Paho-Mqtt django, on_message() function runs twice

I am using paho-mqtt in django to recieve messages. Everything works fine. But the on_message() function is executed twice.

I tried Debugging, but it seems like the function is called once, but the database insertion is happening twice, the printing of message is happening twice, everything within the on_message() function is happening twice, and my data is inserted twice for each publish.

I doubted it is happening in a parallel thread, and installed a celery redis backend to queue the insertion and avoid duplicate insertions. but still the data is being inserted twice.

I also tried locking the variables, to avoid problems in parallel threading, but still the data is inserted twice.

I am using Postgres DB

How do I solve this issue? I want the on_message() function to execute only once for each publish

my init.py

from . import mqtt  
mqtt.client.loop_start()

my mqtt.py

import ast
import json

import paho.mqtt.client as mqtt


# Broker CONNACK response
from datetime import datetime

from raven.utils import logger

from kctsmarttransport import settings


def on_connect(client, userdata, flags, rc):
    # Subcribing to topic and recoonect for
    client.subscribe("data/gpsdata/server/#")
    print 'subscribed to data/gpsdata/server/#'


# Receive message

def on_message(client, userdata, msg):
    # from kctsmarttransport.celery import bus_position_insert_task
    # bus_position_insert_task.delay(msg.payload)
    from Transport.models import BusPosition
    from Transport.models import Student, SpeedWarningLog, Bus
    from Transport.models import Location
    from Transport.models import IdleTimeLog
    from pytz import timezone
    try:
        dumpData = json.dumps(msg.payload)
        rawGpsData = json.loads(dumpData)
        jsonGps = ast.literal_eval(rawGpsData)
        bus = Bus.objects.get(bus_no=jsonGps['Busno'])
        student = None
        stop = None
        if jsonGps['card'] is not False:
            try:
                student = Student.objects.get(rfid_value=jsonGps['UID'])
            except Student.DoesNotExist:
                student = None
        if 'stop_id' in jsonGps:
            stop = Location.objects.get(pk=jsonGps['stop_id'])

        dates = datetime.strptime(jsonGps['Date&Time'], '%Y-%m-%d %H:%M:%S')
        tz = timezone('Asia/Kolkata')
        dates = tz.localize(dates)
        lat = float(jsonGps['Latitude'])
        lng = float(jsonGps['Longitude'])
        speed = float(jsonGps['speed'])

        # print msg.topic + " " + str(msg.payload)
        busPosition = BusPosition.objects.filter(bus=bus, created_at=dates,
                                                 lat=lat,
                                                 lng=lng,
                                                 speed=speed,
                                                 geofence=stop,
                                                 student=student)
        if busPosition.count() == 0:
            busPosition = BusPosition.objects.create(bus=bus, created_at=dates,
                                                     lat=lat,
                                                     lng=lng,
                                                     speed=speed,
                                                     geofence=stop,
                                                     student=student)
            if speed > 60:
                SpeedWarningLog.objects.create(bus=busPosition.bus, speed=busPosition.speed,
                                               lat=lat, lng=lng, created_at=dates)
                sendSMS(settings.TRANSPORT_OFFICER_NUMBER, jsonGps['Busno'], jsonGps['speed'])
            if speed <= 2:
                try:
                    old_entry_query = IdleTimeLog.objects.filter(bus=bus, done=False).order_by('idle_start_time')
                    if old_entry_query.count() > 0:
                        old_entry = old_entry_query.reverse()[0]
                        old_entry.idle_end_time = dates
                        old_entry.save()
                    else:
                        new_entry = IdleTimeLog.objects.create(bus=bus, idle_start_time=dates, lat=lat, lng=lng)
                except IdleTimeLog.DoesNotExist:
                    new_entry = IdleTimeLog.objects.create(bus=bus, idle_start_time=dates, lat=lat, lng=lng)
            else:
                try:
                    old_entry_query = IdleTimeLog.objects.filter(bus=bus, done=False).order_by('idle_start_time')
                    if old_entry_query.count() > 0:
                        old_entry = old_entry_query.reverse()[0]
                        old_entry.idle_end_time = dates
                        old_entry.done = True
                        old_entry.save()
                except IdleTimeLog.DoesNotExist:
                    pass
    except Exception, e:
        logger.error(e.message, exc_info=True)


client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect("10.1.75.106", 1883, 60)