Slow performance on localhost + Windows

Hey there,

I am currently hunting for a MQTT OSS Library and also checked out async-mqtt5. Currently I am using paho-mqtt-cpp which has some drawbacks which is why I am looking for alternatives.

General: I love the automatic connection handling but I'd really like some callbacks when no connection can be established to be able to report this to a UI or Logs.

Specific: I run into an issue where on Windows + Localhost with a mosuqitto broker in between the latency is >100ms

Beneath you can find some shortened testing code, this is embeddedin a larger application but (hopefully) shows all the relevant calls.


std::shared_ptr<async_mqtt5::mqtt_client<boost::asio::ip::tcp::socket, std::monostate>> client;

void
requestMessage()
{
  auto cb = [](async_mqtt5::error_code ec,
                                      std::string topic,
                                      std::string payload,
                                      async_mqtt5::publish_props props) {
    // Recv handling here

    requestMessage();
  };

  client->async_receive(cb);
}

int main() {
  boost::asio::io_context ioc;

  client = std::make_shared<async_mqtt5::mqtt_client<boost::asio::ip::tcp::socket>>(ioc);

  std::string clientId = "...";
  client->brokers("127.0.0.1")
    .keep_alive(30)
    .credentials(clientId)
    .async_run(boost::asio::detached);

  auto topics = getTopics();

  client->async_subscribe(topics,
                            async_mqtt5::subscribe_props{},
                            make_safe_callback([this](async_mqtt5::error_code,
                                                      std::vector<async_mqtt5::reason_code>,
                                                      async_mqtt5::suback_props) {
                              requestMessage();
                            }));

// Later
client->async_publish<async_mqtt5::qos_e::exactly_once>(
  topic,
  payload,
  async_mqtt5::retain_e::no,
  async_mqtt5::publish_props{},
  [](async_mqtt5::error_code ec, auto, auto) {
    // Logs errors
  });
}

I use this across two processes with a mosquitto broker in the middle (mosquitto version 2.0.15).

The two processes play ping pong with messages and I measure the time between after the async_publish call until the received handler is called.

Example Payload:

{
  "discriminator": "SomePayload",
  "payload": "This is a message"
}

This comes out to be roughly: 120ms which seems extremely long. Plugging in paho-mqtt-cpp, instead I get around 3ms. On Docker(WSL) I get around 50ms with the mosquitto broker and 15ms with EMQX, this is where paho-mqtt-cpp has issues and reports 100ms. (Same code on both machines, using Clang/MSVC respectively)

Any ideas where this long time could be coming from?

mireo / async-mqtt5

Slow performance on localhost + Windows #17