Python Channels库使用

Channels 聊天室

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 2020/09/04   Share

前言

记录一下django channels 库的基本使用
本文档记录官方文档教程,可直接参考官方文档：教程第一部分

基本设置

创建聊天室应用

代码结构如下图

添加我们的chatroom应用. 编辑djangoProject/settings.py文件, 在列表中加入我们的APP名称

# Application definition

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

添加索引视图

在应用下下建立一个templates/chatroom/index.html 文件。

<!-- chatroom/templates/chatroom/index.html -->
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <title>Chat Rooms</title>
</head>
<body>
    What chat room would you like to enter?<br>
    <input id="room-name-input" type="text" size="100"><br>
    <input id="room-name-submit" type="button" value="Enter">

    <script>
        document.querySelector('#room-name-input').focus();
        document.querySelector('#room-name-input').onkeyup = function(e) {
            if (e.keyCode === 13) {  // enter, return
                document.querySelector('#room-name-submit').click();
            }
        };

        document.querySelector('#room-name-submit').onclick = function(e) {
            var roomName = document.querySelector('#room-name-input').value;
            window.location.pathname = '/chat/' + roomName + '/';
        };
    </script>
</body>
</html>

创建一个view视图 chatroom/views.py

from django.shortcuts import render

# Create your views here.


def index(request):
    return render(request, 'chatroom/index.html')

配置url路径,在项目目录下创建urls.py

from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

将根URLconf指向我们的 urls.py

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('chat/', include('chatroom.urls'))
]

验证配置是否有效

1	python3 manage.py runserver

使用 Channels 库

安装channels

1	python -m pip install -U channels

Channels 也要创建一个路由配置, 配置类似于django的url_conf，它告诉channels当channels服务器接收到HTTP请求时要运行什么代码、

首先在django url跟路由目录下同级，创建一个channels的根路由 djangoProject/routing.py

from channels.routing import ProtocolTypeRouter

application = ProtocolTypeRouter({
    # (http->django views is added by default)
})

将channels添加到 INSTALLED_APPS 配置

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

还需要继续修改settings 将channels指向根路由配置，在配置中添加

1 2	# Channels ASGI_APPLICATION = 'djangoProject.routing.application'

此时，重新运行下方命令，已确认channels正常工作

1	python3 manage.py runserver

可以看到如下输出

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.
September 04, 2020 - 14:11:57
Django version 3.1.1, using settings 'djangoProject.settings'
Starting ASGI/Channels version 2.4.0 development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.

注意此行,表示channels开发服务器已接管django的开发服务器

Starting ASGI/Channels version 2.4.0 development server at http://127.0.0.1:8000/

实现聊天服务器

新建房间的前端页面 chatroom/templates/room.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <title>Chat Room</title>
</head>
<body>
    <textarea id="chat-log" cols="100" rows="20"></textarea><br>
    <input id="chat-message-input" type="text" size="100"><br>
    <input id="chat-message-submit" type="button" value="Send">
    {{ room_name|json_script:"room-name" }}
    <script>
        const roomName = JSON.parse(document.getElementById('room-name').textContent);

        const chatSocket = new WebSocket(
            'ws://'
            + window.location.host
            + '/ws/chat/'
            + roomName
            + '/'
        );

        chatSocket.onmessage = function(e) {
            const data = JSON.parse(e.data);
            document.querySelector('#chat-log').value += (data.message + '\n');
        };

        chatSocket.onclose = function(e) {
            console.error('Chat socket closed unexpectedly');
        };

        document.querySelector('#chat-message-input').focus();
        document.querySelector('#chat-message-input').onkeyup = function(e) {
            if (e.keyCode === 13) {  // enter, return
                document.querySelector('#chat-message-submit').click();
            }
        };

        document.querySelector('#chat-message-submit').onclick = function(e) {
            const messageInputDom = document.querySelector('#chat-message-input');
            const message = messageInputDom.value;
            chatSocket.send(JSON.stringify({
                'message': message
            }));
            messageInputDom.value = '';
        };
    </script>
</body>
</html>

创建对应的视图views.py

from django.shortcuts import render

# Create your views here.


def index(request):
    return render(request, 'chatroom/index.html')


def room(request, room_name):
    return render(request, 'chatroom/room.html', {
        'room_name': room_name
    })

