Sometimes celery beat crashes with the following error: UnpicklingError - invalid load key.

I will work on a fix soon.

Here is the relevant stack trace:

Traceback (most recent call last):
  File "shelve.py", line 111, in __getitem__
    value = self.cache[key]
KeyError: 'entries'
Traceback (most recent call last):
  File "celery/apps/beat.py", line 105, in start_scheduler
    service.start()
  File "celery/beat.py", line 636, in start
    humanize_seconds(self.scheduler.max_interval))
  File "kombu/utils/objects.py", line 30, in __get__
    return super().__get__(instance, owner)
  File "functools.py", line 993, in __get__
    val = self.func(instance)
  File "celery/beat.py", line 680, in scheduler
    return self.get_scheduler()
  File "celery/beat.py", line 671, in get_scheduler
    return symbol_by_name(self.scheduler_cls, aliases=aliases)(
  File "celery/beat.py", line 515, in __init__
    super().__init__(*args, **kwargs)
  File "celery/beat.py", line 271, in __init__
    self.setup_schedule()
  File "celery/beat.py", line 543, in setup_schedule
    self._create_schedule()
  File "celery/beat.py", line 572, in _create_schedule
    self._store['entries']
  File "shelve.py", line 114, in __getitem__
    value = Unpickler(f).load()
UnpicklingError: invalid load key, '\xf2'.

Checklist

• I have verified that the issue exists against the main branch of Celery.
• This has already been asked to the discussions forum first.
• I have read the relevant section in the
  contribution guide
  on reporting bugs.
• I have checked the issues list
  for similar or identical bug reports.
• I have checked the pull requests list
  for existing proposed fixes.
• I have checked the commit log
  to find out if the bug was already fixed in the main branch.
• I have included all related issues and possible duplicate issues
  in this issue (If there are none, check this box anyway).
• I have tried to reproduce the issue with pytest-celery and added the reproduction script below.

Mandatory Debugging Information

• I have included the output of celery -A proj report in the issue.
  (if you are not able to do this, then at least specify the Celery
  version affected).
• I have verified that the issue exists against the main branch of Celery.
• I have included the contents of pip freeze in the issue.
• I have included all the versions of all the external dependencies required
  to reproduce this bug.

Optional Debugging Information

Here is the relevant stack trace:

Traceback (most recent call last):
  File "shelve.py", line 111, in __getitem__
    value = self.cache[key]
KeyError: 'entries'
Traceback (most recent call last):
  File "celery/apps/beat.py", line 105, in start_scheduler
    service.start()
  File "celery/beat.py", line 636, in start
    humanize_seconds(self.scheduler.max_interval))
  File "kombu/utils/objects.py", line 30, in __get__
    return super().__get__(instance, owner)
  File "functools.py", line 993, in __get__
    val = self.func(instance)
  File "celery/beat.py", line 680, in scheduler
    return self.get_scheduler()
  File "celery/beat.py", line 671, in get_scheduler
    return symbol_by_name(self.scheduler_cls, aliases=aliases)(
  File "celery/beat.py", line 515, in __init__
    super().__init__(*args, **kwargs)
  File "celery/beat.py", line 271, in __init__
    self.setup_schedule()
  File "celery/beat.py", line 543, in setup_schedule
    self._create_schedule()
  File "celery/beat.py", line 572, in _create_schedule
    self._store['entries']
  File "shelve.py", line 114, in __getitem__
    value = Unpickler(f).load()
UnpicklingError: invalid load key, '\xf2'.

• I have tried reproducing the issue on more than one Python version
  and/or implementation.
• I have tried reproducing the issue on more than one message broker and/or
  result backend.
• I have tried reproducing the issue on more than one version of the message
  broker and/or result backend.
• I have tried reproducing the issue on more than one operating system.
• I have tried reproducing the issue on more than one workers pool.
• I have tried reproducing the issue with autoscaling, retries,
  ETA/Countdown & rate limits disabled.
• I have tried reproducing the issue after downgrading
  and/or upgrading Celery and its dependencies.

Related Issues and Possible Duplicates

Related Issues

• None

Possible Duplicates

• None

Environment & Settings

Celery version:

Steps to Reproduce

Required Dependencies

• Minimal Python Version: N/A or Unknown
• Minimal Celery Version: N/A or Unknown
• Minimal Kombu Version: N/A or Unknown
• Minimal Broker Version: N/A or Unknown
• Minimal Result Backend Version: N/A or Unknown
• Minimal OS and/or Kernel Version: N/A or Unknown
• Minimal Broker Client Version: N/A or Unknown
• Minimal Result Backend Client Version: N/A or Unknown

Python Packages

Other Dependencies

Minimally Reproducible Test Case

Expected Behavior

Actual Behavior