How does Django Channels Group/channel_session work?

user2218780 Published at Dev

user2218780

It seems Group and channel_session can persist across multiple message sessions and consumers. How does Channels achieve that?

@channel_session_user_from_http
def ws_connect(message):
    # Add them to the right group
    message.channel_session['room'] = 'room name'
    Group("chat-%s" % message.user.username[0]).add(message.reply_channel)

@channel_session_user
def ws_disconnect(message):
    if 'room' in message.channel_session:
        print('room====', message.channel_session['room'])
    Group("chat-%s" % message.user.username[0]).discard(message.reply_channel)

I would like to setup a long existing object, much like a global object which is accessible by every consumer.

Nick Sweeting

You can use @channel_session (or the @channel_session_user) decorator to achieve this. Make sure your object is serializable, then just add it to the user's channel session like this:

@channel_session_user_from_http
def ws_connect(message):
    message.session.myobject = {'test': True}

@channel_session_user
def ws_connect(message):
    print(message.session.myobject)   # should output {'test': True}

Alternatively, just use your DB or redis to persist things like you would normally in Django:

@channel_session_user_from_http
def ws_connect(message):
    redis_conn.set('my-persisted-key', "{'test': True}")

@channel_session_user
def ws_connect(message):
    print(redis_conn.get('my-persisted-key'))  # should output "{'test': True}"

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