lidavidm commented on code in PR #47410:
URL: https://github.com/apache/arrow/pull/47410#discussion_r2297807174
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cpp/src/arrow/flight/transport_server.cc:
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@@ -160,25 +161,63 @@ class TransportMessageReader final : public
FlightMessageReader {
std::shared_ptr<Buffer> app_metadata_;
};
-// TODO(ARROW-10787): this should use the same writer/ipc trick as client
+/// \brief An IpcPayloadWriter for ServerDataStream.
+///
+/// To support app_metadata and reuse the existing IPC infrastructure,
+/// this takes a pointer to a buffer to be combined with the IPC
+/// payload when writing a Flight payload.
+class TransportMessagePayloadWriter : public ipc::internal::IpcPayloadWriter {
+ public:
+ TransportMessagePayloadWriter(ServerDataStream* stream,
+ std::shared_ptr<Buffer>* app_metadata)
+ : stream_(stream), app_metadata_(app_metadata) {}
+
+ Status Start() override { return Status::OK(); }
+ Status WritePayload(const ipc::IpcPayload& ipc_payload) override {
+ FlightPayload payload;
+ payload.ipc_message = ipc_payload;
+
+ if (ipc_payload.type == ipc::MessageType::RECORD_BATCH && *app_metadata_) {
+ payload.app_metadata = std::move(*app_metadata_);
+ }
+ ARROW_ASSIGN_OR_RAISE(auto success, stream_->WriteData(payload));
+ if (!success) {
+ return arrow::Status(arrow::StatusCode::IOError,
+ "Could not write record batch to stream");
+ }
+ return arrow::Status::OK();
+ }
+ Status Close() override {
+ // Closing is handled one layer up in TransportMessageWriter::Close
Review Comment:
Well ideally, we would just expose gRPC and then the server could decide
when it wants to end its output (it can continue reading even after doing so)
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