Python - MQTT mulitiple subscription: Which topic the message came from

Question

I have a logger to record all MQTT messages arrive to local broker. This logger have multiple subscriptions, and one of them is "Alerts" - which will additionally send SMS to user's phone ( not showing is attached code ).

My question ( I guess it is a bit newbie ) - but is there a way to filter the origin of a message arrived ?

from sys import path

path.append('/home/guy/.local/lib/python3.5/site-packages')

import paho.mqtt.client as mqtt
from threading import Thread
import datetime
import os


class LogMQTTactivity(Thread):
    def __init__(self, sid=None, mqtt_server="192.168.2.113", username=None, password=None, topics=None, topic_qos=None,
                 filename='/home/guy/MQTTlogger.log'):
        Thread.__init__(self)
        self.sid = sid
        self.mqtt_server = mqtt_server
        self.filename = filename
        self.username = username
        self.password = password
        self.topics = topics
        self.topic_qos = topic_qos
        self.output2screen = 1
        self.client, self.arrived_msg = None, None

        self.check_logfile_valid()
        self.log_header()

    def log_header(self):
        text = ' Connect to following topics '
        x = 12
        self.append_log('*' * x + text + x * "*")
        for topic in self.topics:
            self.append_log(topic)
        self.append_log('*' * 2 * x + len(text) * "*")

    def run(self):
        self.client = mqtt.Client(str(self.sid))
        self.client.on_connect = self.on_connect
        self.client.on_message = self.on_message
        if self.username is not None and self.password is not None:
            self.client.username_pw_set(self.username, self.password)
        self.client.connect(self.mqtt_server, 1883, 60)
        self.client.loop_forever()

    def on_connect(self, client, obj, flags, rc):
        self.append_log(">> Connecting to MQTT mqtt_server %s: %d" % (self.mqtt_server, rc))
        for topic in self.topics:
            self.append_log(">> Subscribe topic: %s" % topic)
            self.client.subscribe(topic, qos=self.topic_qos)

    def on_message(self, client, obj, msg):
        self.arrived_msg = msg.payload.decode()
        self.append_log(self.arrived_msg)

    @staticmethod
    def timeStamp():
        return str(datetime.datetime.now())[:-5]

    def check_logfile_valid(self):
        if os.path.isfile(self.filename) is True:
            self.valid_logfile = True
        else:
            open(self.filename, 'a').close()
            self.valid_logfile = os.path.isfile(self.filename)
            if self.valid_logfile is True:
                msg = '>>Log file %s was created successfully' % self.filename
            else:
                msg = '>>Log file %s failed to create' % self.filename
            print(msg)
            self.append_log(msg)

    def append_log(self, log_entry=''):
        self.msg = '[%s] %s' % (self.timeStamp(), log_entry)

        if self.valid_logfile is True:
            myfile = open(self.filename, 'a')
            myfile.write(self.msg + '\n')
            myfile.close()
        else:
            print('Log err')
        if self.output2screen == 1:
            print(self.msg)


if __name__ == "__main__":
    a = LogMQTTactivity(sid="MQTTlogger", topics=['Alerts', 'notifications'], topic_qos=0,
                        mqtt_server="192.168.2.200", username="guy", password="12345678")
    a.start()

Answer 1

The msg object passed into the on_message callback has a topic field that contains the topic the message was published to.

def on_message(self, client, obj, msg):
    print(msg.topic)
    self.arrived_msg = msg.payload.decode()
    self.append_log(self.arrived_msg)

As mentioned in the doc here