Async/Await equivalent in C++ version of the library

[majudev]

Hello everyone!

I am struggling to understand how to properly use uWebSockets. I think documentation is a bit lacking. I am trying to offload some of the work to another thread (let's suppose I am transcoding a video in another thread) and I really don't want to block the main thread that is running a webserver. The closest example I found was CRC, however it runs in a blocking fashion because this operation is fast by it's nature.

Below is the code I written to demonstrate what I want to do.

uWS::SSLApp(
        ).post("/data", [&](uWS::HttpResponse<true> * res, uWS::HttpRequest * req){
            std::shared_ptr<std::vector<std::byte>> dataBuffer = std::make_shared<std::vector<std::byte>>(std::vector<std::byte>());

            // Try to read content-length from header
            try{
                const uint64_t contentLength = (uint64_t)std::stoi(std::string(req->getHeader("content-length")));
                if(!contentLength){
                    res->writeStatus("400 Bad Request");
                    res->writeHeader("Content-Type", "application/json");
                    res->write("{\"status\":\"error\",\"message\":\"your request is missing binary data body\"}");
                    res->end();
                    return;
                }
                dataBuffer->reserve(contentLength);
            }catch(...){}

            res->onData([&](std::string_view data, bool last){

                // Lame way to copy data between buffers
                for(unsigned int i = 0; i < data.size(); ++i){
                    dataBuffer->push_back((std::byte)data[i]);
                }

                if(last){
                    // DO SOMETHING IN ANOTHER THREAD
                
                    // after another thread finished, do this
                    res->writeHeader("Content-Type", "application/json");
                    res->end("{\"status\":\"ok\",\"data\":\"some small-sized result from another thread\"}");
                }
            });

            res->onAborted([](){

            });
        }).listen(port, [&port](auto *listen_socket) {
            if (listen_socket) {
                std::cout << "Listening on port " << port << std::endl;
            }
        }).run();

I am not sure how to properly implement it. If I just make std::thread and wait for it, then main thread would still be blocked. I cannot make uWS calls from another thread, as this is not supported (if I understand correctly).

Also, since this transcoding operation can take a few seconds, I think I should send keepalives. Is there a built-in way to do that?

Cheers!

[uNetworkingAB]

Loop::defer is your friend