Using Django Channels with Redis Streams

Question

I have written a Django application to receive updates of long running tasks. I am using Redis as a channel layer for web-sockets and also making use of Redis Streams to store the updates of the tasks that are currently running. I have spawned a thread from connect method of WebSocket Consumer to run an infinite loop to continuously check for updates from Redis Consumer. This seems to be a hackish solution for what I am trying to achieve i.e. to remain connected to the websocket and also simultaneously receive updates from Redis Streams.

This is my code for Websocket Consumer. As you can see, I am running an infinite loop to check for any new messages in the stream through Redis Consumer.

import json
from threading import Thread

from asgiref.sync import async_to_sync
from channels.generic.websocket import WebsocketConsumer
from django.utils import timezone
from redis import ConnectionPool, Redis
from redis_streams.consumer import Consumer


class ProgressStateConsumer(WebsocketConsumer):
    def __init__(self):
        self.task_id = self.task_group_name = None
        connection_pool = ConnectionPool(
            host="localhost",
            port=6379,
            db=0,
            decode_responses=True,
        )
        self.redis_connection = Redis(connection_pool=connection_pool)
        self.messages = []
        super().__init__()

    def connect(self):
        task_id = self.scope["url_route"]["kwargs"]["task_id"]
        self.task_id = task_id
        self.stream = f"task:{self.task_id}"
        self.task_group_name = (
            f"task-{self.task_id}-{round(timezone.now().timestamp())}"
        )
        async_to_sync(self.channel_layer.group_add)(
            self.task_group_name, self.channel_name
        )
        thread = Thread(target=self.send_status)
        thread.start()
        self.accept()

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

    def receive(self, text_data):
        pass

    def send_status(self):
        consumer = Consumer(
            redis_conn=self.redis_connection,
            stream=self.stream,
            consumer_group=self.task_group_name,
            batch_size=100,
            max_wait_time_ms=500,
        )
        while True:
            items = consumer.get_items()
            for message in items:
                self.messages.append(message.content["message"])
                consumer.remove_item_from_stream(item_id=message.msgid)
            if len(items):
                async_to_sync(self.channel_layer.group_send)(
                    self.task_group_name,
                    {
                        "type": "task_message",
                        "message": self.messages,
                    },
                )

    def task_message(self, event):
        self.send(text_data=json.dumps({"message": event["message"]}))

This seems to be solving my problem but I really needed to know if there is any better solution for achieving this and if running an infinite loop from a thread in the connect method of consumer is the only way I could do it?

Using Django Channels with Redis Streams

0 Answers0