django.db.utils.InterfaceError: connection already closed

[Michele Matera]

Hello!
Stack:

• Ubuntu (20.04 LTS)
• Nginx
• Postgresql (v13.3)

An AWS load balancer sends traffic to the Ubuntu instance(k8s cluster), which is handled by Nginx, which forwards on to Django (4.0.3) running in gunicorn (19.9.0). Django connects to the database using psycopg2 (2.8.6).
The issue I have is that the database connection seems to shut down randomly. Django reports errors like this:

InterfaceError: connection already closed File "django/core/handlers/exception.py", line 55, in inner response = get_response(request) File "django/core/handlers/base.py", line 197, in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) File "contextlib.py", line 79, in inner return func(*args, **kwds) File "django/views/generic/base.py", line 84, in view return self.dispatch(request, *args, **kwargs) File "django/utils/decorators.py", line 46, in _wrapper return bound_method(*args, **kwargs) File "django/views/decorators/cache.py", line 62, in _wrapped_view_func response = view_func(request, *args, **kwargs) File "django/views/generic/base.py", line 119, in dispatch return handler(request, *args, **kwargs) File "django/views/generic/detail.py", line 108, in get self.object = self.get_object() File "django/views/generic/detail.py", line 53, in get_object obj = queryset.get() File "django/db/models/query.py", line 492, in get num = len(clone) File "django/db/models/query.py", line 302, in __len__ self._fetch_all() File "django/db/models/query.py", line 1507, in _fetch_all self._result_cache = list(self._iterable_class(self)) File "django/db/models/query.py", line 57, in __iter__ results = compiler.execute_sql( File "django/db/models/sql/compiler.py", line 1359, in execute_sql cursor = self.connection.cursor() File "django/utils/asyncio.py", line 26, in inner return func(*args, **kwargs) File "django/db/backends/base/base.py", line 284, in cursor return self._cursor() File "django/db/backends/base/base.py", line 262, in _cursor return self._prepare_cursor(self.create_cursor(name)) File "django/db/utils.py", line 91, in __exit__ raise dj_exc_value.with_traceback(traceback) from exc_value File "django/db/backends/base/base.py", line 262, in _cursor return self._prepare_cursor(self.create_cursor(name)) File "django/utils/asyncio.py", line 26, in inner return func(*args, **kwargs) File "django/db/backends/postgresql/base.py", line 256, in create_cursor cursor = self.connection.cursor()

Postgresql does not report any major errors: I can only assume that the connection was closed correctly and Django was not expecting it.
This happens quite rarely, but enough to be a concern: once every 3 days.
Any suggestions of how to investigate this further would be gratefully accepted. Thanks in advance!

[peter.w...@kpn.com]

 

Michele,

 

  > ... the database connection seems to shut down randomly.

 

Could be the same problem as I described in

 

  Database "InterfaceError connection already closed" with asgi.

 

  https://groups.google.com/g/django-users/c/RmtFuCVLfPE/m/dBQjq7FsBQAJ

 

Django doesn't stick to the same thread (sync_to_async with

thread_sensitive=False) when generating a response for exceptions. I

haven't studied Django internals, but it seems that it might be better

to use thread_sensitive=True and try to keep using the database

connection prepared for the current request in the current thread.

 

Regards,

 

Peter Wagemans