I’ve been attempting to upgrade python from 3.6 to 3.7 for our Django & Django channels application. With that change, Django throws a SynchronousOnlyOperation
anytime any HTTP request is made (even if it has nothing to do with WebSockets). My guess is that somehow the python upgrade has made the Django check more strict.
I believe that Django channels are serving both the HTTP requests and WebSocket requests so it expects all code to be async compliant.
How do I get Django channels runserver
to run the wsgi
app synchronously, while the channel consumers asynchronously?
# project/asgi.py
application = ProtocolTypeRouter({"http": get_asgi_application(), "websocket": routing})
# project/wsgi.py
application = get_wsgi_application()
Stacktrace:
It’s clear to me that the auth middleware that is running for a normal wsgi view is not async compliant, how can I get it to run in a sync environment?
ERROR Internal Server Error: /a/api
Traceback (most recent call last):
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/sessions/backends/base.py", line 233, in _get_session
return self._session_cache
AttributeError: 'SessionStore' object has no attribute '_session_cache'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/core/handlers/exception.py", line 47, in inner
response = get_response(request)
File "/___/___/___/___/apps/core/middleware.py", line 60, in __call__
request.is_user_verified = request.user.is_verified()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/utils/functional.py", line 240, in inner
self._setup()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/utils/functional.py", line 376, in _setup
self._wrapped = self._setupfunc()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django_otp/middleware.py", line 38, in _verify_user
user.otp_device = None
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/utils/functional.py", line 270, in __setattr__
self._setup()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/utils/functional.py", line 376, in _setup
self._wrapped = self._setupfunc()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/auth/middleware.py", line 24, in <lambda>
request.user = SimpleLazyObject(lambda: get_user(request))
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/auth/middleware.py", line 12, in get_user
request._cached_user = auth.get_user(request)
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/auth/__init__.py", line 174, in get_user
user_id = _get_user_session_key(request)
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/auth/__init__.py", line 58, in _get_user_session_key
return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/sessions/backends/base.py", line 65, in __getitem__
return self._session[key]
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/sessions/backends/base.py", line 238, in _get_session
self._session_cache = self.load()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/sessions/backends/db.py", line 43, in load
s = self._get_session_from_db()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/contrib/sessions/backends/db.py", line 34, in _get_session_from_db
expire_date__gt=timezone.now()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/db/models/manager.py", line 85, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/db/models/query.py", line 425, in get
num = len(clone)
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/db/models/query.py", line 269, in __len__
self._fetch_all()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/db/models/query.py", line 1303, in _fetch_all
self._result_cache = list(self._iterable_class(self))
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/db/models/query.py", line 53, in __iter__
results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/db/models/sql/compiler.py", line 1154, in execute_sql
cursor = self.connection.cursor()
File "/___/___/.pyenv/versions/pd37/lib/python3.7/site-packages/django/utils/asyncio.py", line 24, in inner
raise SynchronousOnlyOperation(message)
django.core.exceptions.SynchronousOnlyOperation: You cannot call this from an async context - use a thread or sync_to_async.
Versions
Django==3.1.1
channels==3.0.2
channels-redis==3.2.0
2
Answers
Finally got to the bottom of this. For us, we were using
gevent
and had this line in our manage.pyFor whatever reason, that does not play nicely with python 3.7+, Django channels, and Django (where python 3.6, Django channels, and Django worked fine).
We were lucky and were able to remove this from our codebase; we did not figure out how to fix the
gevent
patch.So a summary of what I’ve tried:
I can pull up DRF’s standard views, create entries etc.
Then added a simple middleware that accesses the database (gets a count of the number of Agencies and puts it in request). Not even using MiddlewareMixin, just barebones init can call protocol.
The stack uses local nginx to route to port 3401 for
/ws
(websocket) and/agencies
(http). Perhaps you spot something…