如何使用 ASGI 来部署¶
同 WSGI 一样，Django 也支持使用 ASGI 来部署，它是为了支持异步网络服务器和应用而新出现的 Python 标准。
Django's 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:
application 对象¶
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 startproject command creates a 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.
警告
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.
配置 settings 模块¶
When the ASGI server loads your application, Django needs to import the settings module — that's where your entire application is defined.
Django 利用 DJANGO_SETTINGS_MODULE 环境变量来定位合适的配置模块。它必须包含到配置模块的点式路径。开发环境和生产环境可以配置不同值；这都取决于你是如何组织配置的。
If this variable isn't set, the default 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)
