void Context::connectFullMesh()

in gloo/rendezvous/context.cc [43:115]
53 lines of code
9 McCabe index (conditional complexity)

void Context::connectFullMesh(
    rendezvous::Store& store,
    std::shared_ptr<transport::Device>& dev) {
  std::vector<char> allBytes;
  int localRank = 0;

  // Get Hostname using syscall
  char hostname[HOSTNAME_MAX_SIZE]; // NOLINT
  int rv = gethostname(hostname, HOSTNAME_MAX_SIZE);
  if (rv != 0) {
    throw std::system_error(errno, std::system_category());
  }

  auto localHostName = std::string(hostname);
  // Add global rank <> hostname pair to the Store. This store is then passed
  // to Gloo when connectFullMesh is called, where Gloo uses the global rank <>
  // hostname mapping to compute local ranks.
  std::string localKey("rank_" + std::to_string(rank));
  const std::vector<char> value(localHostName.begin(), localHostName.end());
  store.set(localKey, value);

  for (int i = 0; i < size; i++) {
    if (i == rank) {
      break;
    }

    std::string key("rank_" + std::to_string(i));
    auto val = store.get(key);
    auto hostName = std::string((const char*)val.data(), val.size());

    if (hostName == localHostName) {
      localRank++;
    }
  }

  // Create pairs
  auto transportContext = dev->createContext(rank, size);
  transportContext->setTimeout(getTimeout());
  for (int i = 0; i < size; i++) {
    if (i == rank) {
      continue;
    }

    auto& pair = transportContext->createPair(i);
    pair->setLocalRank(localRank);
    auto addrBytes = pair->address().bytes();
    allBytes.insert(allBytes.end(), addrBytes.begin(), addrBytes.end());
  }

  std::ostringstream storeKey;
  storeKey << rank;
  store.set(storeKey.str(), allBytes);

  // Connect every pair
  for (int i = 0; i < size; i++) {
    if (i == rank) {
      continue;
    }

    // Wait for address of other side of this pair to become available
    std::ostringstream key;
    key << i;
    store.wait({key.str()}, getTimeout());

    // Connect to other side of this pair
    auto allAddrs = store.get(key.str());
    auto addr = extractAddress(allAddrs, i);
    transportContext->getPair(i)->connect(addr);
  }

  device_ = dev;
  transportContext_ = std::move(transportContext);
}