[paho-dev] Throughput of the Paho C library

[Rainer Poisel <rainer.poisel@xxxxxxxxx>]

Hi,

I was just wondering what the throughput of MQTT messages would be
when using the Paho C library. To do so I modified the
synchronous/asynchronous "publish" samples slightly:

In MQTTClient_publish.c:
8<========================
...
while (true)
  {
    MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
    if (MQTTClient_waitForCompletion(client, token, TIMEOUT) !=
MQTTCLIENT_SUCCESS)
    {
      break;
    }

    struct timeval tv;
    gettimeofday(&tv, nullptr);
    std::cout << "Message " << std::setfill(' ') << std::setw(4) <<
cnt << " with delivery token " << std::setfill(' ') << std::setw(4) <<
token <<
        " delivered @ " << tv.tv_sec << "." << std::setfill('0') <<
std::setw(6) << tv.tv_usec << std::endl;
    cnt++;
  }
...
8<========================

In MQTTClient_publish_async.c:
8<========================
...
  while (true)
  {
    MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
    struct timeval tv;
    gettimeofday(&tv, nullptr);
    std::cout << "Message " << std::setfill(' ') << std::setw(4) <<
cnt << " with delivery token " << std::setfill(' ') << std::setw(4) <<
token <<
        " delivered @ " << tv.tv_sec << "." << std::setfill('0') <<
std::setw(6) << tv.tv_usec << std::endl;
    cnt++;
  }
...
8<========================

The maximum number of messages per second I could manage to send using
the Paho library was exactly 10. The bottleneck seems to be in
MQTTClient_yield() in both the synchronous and the asynchronous
approach due to either a call to MQTTClient_sleep() or the do-while
loop.

Before digging deeper into the code: is there any reason for this? I
guess that I simply overlooked something ...

Thanks for any hints,
  Rainer