WorkerThread server closed the connection unexpectedly

[blessing-gao]

When redis connection is used, redis and the server are connected through docker network on the same machine, the following problem often occurs. When reading the error, the db cannot be connected, but redis is running normally

[dramatiq.worker.WorkerThread:409]  - Failed to process message judge_task('5278736edc1ded50085a726a50a8d0ef', 1160) with unhandled exception.
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
psycopg2.OperationalError: server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/dramatiq/worker.py", line 397, in process_message
    res = actor(*message.args, **message.kwargs)
  File "/usr/local/lib/python3.7/site-packages/dramatiq/actor.py", line 213, in __call__
    return self.fn(*args, **kwargs)
  File "./judge/tasks.py", line 11, in judge_task
    uid = Submission.objects.get(id=submission_id).user_id
  File "/usr/local/lib/python3.7/site-packages/django/db/models/manager.py", line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/db/models/query.py", line 393, in get
    num = len(clone)
  File "/usr/local/lib/python3.7/site-packages/django/db/models/query.py", line 250, in __len__
    self._fetch_all()
  File "/usr/local/lib/python3.7/site-packages/django/db/models/query.py", line 1186, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/usr/local/lib/python3.7/site-packages/django/db/models/query.py", line 54, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "/usr/local/lib/python3.7/site-packages/django/db/models/sql/compiler.py", line 1065, in execute_sql
    cursor.execute(sql, params)
  File "/usr/local/lib/python3.7/site-packages/raven/contrib/django/client.py", line 127, in execute
    return real_execute(self, sql, params)
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 68, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python3.7/site-packages/django/db/utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
django.db.utils.OperationalError: server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.