创建url规则

from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
    path('<str:room_name>/', views.room, name='room')
]

重新运行页面，并键入房间名,F12打开console发现报错

1	WebSocket connection to 'ws://127.0.0.1:8000/ws/chat/3232/' failed: Error during WebSocket handshake: net::ERR_CONNECTION_RESET

这是因为我们还未创建接受WebSocket连接的使用者。

创建消费者

在app目录下创建 chatroom/consumers.py

import json
from channels.generic.websocket import WebsocketConsumer


class ChatConsumer(WebsocketConsumer):
    def connect(self):
        self.accept()

    def disconnect(self, close_code):
        pass

    def receive(self, text_data):
        text_data_json = json.loads(text_data)
        message = text_data_json['message']

        self.send(text_data=json.dumps({
            'message': message
        }))

创建URL匹配规则,chatroom/routing.py

为了规范,一般匹配 ws 路径前缀

from django.urls import re_path

from . import consumers

websocket_urlpatterns = [
    re_path(r'ws/chat/(?P<room_name>\w+)/$', consumers.ChatConsumer),
]

将匹配规则导入主路由匹配 djangoProject/routing.py

from channels.auth import AuthMiddlewareStack
from channels.routing import ProtocolTypeRouter, URLRouter
import chatroom.routing

application = ProtocolTypeRouter({
    # (http->django views is added by default)
    'websocket': AuthMiddlewareStack(
        URLRouter(
            chatroom.routing.websocket_urlpatterns
        )
    ),
})

此配置指定在与Channels服务器建立连接时，ProtocolTypeRouter 将会检查连接的类型。如果是WebSocket连接(ws:// 或者 wss://), 则将连接给配给AuthMiddlewareStack.

经过鉴权以后,连接到URL路径

现在打开聊天室,便可以在窗口中看到自己的消息，但是无法看到另一个相同窗口所发送的聊天内容。

所以，我们需要相同的consumer能够互相通信才行, channels提供了一个 channel layer 来管理

使用 channels layer

官方推荐使用redis作为后端存储

安装 channels_redis

1	python3 -m pip install channels_redis

在使用layer前,需要在配置文件中添加Redis设置

# Channels
ASGI_APPLICATION = 'djangoProject.routing.application'
CHANNEL_LAYERS = {
    'default': {
        'BACKEND': 'channels_redis.core.RedisChannelLayer',
        'CONFIG': {
            "hosts": [('192.168.1.70', 6379)],
        },
    },
}

为了检测可用，我们需要打开django shell 并执行如下命令

python3 manage.py shell
>>> import channels.layers
>>> channel_layer = channels.layers.get_channel_layer()
>>> from asgiref.sync import async_to_sync
>>> async_to_sync(channel_layer.send)('test_channel', {'type': 'hello'})
>>> async_to_sync(channel_layer.receive)('test_channel')
{'type': 'hello'}

使用新的代码来替换 consumers.py

import json
from asgiref.sync import async_to_sync
from channels.generic.websocket import WebsocketConsumer

class ChatConsumer(WebsocketConsumer):
    def connect(self):
        self.room_name = self.scope['url_route']['kwargs']['room_name']
        self.room_group_name = 'chat_%s' % self.room_name

        # Join room group
        async_to_sync(self.channel_layer.group_add)(
            self.room_group_name,
            self.channel_name
        )

        self.accept()

    def disconnect(self, close_code):
        # Leave room group
        async_to_sync(self.channel_layer.group_discard)(
            self.room_group_name,
            self.channel_name
        )

    # Receive message from WebSocket
    def receive(self, text_data):
        text_data_json = json.loads(text_data)
        message = text_data_json['message']

        # Send message to room group
        async_to_sync(self.channel_layer.group_send)(
            self.room_group_name,
            {
                'type': 'chat_message',
                'message': message
            }
        )

