Checking next time to run scheduled periodic jobs in Celery (with Django)

* Using celery 3.1.25 because django-celery-beat 1.0.1 has a problem scheduling periodic tasks.

I recently ran into a celerybeat issue where periodic jobs at intervals of one day or more seem to be "forgotten" by the scheduler. If I change the interval to every 5 seconds

, the task runs fine (every 5 seconds) and the attribute is last_run_at

updated. This means that celerybeat is responsive to the scheduler to a certain extent, but if I reset last_run_at

ie PeriodicTask.objects.update(last_run_at=None)

, none of the interval tasks every day

anymore run.

Celerybeat crashed at some point and it may have damaged something, so I created a new virtualenv and database to see if the problem persists. I would like to know if there is a way to get the next execution time, so that I don't have to wait one day to see if my periodic task has completed.

I also tried using inspect <active/scheduled/reserved>

but everything returned empty

. Is this ok for periodic tasks using the djcelery database scheduler?

Here's a function that schedules tasks:

def schedule_data_collection(request, project):
    if (request.method == 'POST'):
        interval = request.POST.get('interval')

        target_project = Project.objects.get(url_path=project)    
        interval_schedule = dict(every=json.loads(interval), period='days')

        schedule, created = IntervalSchedule.objects.get_or_create(
            every=interval_schedule['every'],
            period=interval_schedule['period'],
        )

        task_name = '{} data collection'.format(target_project.name)

        try:
            task = PeriodicTask.objects.get(name=task_name)
        except PeriodicTask.DoesNotExist:
            task = PeriodicTask.objects.create(
                interval=schedule,
                name=task_name,
                task='myapp.tasks.collect_tool_data',
                args=json.dumps([target_project.url_path])
            )
        else:
            if task.interval != schedule:
                task.interval = schedule

            if task.enabled is False:
                task.enabled = True

            task.save()

        return HttpResponse(task.interval)
    else:
        return HttpResponseForbidden()