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¶
Install with pip:
pip install django-channels-presence
Add
"channels_presence"
toINSTALLED_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
:
- Observe connections, adding the channel names for each connecting socket to a group.
- Observe disconnections, removing the channel names for each connecting socket from a group.
- 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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