ReplyT route()

in mcrouter/routes/OutstandingLimitRoute.h [68:143]
70 lines of code
11 McCabe index (conditional complexity)

  ReplyT<Request> route(const Request& req) {
    if (outstanding_ == maxOutstanding_) {
      auto& ctx = fiber_local<RouterInfo>::getSharedCtx();
      auto senderId = ctx->senderId();
      auto& entry = [&]() -> QueueEntry& {
        auto entry_it = senderIdToEntry_.find(senderId);
        if (entry_it != senderIdToEntry_.end()) {
          return *entry_it->second;
        }
        blockedRequests_.push_back(std::make_unique<QueueEntry>(senderId));
        if (senderId) {
          senderIdToEntry_[senderId] = blockedRequests_.back().get();
        }
        return *blockedRequests_.back();
      }();

      auto& stats = ctx->proxy().stats();
      folly::fibers::Baton baton;
      int64_t waitingSince = 0;
      if (carbon::GetLike<Request>::value) {
        ++currentGetReqsWaiting_;
        waitingSince = nowUs();
      } else if (carbon::UpdateLike<Request>::value) {
        ++currentUpdateReqsWaiting_;
        waitingSince = nowUs();
      }
      entry.batons.push_back(&baton);
      baton.wait();
      if (waitingSince > 0) {
        if (carbon::GetLike<Request>::value) {
          stats.increment(
              outstanding_route_get_wait_time_sum_us_stat,
              static_cast<uint64_t>(nowUs() - waitingSince));
          stats.increment(
              outstanding_route_get_reqs_queued_helper_stat,
              currentGetReqsWaiting_);
          --currentGetReqsWaiting_;
          stats.increment(outstanding_route_get_reqs_queued_stat, 1);
        } else if (carbon::UpdateLike<Request>::value) {
          stats.increment(
              outstanding_route_update_wait_time_sum_us_stat,
              static_cast<uint64_t>(nowUs() - waitingSince));
          stats.increment(
              outstanding_route_update_reqs_queued_helper_stat,
              currentUpdateReqsWaiting_);
          --currentUpdateReqsWaiting_;
          stats.increment(outstanding_route_update_reqs_queued_stat, 1);
        }
      }
    } else {
      outstanding_++;
      assert(outstanding_ <= maxOutstanding_);
    }

    SCOPE_EXIT {
      if (!blockedRequests_.empty()) {
        auto entry = std::move(blockedRequests_.front());
        blockedRequests_.pop_front();

        assert(!entry->batons.empty());

        entry->batons.front()->post();
        entry->batons.pop_front();

        if (!entry->batons.empty()) {
          blockedRequests_.push_back(std::move(entry));
        } else {
          senderIdToEntry_.erase(entry->senderId);
        }
      } else {
        outstanding_--;
      }
    };

    return target_->route(req);
  }