Celery: Tens of thousands of backend_cleanup tasks executed every night since 10:42 pm. All async functions stop working

I just found that the problem is probably about the built-in task, celery.backend_cleanup. I just ran the app in the local development environment. When it was 10:42 pm, tremendous backend_cleanup tasks started and executed successfully. However, after a couple of seconds, an error occurred. Here is the error.

[2017-10-23 22:51:27,677: CRITICAL/MainProcess] Unrecoverable error: Exception('Request Empty body  HTTP 599  Server aborted the SSL handshake (None)',)
Traceback (most recent call last):
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/celery/worker/worker.py", line 203, in start
    self.blueprint.start(self)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/celery/bootsteps.py", line 119, in start
    step.start(parent)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/celery/bootsteps.py", line 370, in start
    return self.obj.start()
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/celery/worker/consumer/consumer.py", line 320, in start
    blueprint.start(self)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/celery/bootsteps.py", line 119, in start
    step.start(parent)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/celery/worker/consumer/consumer.py", line 596, in start
    c.loop(*c.loop_args())
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/celery/worker/loops.py", line 88, in asynloop
    next(loop)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/kombu/async/hub.py", line 354, in create_loop
    cb(*cbargs)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/kombu/async/http/curl.py", line 111, in on_readable
    return self._on_event(fd, _pycurl.CSELECT_IN)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/kombu/async/http/curl.py", line 124, in _on_event
    self._process_pending_requests()
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/kombu/async/http/curl.py", line 132, in _process_pending_requests
    self._process(curl, errno, reason)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/kombu/async/http/curl.py", line 178, in _process
    buffer=buffer, effective_url=effective_url, error=error,
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/promises.py", line 150, in __call__
    svpending(*ca, **ck)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/promises.py", line 143, in __call__
    return self.throw()
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/promises.py", line 140, in __call__
    retval = fun(*final_args, **final_kwargs)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/funtools.py", line 100, in _transback
    return callback(ret)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/promises.py", line 143, in __call__
    return self.throw()
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/promises.py", line 140, in __call__
    retval = fun(*final_args, **final_kwargs)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/funtools.py", line 98, in _transback
    callback.throw()
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/vine/funtools.py", line 96, in _transback
    ret = filter_(*args + (ret,), **kwargs)
  File "/Users/user/code/accusize-021/lib/python3.4/site-packages/kombu/async/aws/connection.py", line 253, in _on_status_ready
    raise self._for_status(response, response.read())
Exception: Request Empty body  HTTP 599  Server aborted the SSL handshake (None)

Meanwhile, the queue disappeared from AWS SQS. Then a few of the backend_cleanup tasks continued to execute. And finally, a warning showed up.

[2017-10-23 22:51:28,967: WARNING/MainProcess] Restoring 10 unacknowledged message(s)

And finally, the HTTPS connection to the SQS queue stopped. The app could not re-connect to SQS unless I re-deployed the app to AWS Elastic Beanstalk.

Could anyone help me with this issue? Any response will be significantly appreciated.

I think I solved the issue. The problem never happens after I changed CELERY_RESULT_BACKEND to "redis" from "django-db", and change CELERY_TIMEZONE to "UTC". Although the Task Results in Django Admin stopped adding any task results, my problem had been majorly solved.

You can simply overwrite the schedule and avoid using crontab:
'celery.backend_cleanup': { 'task': 'celery.backend_cleanup', 'schedule': 86400, # every 24 hours instead of crontab('0', '4', '*') which is used in celery beat 'options': {'expires': 12 * 3600}} ,