Doing Server-Side Events with Django (hint: it's easy)

views.py

import redis

from django.conf import settings
from django.http import StreamingHttpResponse as HttpResponse

def new_connection():
    """
    At some point this will evolve into using a connection pool,
    but for now it opens a new connection for each user.
    
    """
    return redis.StrictRedis(host=settings.REDIS_HOST,
                             port=settings.REDIS_PORT,
                             db=settings.REDIS_WEBSOCKETS_DB)


def message_iterator(identifier):
    """
    Subscribes to a team channel on Redis and provides an iterator
    to pass published messages back to the client by way of the
    StreamingHttpResponse that is returned to the user below.

    """
    r = new_connection()
    pubsub = r.pubsub()
    pubsub.subscribe(identifier)

    for message in pubsub.listen():
        if message['type'] == 'message':
            # This is critical, data that is sent to the browser needs
            # to look like "data: <payload>\n\n"
            yield "data: %s\n\n" % message['data']


def team_channel(request, identifier=None):
    """
    Replacement for a websocket. Provides a Server-Side event endpoint
    where clients can connect and recieve updates to a team.

    """
    # logic here to validate that the user can access the channel
    # if not request.user.can_access_channel(...)
    #     return 404...

    # The content for the response is an iterator, defined above
    content = message_iterator(identifier)

    # The response (notice import above is StreamingHttpResponse)
    # is created by using the iterator and the special content type.
    response = HttpResponse(content, content_type="text/event-stream")

    # Add an extra header to make sure browsers do not cache the response
    response['Cache-Control'] = 'no-cache'

    # EASY!
    return response