void HaskellAsyncProcessor::processSerializedRequest()

in server/cpp/HaskellProcessor.cpp [21:150]
103 lines of code
16 McCabe index (conditional complexity)

void HaskellAsyncProcessor::processSerializedRequest(
    ResponseChannelRequest::UniquePtr req,
    apache::thrift::SerializedRequest&& serializedRequest,
    protocol::PROTOCOL_TYPES protType,
    Cpp2RequestContext* context,
    folly::EventBase* eb,
    concurrency::ThreadManager* tm) {
  // General note: we only want communicate (via req->sendReply or
  // req->sendErrorWrapped) and destroy req on eb's thread. We assume that we
  // are on eb's thread now but the EventTask that we create further below won't
  // necessarily be.

  // Immediately give reply to one-way calls
  bool oneway = oneways_.find(context->getMethodName()) != oneways_.end();
  if (oneway && !req->isOneway()) {
    req->sendReply(ResponsePayload{});
  }

  // Adds a request handler to the thrift queue.
  apache::thrift::LegacyRequestExpiryGuard rh{std::move(req), eb};
  auto task = [context,
               oneway,
               cb = callback_,
               legacySerializedRequest =
                   apache::thrift::LegacySerializedRequest(
                       protType,
                       context->getProtoSeqId(),
                       context->getMethodName(),
                       std::move(serializedRequest)),
               rh = std::move(rh)]() mutable {
    // Mark the request as processing, so that it won't be failed
    // with a queue timeout.
    auto req = std::move(rh.req);
    if (req && !req->getShouldStartProcessing()) {
      // Queue timeout must have occurred. Clean up request and return.
      HandlerCallbackBase::releaseRequest(std::move(req), rh.eb);
      return;
    }

    // EventTask only calles us if oneway || req->isActive()
    // Receive all the bytes and create a single buffer
    folly::ByteRange input_range = legacySerializedRequest.buffer->coalesce();
    auto input_data = input_range.data();
    auto input_len = input_range.size();

    // Send the bytes to Haskell and get the return bytes back
    TResponse response;
    (*cb)(
        context->getHeader()->getProtocolId(),
        input_data,
        input_len,
        &response);
    std::unique_ptr<uint8_t[], decltype(free)*> output_str(response.data, free);
    SCOPE_EXIT {
      free(response.ex_name);
      free(response.ex_text);
    };
    if (response.ex_name) {
      auto header = context->getHeader();
      header->setHeader(
          kUex, std::string(response.ex_name, response.ex_name_len));
      if (response.ex_text) {
        header->setHeader(
            kUexw, std::string(response.ex_text, response.ex_text_len));
      }
      header->setHeader(
          kEx,
          response.client_error ? kAppClientErrorCode : kAppServerErrorCode);
    }

    if (!oneway && req && req->isActive()) {
      apache::thrift::MessageType mtype;
      apache::thrift::ResponsePayload payload;
      try {
        // Take ownership of the output bytes into an IOBuf
        auto outbuf =
            folly::IOBuf::takeOwnership(std::move(output_str), response.len);

        // Send the output bytes along
        apache::thrift::LegacySerializedResponse legacySerializedResponse{
            std::move(outbuf)};
        std::tie(mtype, payload) =
            std::move(legacySerializedResponse)
                .extractPayload(
                    req->includeEnvelope(),
                    context->getHeader()->getProtocolId(),
                    context->getProtoSeqId());
        payload.transform(context->getHeader()->getWriteTransforms());
      } catch (const std::exception& e) {
        if (!oneway) {
          const auto s = e.what();
          rh.eb->runInEventBaseThread([req = std::move(req), s]() mutable {
            req->sendErrorWrapped(
                folly::make_exception_wrapper<TApplicationException>(
                    TApplicationException::TApplicationExceptionType::
                        INTERNAL_ERROR,
                    folly::to<std::string>(
                        "Failed to read response from Haskell: ", s)),
                "haskell");
          });
        }
        return;
      }
      rh.eb->runInEventBaseThread([mtype = mtype,
                                   req = std::move(req),
                                   payload = std::move(payload)]() mutable {
        if (mtype == apache::thrift::MessageType::T_EXCEPTION) {
          req->sendException(std::move(payload));
        } else {
          req->sendReply(std::move(payload));
        }
      });
    }

    // either is inactive or oneway method, simply delete req in eb thread
    if (req) {
      rh.eb->runInEventBaseThread([req = std::move(req)] {});
    }
  };

  const auto pri = apache::thrift::concurrency::NORMAL;
  const auto source =
      apache::thrift::concurrency::ThreadManager::Source::UPSTREAM;
  // the ThreadManager can prioritise upstream jobs differently
  // from internal jobs. This also affects certain metrics, such
  // as thrift.queued_requests which only counts upstream jobs on
  // the queue.
  auto ka = tm->getKeepAlive(pri, source);
  ka->add(std::move(task));
}