MQTT性能分析

生产者：

#include 
#include 
#include "mqtt/async_client.h"

const std::string SERVER_ADDRESS = "tcp://broker.example.com:1883";
const std::string CLIENT_ID = "publish_client";
const std::string TOPIC = "test/topic";
const int QOS = 1;

class mqtt_callback : public virtual mqtt::callback {
public:
    void connection_lost(const std::string& cause) override {
        std::cout << "\nConnection lost." << std::endl;
        if (!cause.empty())
            std::cout << "Cause: " << cause << std::endl;
    }

    void delivery_complete(mqtt::delivery_token_ptr token) override {}

};

int main(int argc, char* argv[]) {
    mqtt::async_client client(SERVER_ADDRESS, CLIENT_ID);

    mqtt_callback callback;
    client.set_callback(callback);

    mqtt::connect_options connOpts;
    connOpts.set_clean_session(true);

    try {
        client.connect(connOpts)->wait();

        for (int i = 0; i < 100000; i++)
        {
            std::string message = std::to_string(i);
            mqtt::message_ptr pubmsg = mqtt::make_message(TOPIC, message);
            pubmsg->set_qos(QOS);
            client.publish(pubmsg)->wait();
        }
        
        client.disconnect()->wait();
    }
    catch (const mqtt::exception& exc) {
        std::cerr << "\nError: " << exc.what() << std::endl;
        return 1;
    }

   return 0;
}

测试发现推送数据量比较大的时候，消费端消费的数据不及时。分析：wait()函数是个阻塞函数，会等待服务器返回ack消息后生产者才会往下继续执行，发送下一条指令。使用wireshark抓包可以看出。

临时解决方案：删除wait()函数，不需要等待服务器的ack返回。