`due_at` date calculation appears to be incorrect about redbeat

[sibson]

good catch, what would you propose to fix?

[simonk52]

In my code I've monkeypatched RedBeatSchedulerEntry with this:

def due_at(self):
    # never run => due now
    if self.last_run_at is None:
        return self._default_now()

    delta = self.schedule.remaining_estimate(self.last_run_at)
    # if no delta, means no more events after the last_run_at.
    if delta is None:
        return None

    # overdue => due now
    if delta.total_seconds() < 0:
        return self._default_now()

    return self.default_now() + delta

ie. just changing the last line to use self.default_now() instead of self.last_run_at. It seems to work, but I confess that I haven't tried running the redbeat tests with that change :-)

[jlaine]

I think I might be getting bitten by this, I run very frequent periodic tasks (i.e. every couple of seconds) and occasionally tasks stop kicking off for exactly 5mn, which looks suspiciously like the default beat_max_loop_interval.

Applying the change suggested by @simonk52 definitely breaks the test suite, specifically tests.test_entry.test_RedBeatEntry.test_due_at.

[ziptnf]

@sibson is there a plan to fix this anytime soon? This seems fairly fixable as per @simonk52 's monkeypatch.