ValueError: HTTP response has not yet been started but got http.response.body - web page is freezing on loading.

[HT-Moh]

Hi
I am facing an issue which I am trying to resolve for quite a long time now.
Background
The integration of Daphne with Django and Channels "was working" fine but suddenly stopped working, and I am getting the problem "ValueError: HTTP response has not yet been started but got http.response.body" which I can not resolve. I have ws endpoint which trigger the consumer make celery task calls, I simplified the consumer to the minimum to check if the problem disappear but no luck.
The setup I had it with Django 2 but upgraded to Django 3 to solve the problem but same problem.

channels == 3.0.0
django == 3.1.3
channels-redis == 3.2.0

/static/tradeplatform/styles/scss/dashboard.css' http.response.body
Start writing request
Stop writing request
{'type': 'http.response.body'}
127.0.0.1:33644 - - [04/Nov/2020:12:20:11] "GET /static/tradeplatform/styles/scss/dashboard.css" 304 -
b'/static/jquery/dist/jquery.min.js' http.response.start
b'/static/jquery/dist/jquery.min.js' http.response.body
Start writing request
Stop writing request
{'type': 'http.response.body'}
127.0.0.1:33644 - - [04/Nov/2020:12:20:11] "GET /static/jquery/dist/jquery.min.js" 304 -
2020-11-04 12:20:12,537 ERROR    Exception inside application: HTTP response has not yet been started but got http.response.body
Traceback (most recent call last):
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/channels/routing.py", line 71, in __call__
    return await application(scope, receive, send)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/channels/http.py", line 200, in __call__
    await self.handle(body_stream)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/asgiref/sync.py", line 304, in __call__
    ret = await asyncio.wait_for(future, timeout=None)
  File "/usr/lib/python3.8/asyncio/tasks.py", line 455, in wait_for
    return await fut
  File "/usr/lib/python3.8/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/asgiref/sync.py", line 343, in thread_handler
    return func(*args, **kwargs)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/channels/http.py", line 258, in handle
    self.send(response_message)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/asgiref/sync.py", line 147, in __call__
    return call_result.result()
  File "/usr/lib/python3.8/concurrent/futures/_base.py", line 432, in result
    return self.__get_result()
  File "/usr/lib/python3.8/concurrent/futures/_base.py", line 388, in __get_result
    raise self._exception
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/asgiref/sync.py", line 212, in main_wrap
    result = await self.awaitable(*args, **kwargs)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/daphne/server.py", line 233, in handle_reply
    protocol.handle_reply(message)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/daphne/http_protocol.py", line 262, in handle_reply
    raise ValueError(
ValueError: HTTP response has not yet been started but got http.response.body
b'/static/bootstrap4/dist/css/bootstrap.min.css' http.response.start
2020-11-04 12:20:12,540 ERROR    Exception in callback AsyncioSelectorReactor.callLater.<locals>.run() at /home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/twisted/internet/asyncioreactor.py:287
handle: <TimerHandle when=67852.310794924 AsyncioSelectorReactor.callLater.<locals>.run() at /home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/twisted/internet/asyncioreactor.py:287>
Traceback (most recent call last):
  File "/usr/lib/python3.8/asyncio/events.py", line 81, in _run
    self._context.run(self._callback, *self._args)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/twisted/internet/asyncioreactor.py", line 290, in run
    f(*args, **kwargs)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/daphne/server.py", line 295, in application_checker
    protocol.handle_exception(exception)
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/daphne/http_protocol.py", line 307, in handle_exception
    self.basic_error(500, b"Internal Server Error", "Exception inside application.")
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/daphne/http_protocol.py", line 348, in basic_error
    self.handle_reply(
  File "/home/moh/codess/trade-platoform/.venv/lib/python3.8/site-packages/daphne/http_protocol.py", line 244, in handle_reply
    raise ValueError("HTTP response has already been started")
ValueError: HTTP response has already been started
b'/media/img/components_images/WTP%20Product%20Images/TagFa
 

The code

# wsgi
import os
from django.core.wsgi import get_wsgi_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "myapp.settings")
application = get_wsgi_application()

# asgi.py
import os
import django
from myapp.wsgi import *
from channels.routing import get_default_application

from channels.sessions import SessionMiddlewareStack
from tp_celery.consumers import UpdateOrderStatus
from channels.routing import ProtocolTypeRouter, URLRouter
from django.urls import path
from myapp.routing import websocket_urlpatterns

application = ProtocolTypeRouter({

    "websocket": SessionMiddlewareStack(
        URLRouter(websocket_urlpatterns)
    ),

})

# 
rooting.py
from tp_celery.consumers import UpdateOrderStatus
from django.urls import path

websocket_urlpatterns = [
    path("ws/update-order-status/", UpdateOrderStatus),
]

# consummer.py
from channels.consumer import SyncConsumer

class UpdateOrderStatus(SyncConsumer):

    def websocket_connect(self, event):
        self.send({
            "type": "websocket.accept",
        })

    def websocket_receive(self, event):
        self.send({
            "type": "websocket.send",
            "text": event["text"],
        })

What I notice as well by simplifying the page template if I delete the row where we use the static `link href="{% static 'awesome-bootstrap-checkbox/awesome-bootstrap-checkbox.css' %}" rel="stylesheet" />
the page is loading and it's not blocked, and If I add a any source using static it does freeze.

{% load i18n  sekizai_tags static sass_tags %}

<!doctype html>
<html lang="en">
<head>
    <title>Tradeplatform</title>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="description" content="{% block tp_desc %}Tradeplatform description{% endblock %}">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.14.0/css/all.css">
    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.14.0/css/v4-shims.css">
    <link href="{% static 'bootstrap4/dist/css/bootstrap.min.css' %}" rel="stylesheet" />
    <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet">
    <link href="https://fonts.googleapis.com/css?family=Ubuntu" rel="stylesheet">

    <!-- <link href="{% static 'bootstrap-datepicker/dist/css/bootstrap-datepicker.min.css' %}" rel="stylesheet" /> -->
    <link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/daterangepicker/daterangepicker.css" />

    <link href="{% static 'awesome-bootstrap-checkbox/awesome-bootstrap-checkbox.css' %}" rel="stylesheet" />

</head>

</body>

</html>
``

[arthtyagi]

Yeah, I'm facing the same issue. That too out of the blue, what do I even do in such a situation?

[carltongibson]

Upgrade to Channels 3.0.1, and make sure to review the 3.0.0 release notes — it's a major version upgrade.

At the least it looks like you'll need to as as_asgi() calls when routing your consumers.

[arthtyagi]

That doesn't work. Also looked at the docs and changed my code as indicated.

asgi.py

"""
import os
import django

# from django.core.asgi import get_asgi_application

from channels.routing import get_default_application

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'domecode.devsettings')
django.setup()  # to deploy with asgi when using channels
application = get_default_application()
"""
change devsettings to settings when deploying
"""

routing.py - project level

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

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

routing.py - application level ( messaging )

from messaging import consumers
from django.urls import re_path

websocket_urlpatterns = [
    re_path(r'^wss$', consumers.ChatConsumer.as_asgi()),
    # change to ws during testing
]