django-channels-presence

django-channels-presence is a Django app which adds “rooms” and presence notification capability to a Django application using django-channels. If you’re building a chat room or other site that needs to keep track of “who is connected right now”, this might be useful to you.

Quick install

  1. Install with pip:

    pip install django-channels-presence

  2. Add "channels_presence" to INSTALLED_APPS:

    # proj/settings.py

INSTALLED_APPS = [
    ...
    "channels_presence",
    ...
]

Upgrading

Django Channels v2 is a major backwards-incompatible change from Django Channels v1; and hence the latest django-channels-presence is not compatible with older versions of django-channels.

If you’re using:

  • django-channels v1.x: Use django-channels-presence v0.
  • django-channels v2.x: Use django-channels-presence v1+.

Code that uses django-channels-presence v0 or django-channels v1 will need to be rewritten to target channel layers, consumers, and other new concepts from django-channels v2.

Motivation

This application builds on top of django-channels. You should have a good understanding of how it works before diving in here. To enable groups and messaging by channel name, django-channels-presence requires that the optional “channel layers” feature of django-channels v2 be used.

There are 3 main tasks that need to be accomplished in order to track “presence” in rooms using django-channels:

  1. Observe connections, adding the channel names for each connecting socket to a group.
  2. Observe disconnections, removing the channel names for each connecting socket from a group.
  3. Prune channel names from groups after they go stale. We won’t always get a socket disconnect event when a socket drops off; so we need to use heartbeats and a periodic pruning task to remove stale connections.

django-channels-presence provides database models and helpers to handle each of these tasks. This implementation makes database queries on every connection, disconnection, and message, as well as periodic queries to prune stale connections. As a result, it will scale differently than django-channels alone.

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