string MQClientAPIImpl::fetchNameServerAddr()

in src/MQClientAPIImpl.cpp [99:170]
65 lines of code
16 McCabe index (conditional complexity)

string MQClientAPIImpl::fetchNameServerAddr(const string& NSDomain) {
  try {
    string homeDir(UtilAll::getHomeDirectory());
    string storePath = homeDir + "/logs/rocketmq-cpp/snapshot";

    boost::filesystem::path dir(storePath);
    boost::system::error_code ec;
    if (!boost::filesystem::exists(dir, ec)) {
      if (!boost::filesystem::create_directory(dir, ec)) {
        LOG_ERROR("create data dir:%s error", storePath.c_str());
        return "";
      }
    }
    string file(storePath);
    string fileBak(storePath);
    vector<string> ret_;
    int retSize = UtilAll::Split(ret_, m_mqClientId, "@");
    if (retSize == 2) {
      file.append("/nameserver_addr-").append(ret_[retSize - 1]);
    } else {
      LOG_ERROR("split mqClientId:%s fail", m_mqClientId.c_str());
      file.append("/nameserver_addr-DEFAULT");
    }
    boost::filesystem::path snapshot_file(file);
    fileBak.append("/nameserver_addr.bak");
    const string addrs = m_topAddressing->fetchNSAddr(NSDomain);
    if (addrs.empty()) {
      if (m_nameSrvAddr.empty()) {
        LOG_INFO("Load the name server snapshot local file:%s", file.c_str());
        if (boost::filesystem::exists(snapshot_file)) {
          ifstream snapshot_file(file, ios::binary);
          istreambuf_iterator<char> beg(snapshot_file), end;
          string filecontent(beg, end);
          updateNameServerAddr(filecontent);
          m_nameSrvAddr = filecontent;
        } else {
          LOG_WARN("The name server snapshot local file not exists");
        }
      }
    } else {
      if (m_firstFetchNameSrv == true) {
        // it is the first time, so need to create the name server snapshot
        // local file
        m_firstFetchNameSrv = false;
      }
      if (addrs.compare(m_nameSrvAddr) != 0) {
        LOG_INFO("name server address changed, old: %s, new: %s", m_nameSrvAddr.c_str(), addrs.c_str());
        updateNameServerAddr(addrs);
        m_nameSrvAddr = addrs;
      } else {
        if (!m_firstFetchNameSrv)
          return m_nameSrvAddr;
      }
      // update the snapshot local file if nameSrv changes or
      // m_firstFetchNameSrv==true
      if (writeDataToFile(fileBak, addrs, true)) {
        if (!UtilAll::ReplaceFile(fileBak, file))
          LOG_ERROR("could not rename bak file:%s", strerror(errno));
      }
    }

    if (!boost::filesystem::exists(snapshot_file)) {
      // the name server snapshot local file maybe deleted by force, create it
      if (writeDataToFile(fileBak, m_nameSrvAddr, true)) {
        if (!UtilAll::ReplaceFile(fileBak, file))
          LOG_ERROR("could not rename bak file:%s", strerror(errno));
      }
    }
  } catch (...) {
  }
  return m_nameSrvAddr;
}