Django Channels聊天项目报错：'set' object has no attribute 'decode'

问题场景 #

开发学校Django聊天项目，使用WebSocket（Django Channels + Daphne），重载应用时触发AttributeError: 'set' object has no attribute 'decode'，未手动调用decode()方法。

相关代码 #

consumers.py #

from channels.generic.websocket import WebsocketConsumer

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

    def disconnect(self, code):
        pass

routing.py #

from django.urls import path
from . import consumers

websocket_urlpatterns = [
  # path('chat/', consumers.ChatConsumer.as_asgi())
  path('chat/', consumers.ChatConsumer.as_asgi())
]

asgi.py #

import chat.routing
import os

from channels.routing import ProtocolTypeRouter, URLRouter
from channels.security.websocket import AllowedHostsOriginValidator
from django_channels_jwt_auth_middleware.auth import JWTAuthMiddlewareStack
from django.core.asgi import get_asgi_application

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

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

错误回溯 #

WebSocket HANDSHAKING /chat/ [127.0.0.1:49878]
WebSocket CONNECT /chat/ [127.0.0.1:49878]
Exception inside application: 'set' object has no attribute 'decode'
Traceback (most recent call last):
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/django/contrib/staticfiles/handlers.py", line 101, in __call__
    return await self.application(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/routing.py", line 62, in __call__
    return await application(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/security/websocket.py", line 37, in __call__
    return await self.application(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/django_channels_jwt_auth_middleware/auth.py", line 36, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/sessions.py", line 47, in __call__
    return await self.inner(dict(scope, cookies=cookies), receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/sessions.py", line 263, in __call__
    return await self.inner(wrapper.scope, receive, wrapper.send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/auth.py", line 185, in __call__
    return await super().__call__(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/middleware.py", line 24, in __call__
    return await self.inner(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/routing.py", line 116, in __call__
    return await application(
           ^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/consumer.py", line 94, in app
    return await consumer(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/consumer.py", line 58, in __call__
    await await_many_dispatch(
  File "/Users/macbook/programacao/pap/env/lib/python3.12/site-packages/channels/utils.py", line 57, in await_many_dispatch
    await task
AttributeError: 'set' object has no attribute 'decode'
WebSocket DISCONNECT /chat/ [127.0.0.1:49878]

解决方案 #

从错误栈可定位问题出在django_channels_jwt_auth_middleware中间件，结合Python 3.12版本，大概率是中间件版本不兼容或内部逻辑错误将值转为集合（set）而非字符串，导致decode()调用失败。

具体解决步骤： #

1. 临时移除JWT中间件验证
   注释asgi.py中的JWTAuthMiddlewareStack，直接使用URLRouter，验证错误是否消失：

   application = ProtocolTypeRouter({
       'http': get_asgi_application(),
       'websocket': AllowedHostsOriginValidator(
           # JWTAuthMiddlewareStack(
               URLRouter(chat.routing.websocket_urlpatterns)
           # )
       )
   })
   

   若错误消失，确认问题来自该JWT中间件。

2. 更新或更换JWT中间件

   • 执行命令更新中间件，查看是否有Python 3.12兼容版本：

     pip install --upgrade django_channels_jwt_auth_middleware
     

   • 若无兼容更新，改用维护更活跃的Channels JWT中间件（如channels-jwt-auth），或自行实现简易JWT验证逻辑。

3. 检查JWT配置
   确认Django settings中JWT相关配置（如SECRET_KEY、JWT_AUTH参数）是否正确，避免将配置项错误设为集合类型（如用{}替代""）。

4. 降级Python版本（备选）
   若暂时无兼容中间件，可将Python降级至3.11或更早版本，提升与旧中间件的兼容性。

内容的提问来源于stack exchange，提问作者user23970573