Django3.0 异步通信初体验(小结)

(venv) D:\work\for_test\django3>pip list
Package  Version

------

asgiref  3.2.3
Django   3.0
pip    10.0.1
pytz    2019.3
setuptools 39.1.0
sqlparse  0.3.0

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.

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:

How to use Django with Daphne
How to use Django with 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 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.

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 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 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)

How to use Django with Daphne
Daphne is a pure-Python ASGI server for UNIX, maintained by members of the Django project. It acts as the reference server for ASGI.

Installing Daphne
You can install Daphne with pip:

python -m pip install daphne
Running Django in Daphne
When Daphne is installed, a daphne command is available which starts the Daphne server process. At its simplest, Daphne needs to be called with the location of a module containing an ASGI application object, followed by what the application is called (separated by a colon).

For a typical Django project, invoking Daphne would look like:

daphne myproject.asgi:application
This will start one process listening on 127.0.0.1:8000. It requires that your project be on the Python path; to ensure that run this command from the same directory as your manage.py file.

Collecting pycparser (from cffi!=1.11.3,>=1.8->cryptography>=2.7->autobahn>=0.18->daphne)
Installing collected packages: idna, hyperlink, zope.interface, attrs, six, Automat, constantly, PyHamcrest, incremental, pycparser, cffi, cry
ptography, pyopenssl, pyasn1, pyasn1-modules, service-identity, twisted, txaio, autobahn, daphne
Successfully installed Automat-0.8.0 PyHamcrest-1.9.0 attrs-19.3.0 autobahn-19.11.1 cffi-1.13.2 constantly-15.1.0 cryptography-2.8 daphne-2.4.
0 hyperlink-19.0.0 idna-2.8 incremental-17.5.0 pyasn1-0.4.8 pyasn1-modules-0.2.7 pycparser-2.19 pyopenssl-19.1.0 service-identity-18.1.0 six-1
.13.0 twisted-19.10.0 txaio-18.8.1 zope.interface-4.7.1

(venv) D:\work\for_test\django3>pip list
Package     Version
---------------- -------
asgiref     3.2.3
attrs      19.3.0
autobahn     19.11.1
Automat     0.8.0
cffi       1.13.2
constantly    15.1.0
cryptography   2.8
daphne      2.4.0
Django      3.0
hyperlink    19.0.0
idna       2.8
incremental   17.5.0
pip       10.0.1
pyasn1      0.4.8
pyasn1-modules  0.2.7
pycparser    2.19
PyHamcrest    1.9.0
pyOpenSSL    19.1.0
pytz       2019.3
service-identity 18.1.0
setuptools    39.1.0
six       1.13.0
sqlparse     0.3.0
Twisted     19.10.0
txaio      18.8.1
zope.interface  4.7.1

(venv) D:\work\for_test\django3>daphne django3.asgi:application
2019-12-04 10:20:07,637 INFO   Starting server at tcp:port=8000:interface=127.0.0.1
2019-12-04 10:20:07,637 INFO   HTTP/2 support not enabled (install the http2 and tls Twisted extras)
2019-12-04 10:20:07,637 INFO   Configuring endpoint tcp:port=8000:interface=127.0.0.1
2019-12-04 10:20:07,637 INFO   Listening on TCP address 127.0.0.1:8000

127.0.0.1:5991 - - [04/Dec/2019:10:30:05] "WSCONNECTING /" - -
2019-12-04 10:30:05,246 ERROR  Exception inside application: Django can only handle ASGI/HTTP connections, not websocket.
 File "d:\work\for_test\django3\venv\lib\site-packages\daphne\cli.py", line 30, in asgi
  await self.app(scope, receive, send)
 File "d:\work\for_test\django3\venv\lib\site-packages\django\core\handlers\asgi.py", line 146, in __call__
  % scope['type']
 Django can only handle ASGI/HTTP connections, not websocket.
127.0.0.1:5991 - - [04/Dec/2019:10:30:05] "WSDISCONNECT /" - -

import django
from django.core.handlers.asgi import ASGIHandler

def get_asgi_application():
  django.setup(set_prefix=False)
  return ASGIHandler()

# Serve only HTTP connections.
# FIXME: Allow to override this.
if scope['type'] != 'http':
  raise ValueError(
    'Django can only handle ASGI/HTTP connections, not %s.'
    % scope['type']
  )