update_connections_time_zone fails with parallel tests

[Justin Walters]

I have extended the DiscoverRunner to wrap override_settings(USE_TZ=False) around setup_databases and run_suite, in order to allow my tests and migrations to peacefully use timezone-naive test data.

I just began using the manage.py test --parallel to run my tests in parallel. However, even though my tests succeed, the test runner crashes before exiting, with the below exception. My test database does not get torn down as a result. If I remove the override_settings(USE_TZ=False) the exception never occurs.

My guess is that django.test.signals.update_connections_time_zone does not gracefully handle the connection being closed before the function completes. But I think it smells to just silence this exception in this function, and am worried that perhaps my own code somewhere is abusing the db connection. Thoughts?

Traceback (most recent call last):
  File "./manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/commands/test.py", line 26, in run_from_argv
    super().run_from_argv(argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/commands/test.py", line 59, in handle
    failures = test_runner.run_tests(test_labels)
  File "/usr/local/lib/python3.6/site-packages/django/test/runner.py", line 603, in run_tests
    result = self.run_suite(suite)
  File "/code/application/test_runner.py", line 30, in run_suite
    return super(TestRunner, self).run_suite(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/django/test/utils.py", line 343, in __exit__
    self.disable()
  File "/usr/local/lib/python3.6/site-packages/django/test/utils.py", line 419, in disable
    setting=key, value=new_value, enter=False)
  File "/usr/local/lib/python3.6/site-packages/django/dispatch/dispatcher.py", line 178, in send
    for receiver in self._live_receivers(sender)
  File "/usr/local/lib/python3.6/site-packages/django/dispatch/dispatcher.py", line 178, in <listcomp>
    for receiver in self._live_receivers(sender)
  File "/usr/local/lib/python3.6/site-packages/django/test/signals.py", line 74, in update_connections_time_zone
    conn.ensure_timezone()
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/postgresql/base.py", line 193, in ensure_timezone
    cursor.execute(self.ops.set_time_zone_sql(), [timezone_name])
psycopg2.OperationalError: server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.

[Simon Charette]

This should be fixed by 7071f8f2729295b0da77b6c651966dc32c71f1ab (#30193) which is part of the upcoming 3.0 release.

You can confirm it's the case by trying it out against the currently released alpha by installing it from pypi pip install Django==3.0a1.

Please reopen this ticket if it's not the case.

[Justin Walters]

Thanks Simon!