When the system time is modified forward, celery beat does not automatically clear “last_run_at” and falls into an endless loop。

[daleeg]

Checklist

• I have verified that the issue exists against the master branch of Celery.
• This has already been asked to the discussion group 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 master branch.
• I have included all related issues and possible duplicate issues
  in this issue (If there are none, check this box anyway).

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 master 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

• 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:

celery report Output:

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

pip freeze Output:

Other Dependencies

N/A

Minimally Reproducible Test Case

Expected Behavior

Actual Behavior

[daleeg]

Solution

from

class ScheduleEntry(object):   
    def is_due(self):
        """See :meth:`~celery.schedule.schedule.is_due`."""
        return self.schedule.is_due(self.last_run_at)

to

class ScheduleEntry(object):   
    def is_due(self):
        """See :meth:`~celery.schedule.schedule.is_due`."""
        current = self.default_now()
        if current < self.last_run_at:
            self.last_run_at = current
        return self.schedule.is_due(self.last_run_at)

[matteius]

@vallee11 Your pip freeze output is empty but this I recall was a bug in an earlier version of Celery 4 that I helped fix. Can you try with the the latest Celery 4.4 and latest Kombu packages?

[daleeg]

The version I used is Celery 4.4, python 3.8. I checked the source code and found no code to handle "self.default_now() < self.last_run_at"

[auvipy]

feel free to contribute as a PR