Python 3.10.1 : Django and channels on Fedora distro - sync and async features.

A consumer is a subclass of either channels.consumer.AsyncConsumer or channels.consumer.SyncConsumer.

Consumers do a couple of things in particular: 

• Structures your code as a series of functions to be called whenever an event happens, rather than making you write an event loop. 
• Allow you to write synchronous or async code and deals with handoffs and threading for you.

This is another tutorial about Django and channels, you can see the first one.

For testing area you need the postman tool and I install and used with snap tool.

[root@fedora mythcat]# dnf install snapd
Last metadata expiration check: 0:40:03 ago on Fri 14 Jan 2022 03:38:55 PM EET.
...
[root@fedora mythcat]# ln -s /var/lib/snapd/snap /snap
[root@fedora mythcat]# snap install postman
2022-01-14T16:22:15+02:00 INFO Waiting for automatic snapd restart...
postman (v9/stable) 9.8.3 from Postman, Inc. (postman-inc✓) installed
[mythcat@fedora ~]$ snap run postman

Let's go on the project folder:

[mythcat@fedora ~]$ cd djangotest001/
[mythcat@fedora djangotest001]$ cd website001/

In this folder I have two folders: appsite001 and website001.

In the appsite001 I add these scripts.

I create a new python script named consumers.py with this source code:

from channels.consumer import SyncConsumer, AsyncConsumer
from channels.exceptions import StopConsumer

class MySyncConsumer(SyncConsumer):
    def websocket_connect(self,event):
        print('Websocket Connected ...')
        self.send({
        'type':'websocket.accept',
        })
    def websocket_receive(self, event):
        print('Messaged Received ...')
        print(event['text'])
        self.send({
        'type':'websocket.send',
        'text':'Message sent to client'
        })
    def websocket_diconnect(self, event):
        print('Websocket Disconnected ...')
        raise StopConsumer
        
class MyAsyncConsumer(AsyncConsumer):
    async def websocket_connect(self,event):
        print('Websocket Connected ...')
    async def websocket_receive(self, event):
        print('Messaged Received ...')
    async def websocket_diconnect(self, event):
        print('Websocket Disconnected ...')

I created routing.py python script with this source code:

from django.urls import path
from . import consumers

websocket_urlpatterns = [
    path('ws/sc/',consumers.MySyncConsumer.as_asgi()),
    ]

In the website001 I change this script named asgi.py.

import os

from django.core.asgi import get_asgi_application

from channels.routing import ProtocolTypeRouter, URLRouter

import appsite001.routing

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'website001.settings')

application = ProtocolTypeRouter({
    'http':get_asgi_application(),
    'websocket':URLRouter(
        appsite001.routing.websocket_urlpatterns
    )
})

Run the Django project with :

[mythcat@fedora website001]$ python manage.py runserver
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).
January 14, 2022 - 15:32:29
Django version 4.0.1, using settings 'website001.settings'
Starting ASGI/Channels version 3.0.4 development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
WebSocket HANDSHAKING /ws/sc/ [127.0.0.1:33944]
Websocket Connected ...
WebSocket CONNECT /ws/sc/ [127.0.0.1:33944]
Messaged Received ...
This is a message from mythcat
...

Use postman tool with websocket to send this message to Django project:

This is a message from mythcat

You can see how this works:

Python 3.10.1 : Django and channels on Fedora distro.

Today I tested the Django version 4.0.1 with channels features on Fedora 35.

For the channels package, I used the pip tool and I install the version

The python package channels come with features like:

Channels augments Django to bring WebSocket, long-poll HTTP, task offloading, and other async support to your code, using familiar Django design patterns and a flexible underlying framework that lets you not only customize behaviors but also write support for your own protocols and needs. see the GitHub website.

Let's install the Django package

[mythcat@fedora ~]$ pip3 install django --user
Requirement already satisfied: django in /usr/local/lib/python3.10/site-packages (4.0.1)
Requirement already satisfied: sqlparse>=0.2.2 in /usr/local/lib/python3.10/site-packages (from django) (0.4.2)
Requirement already satisfied: asgiref<4>=3.4.1 in ./.local/lib/python3.10/site-packages (from django) (3.4.1)

The next step is to create the project named website001:

[mythcat@fedora ~]$ mkdir djangotest001
[mythcat@fedora ~]$ cd djangotest001/
[mythcat@fedora djangotest001]$ django-admin startproject website001
[mythcat@fedora djangotest001]$ cd website001/
[mythcat@fedora website001]$ python3 manage.py runserver
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).

You have 18 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): admin, auth, contenttypes, sessions.
Run 'python manage.py migrate' to apply them.
January 08, 2022 - 13:26:21
Django version 4.0.1, using settings 'website001.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
...

Let's create the application named appsite001:

[mythcat@fedora website001]$ django-admin startapp  appsite001
[mythcat@fedora website001]$ ls
appsite001  db.sqlite3  manage.py  website00

The apps.py file is this:

[mythcat@fedora website001]$ cat  appsite001/apps.py 
from django.apps import AppConfig

class Appsite001Config(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'appsite001'

Let's add this on the settings.py file config:

[mythcat@fedora website001]$ vi website001/settings.py
    
# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'appsite001',
]

Use the migrate feature to fix all:

[mythcat@fedora website001]$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying admin.0003_logentry_add_action_flag_choices... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying auth.0009_alter_user_last_name_max_length... OK
  Applying auth.0010_alter_group_name_max_length... OK
  Applying auth.0011_update_proxy_permissions... OK
  Applying auth.0012_alter_user_first_name_max_length... OK
  Applying sessions.0001_initial... OK

Create the superuser named admin with password admin and set the email address:

[mythcat@fedora website001]$ python manage.py createsuperuser
Username (leave blank to use 'mythcat'): admin
Email address: admin@server.com
Password: 
Password (again): 
The password is too similar to the username.
This password is too short. It must contain at least 8 characters.
This password is too common.
Bypass password validation and create user anyway? [y/N]: y
Superuser created successfully.

http://127.0.0.1:8000/admin/
...

Let's install the channels package for the Django project:

[mythcat@fedora website001]$ pip install channels
...
Successfully installed Automat-20.2.0 autobahn-21.11.1 channels-3.0.4 constantly-15.1.0 

daphne-3.0.2 hyperlink-21.0.0 incremental-21.3.0 pyasn1-0.4.8 pyasn1-modules-0.2.8 

service-identity-21.1.0 twisted-21.7.0 txaio-21.2.1 zope.interface-5.4.0

Add this package into the settinngs.py config file:

[mythcat@fedora website001]$ vi website001/settings.py
INSTALLED_APPS = [
    'channels',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'appsite001',
]
...
#WSGI_APPLICATION = 'website001.wsgi.application'
ASGI_APPLICATION = 'website001.asgi.application'
...

Make these changes to switch from wsgi to asgi features for channels package:

[mythcat@fedora website001]$ cp website001/wsgi.py website001/asgi.py 
[mythcat@fedora website001]$ vi website001/asgi.py 
import os

from django.core.asgi import get_asgi_application
from channels.routing import ProtocolTypeRouter
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'website001.settings')

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

I tested on the admin area how the settings for this packet will work:

[mythcat@fedora website001]$ python3 manage.py runserver
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).
January 08, 2022 - 14:20:53
Django version 4.0.1, using settings 'website001.settings'
Starting ASGI/Channels version 3.0.4 development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
...

The result shows that it works:

The next theoretical steps would be to determine how the channels package will work and routing for access to appsite001.