Running scheduled jobs about channels

[mattrasband]

For anyone else coming here and not being sure where to start (like me), a quick example:

# settings.py
CHANNEL_LAYERS = {
    # This is the channel layer id, you can have a bunch if you want
    'default': {
        'BACKEND': 'asgi_redis.RedisChannelLayer',
        'CONFIG': {
            'hosts': [os.environ.get('REDIS_URL', 'redis://localhost:6379')],
        },
        # this defines the router for the layer, e.g. the definitions of channels and their handlers
        'ROUTING': 'app.routing.channel_routing',  
    }
}

# app/routing.py
channel_routing = {
    # You can name your channel anything you want, you probably see 'websocket.*' in most tutorials.
    'your_channel_name': lambda x: print('Channel Triggered Event!'),
}

# ./manage.py shell
from channels import Channel, channel_layers

# default here matches your layer name (from settings.py) that can delegate to your_channel_name
c = Channel('your_channel_name', channel_layer=channel_layers['default'])
c.send({})

Adding a command is pretty simple, see here and then you can just call ./manage.py commandname from cron

[andrewgodwin]

For now, I recommend writing a management command that sends the signals onto the channels, and calling that from cron.

[andrewgodwin]

Yes, the intention is to have some sort of command that can push messages onto channels periodically. In the meantime, I suggest writing a custom management command that does this and calling it using cron.

[erikash]

Thanks, sounds great

[avayo]

Hello Andrew. Thank you for the great project!
Can you (or someone else) suggest the best way to send signals to channels via cron?

[andrewgodwin]

Yup, that's a great example - thanks @mrasband! I'll see if I can work stuff for calling from cron into the docs - it also looks like we're going to have some work start on a scheduled task interface server soon (similar to celerybeat), which might be better if you want things very frequently or can't set cron tasks.

[mattrasband]

Thank you @andrewgodwin for the awesome work, this has helped swing me back to using Django more :)

[andrewgodwin]

I believe @jacobian was looking into it, but I don't know what sort of progress he's made, or if he's found the time to start yet.

[ssteinerx]

You can do it in Twisted in three lines:

from twisted.internet.task import LoopingCall
looper = LoopingCall(send_some_message_function)
looper.start(1)

looper.start(1) will call the function send_some_message_function once every second.

[ssteinerx]

looper.stop()

docs

[JohnDoee]

I went ahead and created a thin wrapper around apscheduler add_job command that'll send a message back on a specified channel when triggered in my own asgi implementation.

It would be simple to squeeze it into Daphne too and solves most, if not all, delayed-call / scheduling issues.

[andrewgodwin]

Closing this as there's delay for channels 1 and in channels 2 you can just use asyncio stuff.