    # Receive message from room group
    def chat_message(self, event):
        message = event['message']

        # Send message to WebSocket
        self.send(text_data=json.dumps({
            'message': message
        }))

新的代码我们需要进行一步说明

self.scope['url_route']['kwargs']['room_name']

room_name是从 chatroom/routing.py 的URL路由中获取的参数.scope对象完整内容如下

{'type': 'websocket', 'path': '/ws/chat/3232/', 'raw_path': b'/ws/chat/3232/', 'headers': [(b'host', b'127.0.0.1:8000'), (b'connection', b'Upgrade'), (b'pragma', b'no-cache'), (b'cache-control', b'no-cache'), (b'user-agent', b'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.88 Safari/537.36'), (b'upgrade', b'websocket'), (b'origin', b'http://127.0.0.1:8000'), (b'sec-websocket-version', b'13'), (b'accept-encoding', b'gzip, deflate, br'), (b'accept-language', b'zh-CN,zh;q=0.9,en-US;q=0.8,en;q=0.7'), (b'cookie', b'csrftoken=NVTSIc1SysiRUeOjW2IYuAQo9QMbyEPLofdqJA4jdLBkraImmCPP3jdScaNyXzsZ'), (b'sec-websocket-key', b'fOBE+s7uCP0NQdycxwRNvQ=='), (b'sec-websocket-extensions', b'permessage
  -deflate; client_max_window_bits')], 'query_string': b'', 'client': ['127.0.0.1', 57962], 'server': ['127.0.0.1', 8000], 'subprotocols': [], 'cookies': {'csrftoken': 'NVTSIc1SysiRUeOjW2
  IYuAQo9QMbyEPLofdqJA4jdLBkraImmCPP3jdScaNyXzsZ'}, 'session': <django.utils.functional.LazyObject object at 0x000001D8CAA88E80>, 'user': <channels.auth.UserLazyObject object at 0x000001D
  8CAA88EF0>, 'path_remaining': '', 'url_route': {'args': (), 'kwargs': {'room_name': '3232'}}}

self.room_group_name = 'chat_%s' % self.room_name
- 直接从用户指定的房间名称构造通道组名称，而无需引号或转义。
- 组名只能包含字母，数字，连字符和句点。因此，此示例代码将在包含其他字符的房间名称上失败。
async_to_sync(self.channel_layer.group_add)(...)
- 加入一个group
- 此方法需要用async_to_sync装饰器, 因为ChatConsumer是一个同步的方法，但是它正在调用异步的layer方法. (所有的layer 方法都是异步的)
self.accept()
- 接收Websocket连接
- 如果未在 connect() 方法中调用 accept() 方法,则连接将被拒绝关闭。例如，你想拒绝一个没有权限的用户连接
async_to_sync(self.channel_layer.group_discard)(...)
- 离开一个group
async_to_sync(self.channel_layer.group_send)
- 将事件发送到group
- 事件具有一个特殊的type 键，改键对应于接收事件使用者中,调用方法的名称

将consumer改写为异步方法

import json
from channels.generic.websocket import AsyncWebsocketConsumer


class ChatConsumer(AsyncWebsocketConsumer):
    async def connect(self):
        self.room_name = self.scope['url_route']['kwargs']['room_name']
        self.room_group_name = 'chat_%s' % self.room_name

        # Join room group
        await self.channel_layer.group_add(
            self.room_group_name,
            self.channel_name
        )

        await self.accept()

    async def disconnect(self, close_code):
        # Leave room group
        await self.channel_layer.group_discard(
            self.room_group_name,
            self.channel_name
        )

    # Receive message from WebSocket
    async def receive(self, text_data):
        text_data_json = json.loads(text_data)
        message = text_data_json['message']

        # Send message to room group
        await self.channel_layer.group_send(
            self.room_group_name,
            {
                'type': 'chat_message',
                'message': message
            }
        )

    # Receive message from room group
    async def chat_message(self, event):
        message = event['message']

        # Send message to WebSocket
        await self.send(text_data=json.dumps({
            'message': message
        }))

原文作者：Momo

原文链接：https://mo.xmomo521.top/2020/09/04/Python-Channels库使用/

发表日期：September 4th 2020, 11:53:37 am

更新日期：December 21st 2021, 3:32:58 pm

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CATALOG

1. 前言
2. 基本设置
3. 实现聊天服务器
1. 3.1. 创建消费者
2. 3.2. 使用 channels layer
4. 将consumer改写为异步方法

