#34747 closed Bug (worksforme)
Django hangs on async views with asycio.gather and an async ORM call
Reported by: | rasca | Owned by: | nobody |
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Component: | Database layer (models, ORM) | Version: | 4.2 |
Severity: | Normal | Keywords: | async asyncio.gather |
Cc: | Triage Stage: | Unreviewed | |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description (last modified by )
This simple view:
import asyncio from django.http import HttpResponse from myapp.models import MyModel async def test_hang(request): await asyncio.gather(MyModel.objects.acreate()) return HttpResponse('OK')
Hangs when called from daphne or uvicorn. When called from the django shell (with ipdb) like await test_hang(None)
it works with no problem.
I created this minimal view to reproduce the issue, but in my project I'm creating a lot of tasks that have long external API requests saving the results to the db. Notice that with only one task it already hangs.
I haven't found anything in the async documentation / channels / daphne stating that I cannot do something like this.
When setting a trace with ipdb I found that the line that gets stuck is:
> /usr/local/Cellar/python@3.11/3.11.4_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/selectors.py:561 kev_list = self._selector.control(None, max_ev, timeout)
And when running with python -m ipdb and then ctrl c it gets stuck in this line:
File "/usr/local/Cellar/python@3.11/3.11.4_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/threading.py", line 1132, in _wait_for_tstate_lock if lock.acquire(block, timeout):
Tried with Python 3.11.4 in OS X and in docker (alpine).
Shouldn't this simple view be working? If not, we should document it somehow. Any pointers much appreciated!
Change History (5)
comment:1 by , 16 months ago
Description: | modified (diff) |
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comment:2 by , 16 months ago
Resolution: | → worksforme |
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Status: | new → closed |
follow-up: 4 comment:3 by , 16 months ago
Thanks a lot Mariusz for taking the time to test the issue and unblocking me!!
I've fixed it. I'm writing my results here for anyone having this problem in the future.
I first created a bare bones project to test that the simple view worked. After that I started removing everything from my project till it started working.
My problem was that I had a middleware not prepared for async and that somehow broke this usage:
My middleware was this one:
from django.http import HttpResponse class HealthCheckMiddleware: def __init__(self, get_response): self.get_response = get_response def __call__(self, request): if request.path == '/health': return HttpResponse('ok') return self.get_response(request)
and I changed it to this one and now it works.
from asgiref.sync import iscoroutinefunction from django.http import HttpResponse from django.utils.decorators import sync_and_async_middleware @sync_and_async_middleware def health_check_middleware(get_response): if iscoroutinefunction(get_response): async def middleware(request): if request.path == '/health': return HttpResponse('ok') response = await get_response(request) return response else: def middleware(request): if request.path == '/health': return HttpResponse('ok') response = get_response(request) return response return middleware
comment:4 by , 16 months ago
Resolution: | worksforme → fixed |
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I was having the same issue, transforming the sync middlewares to async worked for me
Replying to rasca:
Thanks a lot Mariusz for taking the time to test the issue and unblocking me!!
I've fixed it. I'm writing my results here for anyone having this problem in the future.
I first created a bare bones project to test that the simple view worked. After that I started removing everything from my project till it started working.
My problem was that I had a middleware not prepared for async and that somehow broke this usage:
My middleware was this one:
from django.http import HttpResponse class HealthCheckMiddleware: def __init__(self, get_response): self.get_response = get_response def __call__(self, request): if request.path == '/health': return HttpResponse('ok') return self.get_response(request)and I changed it to this one and now it works.
from asgiref.sync import iscoroutinefunction from django.http import HttpResponse from django.utils.decorators import sync_and_async_middleware @sync_and_async_middleware def health_check_middleware(get_response): if iscoroutinefunction(get_response): async def middleware(request): if request.path == '/health': return HttpResponse('ok') response = await get_response(request) return response else: def middleware(request): if request.path == '/health': return HttpResponse('ok') response = get_response(request) return response return middleware
comment:5 by , 16 months ago
Resolution: | fixed → worksforme |
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Yes, and it works for me, with and without
daphne
, this may be some misconfiguration of your server. You can try to useasyncio.TaskGroup()
which is available on Python 3.11+ and check out TicketClosingReasons/UseSupportChannels for ways to get help.