4.0.0 Release Notes

Channels 4 is the next major version of the Channels package. Together with the matching Daphne v4 and channels-redis v4 releases, it updates dependencies, fixes issues, and removes outdated code. It so provides the foundation for Channels development going forward.

In most cases, you can update now by updating channels, daphne, and channels-redis as appropriate, with pip, and by adding daphne at the top of your INSTALLED_APPS setting.

First pip:

pip install -U 'channels[daphne]' channels-redis

Then in your Django settings file:

INSTALLED_APPS = [
    "daphne",
    ...
]

Read on for the details.

Updated Python and Django support

In general Channels will try to follow Python and Django supported versions.

As of release, that means Python 3.7, 3.8, 3.9, and 3.10, as well as Django 3.2, 4.0, and 4.1 are currently supported.

As a note, we reserve the right to drop older Python versions, or the older Django LTS, once the newer one is released, before their official end-of-life if this is necessary to ease development.

Dropping older Python and Django versions will be done in minor version releases, and will not be considered to require a major version change.

The async support in both Python and Django continues to evolve rapidly. We advise you to always upgrade to the latest versions in order to avoid issues in older versions if you’re building an async application.

  • Dropped support for Python 3.6.

  • Minimum Django version is now Django 3.2.

  • Added compatibility with Django 4.1.

Decoupling of the Daphne application server

In order to allow users of other ASGI servers to use Channels without the overhead of Daphne and Twisted, the Daphne application server is now an optional dependency, installable either directly or with the daphne extra, as per the pip example above.

  • Where Daphne is used daphne>=4.0.0 is required. The channels[daphne] extra assures this.

  • The runserver command is moved to the daphne package.

    In order to use the runserver command, add daphne to your INSTALLED_APPS, before django.contrib.staticfiles:

    INSTALLED_APPS = [
    "daphne",
    ...
]

    There is a new system check to ensure this ordering.

    Note, the runworker command remains a part of the channels app.

  • Use of ChannelsLiveServerTestCase still requires Daphne.

Removal of the Django application wrappers

In order to add initial ASGI support to Django, Channels originally provided tools for wrapping your Django application and serving it under ASGI. This included an ASGI handler class, an ASGI HTTP request object, and an ASGI compatible version of the staticfiles handler for use with runserver

Improved equivalents to all of these are what has been added to Django since Django version 3.0. As such serving of Django HTTP applications (whether using sync or async views) under ASGI is now Django’s responsibility, and the matching Channels classes have been removed.

Use of these classes was deprecated in Channels v3 and, if you’ve already moved to the Django equivalents there is nothing further to do.

  • Removed deprecated static files handling in favor of django.contrib.staticfiles.

  • Removed the deprecated AsgiHandler, which wrapped Django views, in favour of Django’s own ASGI support. You should use Django’s get_asgi_application to provide the http handler for ProtocolTypeRouter, or an appropriate path for URLRouter, in order to route your Django application.

  • The supporting AsgiRequest is also removed, as it was only used for AsgiHandler.

  • Removed deprecated automatic routing of http protocol handler in ProtocolTypeRouter. You must explicitly register the http handler in your application if using ProtocolTypeRouter.

The minimal asgi.py file routing the Django ASGI application under a ProtocolTypeRouter will now look something like this:

import os

from channels.routing import ProtocolTypeRouter
from django.core.asgi import get_asgi_application

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'mysite.settings')

application = ProtocolTypeRouter({
    "http": get_asgi_application(),
})

i.e. We use Django’s get_asgi_application(), and explicitly route an http handler for ProtocolTypeRouter. This is merely for illustration of the changes. Please see the docs for more complete examples.

Other changes

  • The use of the guarantee_single_callable() compatibility shim is removed. All applications must be ASGI v3 single-callables.

  • Removed the consumer_started and consumer_finished signals, unused since the 2.0 rewrite.

  • Fixed ChannelsLiveServerTestCase when running on systems using the spawn multiprocessing start method, such as macOS and Windows.