Build Dynamic Location Tracking Systems in Django with Redis Pub/Sub and Pulsetracker

In this article, we’ll demonstrate how to integrate Pulsetracker's Redis Pub/Sub into a Django application to listen for real-time location updates. Additionally, we'll build a simple JavaScript WebSocket client to send location updates every second to Pulsetracker, showcasing how the service can be utilized in a real-world application.

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Why Django?

Django is a high-level Python web framework that encourages rapid development and clean, pragmatic design. It’s known for its scalability, security, and a rich ecosystem of tools that make building robust web applications faster and easier.

Pulsetracker’s Redis Pub/Sub feature integrates seamlessly with Django, enabling developers to receive and process real-time location data efficiently.

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Setting Up Redis Pub/Sub in Django

1. Install Necessary Packages

First, install Redis support for Django:

pip install django-redis
pip install redis

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2. Configure Redis in Django

Update your settings.py file to include the Pulsetracker Redis connection:

# settings.py

from decouple import config  # Recommended for managing environment variables

# Redis settings
PULSETRACKER_REDIS_URL = config('PULSETRACKER_REDIS_URL', default='redis://redis-sub.pulsestracker.com:6378')

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3. Create a Management Command for the Subscriber

Django management commands are an excellent way to handle long-running background tasks.

Create a new custom command in your Django app:

python manage.py startapp tracker

Inside your app, create the following folder and file structure:

tracker/
    management/
        commands/
            subscribe_pulsetracker.py

Here’s the code for subscribe_pulsetracker.py:

import redis
import hashlib
import hmac
from django.core.management.base import BaseCommand

class Command(BaseCommand):
    help = "Subscribe to Pulsetracker Redis Pub/Sub server"

    def generate_signature(self, app_key, token):
        if "|" not in token:
            raise ValueError("Invalid token format")

        token_hash = hashlib.sha256(token.split("|")[1].encode()).hexdigest()
        return hmac.new(token_hash.encode(), app_key.encode(), hashlib.sha256).hexdigest()

    def handle(self, *args, **options):
        app_key = 'your_app_key_here'
        token = 'your_token_here'
        signature = self.generate_signature(app_key, token)

        channel = f"app:{app_key}.{signature}"
        redis_connection = redis.StrictRedis.from_url('redis://redis-sub.pulsestracker.com:6378')

        print(f"Subscribed to {channel}")
        pubsub = redis_connection.pubsub()
        pubsub.subscribe(channel)

        for message in pubsub.listen():
            if message['type'] == 'message':
                print(f"Received: {message['data'].decode('utf-8')}")

Run the subscriber with:

python manage.py subscribe_pulsetracker

To ensure the subscriber runs continuously in production, use a process manager like Supervisor or Django-Q.

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Using Django-Q for Background Tasks

Install Django-Q:

pip install django-q

Update settings.py:

# settings.py

Q_CLUSTER = {
    'name': 'Django-Q',
    'workers': 4,
    'recycle': 500,
    'timeout': 60,
    'redis': {
        'host': 'redis-sub.pulsestracker.com',
        'port': 6378,
        'db': 0,
    }
}

Create a task to listen to Pulsetracker updates in tasks.py:

from django_q.tasks import async_task
import redis

def pulsetracker_subscribe():
    app_key = 'your_app_key_here'
    token = 'your_token_here'
    channel = f"app:{app_key}.{generate_signature(app_key, token)}"

    redis_connection = redis.StrictRedis.from_url('redis://redis-sub.pulsestracker.com:6378')
    pubsub = redis_connection.pubsub()
    pubsub.subscribe(channel)

    for message in pubsub.listen():
        if message['type'] == 'message':
            print(f"Received: {message['data'].decode('utf-8')}")

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Example WebSocket Client

Here’s a simple JavaScript client that simulates device location updates sent to Pulsetracker via WebSockets:

var wsServer = 'wss://ws-tracking.pulsestracker.com';
var websocket = new WebSocket(wsServer);
const appId = 'YOUR_APP_KEY';
const clientId = 'YOUR_CLIENT_KEY';

websocket.onopen = function(evt) {
    console.log("Connected to WebSocket server.");
    // Send location every 2 seconds
    setInterval(() => {
        if (websocket.readyState === WebSocket.OPEN) {
            navigator.geolocation.getCurrentPosition((position) => {
                console.log(position);
                const locationData = {
                    appId: appId,
                    clientId: clientId,
                    data: {
                        type: "Point",
                        coordinates: [position.coords.longitude, position.coords.latitude]
                    },
                    extra: {
                        key: "value"
                    }
                };


                // Send location data as JSON
                websocket.send(JSON.stringify(locationData));
                console.log('Location sent:', locationData);
            }, (error) => {
                console.error('Error getting location:', error);
            });
        }
    }, 3000); // Every 2 seconds
};

websocket.onclose = function(evt) {
    console.log("Disconnected");
};

websocket.onmessage = function(evt) {
    if (event.data === 'Pong') {
        console.log('Received Pong from server');
    } else {
        // Handle other messages
        console.log('Received:', event.data);
    }
};

websocket.onerror = function(evt, e) {
    console.log('Error occurred: ' + evt.data);
};

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Conclusion

Pulsetracker, combined with Django and Redis Pub/Sub, offers a robust solution for real-time location tracking. This integration allows developers to build scalable, production-ready systems that efficiently handle live location data. The addition of a WebSocket client demonstrates how easily Pulsetracker can integrate into front-end applications, enhancing the user experience.

Try implementing Pulsetracker in your Django project today and share your experience! For more information, visit the Pulsetracker documentation.