_manager_ = nullptr;init_.store(false);return false;}return true;
}

上面首先是创建了三个share_ptr,分别对应NodeManager、ChannelManager、ServiceManager单个类，然后调用CreateParticipant创建participant_。然后对于三个mangger进行了初始化操作，，我们逐步进入分析。

node_manager_ = std::make_shared<NodeManager>();

首先就是上面的代码创建nodemanger，具体要看nodemanger类里面干了啥，所以暂时跳转到nodemanger.cc.

NodeManager、ChannelManager、ServiceManager他们三个都继承了manger类，主要用于记录节点间的关系及节点网络的图结构，紧接着，调用了CreateParticipant函数创建participant，再调用了initNodeMangger去初始化，具体要看函数实现。

CreateParticipant

bool TopologyManager::CreateParticipant() {std::string participant_name =common::GlobalData::Instance()->HostName() + '+' +std::to_string(common::GlobalData::Instance()->ProcessId());participant_listener_ = new ParticipantListener(std::bind(&TopologyManager::OnParticipantChange, this, std::placeholders::_1));participant_ = std::make_shared<transport::Participant>(participant_name, 11511, participant_listener_);return true;
}

这个函数就是使用fastdds的接口创建一个用于全局服务发现的participant，对于cyber的rtps相关的操作，可以看下participant.cc,里面可以看到和rtps官方demo一样的代码，用于通信。participant.cc中官方又封装了一层，然后来初始化和创建participant。

participant

Participant::Participant(const std::string& name, int send_port,eprosima::fastrtps::ParticipantListener* listener): shutdown_(false),name_(name),send_port_(send_port),listener_(listener),fastrtps_participant_(nullptr) {}eprosima::fastrtps::Participant* Participant::fastrtps_participant() {if (shutdown_.load()) {return nullptr;}std::lock_guard<std::mutex> lk(mutex_);if (fastrtps_participant_ != nullptr) {return fastrtps_participant_;}CreateFastRtpsParticipant(name_, send_port_, listener_);return fastrtps_participant_;
}void Participant::CreateFastRtpsParticipant(const std::string& name, int send_port,eprosima::fastrtps::ParticipantListener* listener) {uint32_t domain_id = 80;const char* val = ::getenv("CYBER_DOMAIN_ID");if (val != nullptr) {try {domain_id = std::stoi(val);} catch (const std::exception& e) {AERROR << "convert domain_id error " << e.what();return;}}auto part_attr_conf = std::make_shared<proto::RtpsParticipantAttr>();auto& global_conf = common::GlobalData::Instance()->Config();if (global_conf.has_transport_conf() &&global_conf.transport_conf().has_participant_attr()) {part_attr_conf->CopyFrom(global_conf.transport_conf().participant_attr());}eprosima::fastrtps::ParticipantAttributes attr;attr.rtps.port.domainIDGain =static_cast<uint16_t>(part_attr_conf->domain_id_gain());attr.rtps.port.portBase = static_cast<uint16_t>(part_attr_conf->port_base());attr.rtps.builtin.discovery_config.discoveryProtocol =eprosima::fastrtps::rtps::DiscoveryProtocol_t::SIMPLE;attr.rtps.builtin.discovery_config.m_simpleEDP.use_PublicationWriterANDSubscriptionReader = true;attr.rtps.builtin.discovery_config.m_simpleEDP.use_PublicationReaderANDSubscriptionWriter = true;attr.domainId = domain_id;/*** The user should set the lease_duration and the announcement_period with* values that differ in at least 30%. Values too close to each other may* cause the failure of the writer liveliness assertion in networks with high* latency or with lots of communication errors.*/attr.rtps.builtin.discovery_config.leaseDuration.seconds =part_attr_conf->lease_duration();attr.rtps.builtin.discovery_config.leaseDuration_anno