django/docs/howto/deployment/asgi/index.txt

=======================
How to deploy with ASGI
=======================

As well as WSGI, Django also supports deploying on ASGI_, the emerging Python
standard for asynchronous web servers and applications.

.. _ASGI: https://asgi.readthedocs.io/en/latest/

Django's :djadmin:`startproject` management command sets up a default ASGI
configuration for you, which you can tweak as needed for your project, and
direct any ASGI-compliant application server to use.

Django includes getting-started documentation for the following ASGI servers:

.. toctree::
   :maxdepth: 1

   daphne
   uvicorn

The ``application`` object
==========================

Like WSGI, ASGI has you supply an ``application`` callable which
the application server uses to communicate with your code. It's commonly
provided as an object named ``application`` in a Python module accessible to
the server.

The :djadmin:`startproject` command creates a file
:file:`<project_name>/asgi.py` that contains such an ``application`` callable.

It's not used by the development server (``runserver``), but can be used by
any ASGI server either in development or in production.

ASGI servers usually take the path to the application callable as a string;
for most Django projects, this will look like ``myproject.asgi:application``.

.. warning::

    While Django's default ASGI handler will run all your code in a synchronous
    thread, if you choose to run your own async handler you must be aware of
    async-safety.

    Do not call blocking synchronous functions or libraries in any async code.
    Django prevents you from doing this with the parts of Django that are not
    async-safe, but the same may not be true of third-party apps or Python
    libraries.

Configuring the settings module
===============================

When the ASGI server loads your application, Django needs to import the
settings module — that's where your entire application is defined.

Django uses the :envvar:`DJANGO_SETTINGS_MODULE` environment variable to locate
the appropriate settings module. It must contain the dotted path to the
settings module. You can use a different value for development and production;
it all depends on how you organize your settings.

If this variable isn't set, the default :file:`asgi.py` sets it to
``mysite.settings``, where ``mysite`` is the name of your project.

Applying ASGI middleware
========================

To apply ASGI middleware, or to embed Django in another ASGI application, you
can wrap Django's ``application`` object in the ``asgi.py`` file. For example::

    from some_asgi_library import AmazingMiddleware
    application = AmazingMiddleware(application)