example-in-django-waiting-room-for-asynchronous-tasks/waiting_room/consumers.py

import json
import redis
from django.conf import settings
from channels.generic.websocket import WebsocketConsumer
from asgiref.sync import async_to_sync
from waiting_room.tasks import calculate_min_distance, run_tasks_from_queue, render_location_in_the_queue, notify_of_new_position

class MyConsumer(WebsocketConsumer):

    redis_conn = redis.StrictRedis(host=settings.REDIS_HOST, port=settings.REDIS_PORT, db=0)

    def connect(self):
        self.room_group_name = self.scope["url_route"]["kwargs"]["room_name"]
        async_to_sync(self.channel_layer.group_add)(self.room_group_name, self.channel_name)
        self.accept()
        notify_of_new_position()

    def disconnect(self, close_code):
        async_to_sync(self.channel_layer.group_discard)(self.room_group_name, self.channel_name)
        self.close()

    def receive(self, text_data):
        json_data = json.loads(text_data)
        # Run task
        if json_data['task'] == 'calculate':
            # Check if the new task is already in the queue
            if self.redis_conn.lrange('enqueue', 0, -1).count(self.room_group_name.encode()) == 0:
                # Add the task to the queue
                self.redis_conn.rpush('enqueue', self.room_group_name)
                notify_of_new_position()
                # Send accurate location in the queue
                run_tasks_from_queue()

    def channel_message(self, event):
        message = event['message']

        # Send message to WebSocket
        self.send(text_data=str(message))