Checking the next run time for scheduled periodic tasks in Celery (with Django)

Question

*Using celery 3.1.25 because django-celery-beat 1.0.1 has an issue with scheduling periodic tasks.

Recently I encountered an issue with celerybeat whereby periodic tasks with an interval of a day or longer appear to be 'forgotten' by the scheduler. If I change the interval to every 5 seconds the task executes normally (every 5 seconds) and the last_run_at attribute gets updated. This means celerybeat is responding to the scheduler to a certain degree, but if I reset the last_run_at i.e. PeriodicTask.objects.update(last_run_at=None), none of the tasks with an interval of every day run anymore.

Celerybeat crashed at one point and that may have corrupted something so I created a new virtualenv and database to see if the problem persists. I'd like to know if there is a way to retrieve the next run time so that I don't have to wait a day to know whether or not my periodic task has been executed.

I have also tried using inspect <active/scheduled/reserved> but all returned empty. Is this normal for periodic tasks using djcelery's database scheduler?

Here's the function that schedules the 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()

Strait

What're using for your backend? It should registered in the database. – Attlee

@sdolan I am using RabbitMQ w/PostgreSQL. The scheduler updates itself whenever I add a new instance of the task but still does not trigger the worker to execute it. – Strait

Answer 1

You can see your scheduler by going into shell and looking at app.conf.CELERYBEAT_SCEDULE.

celery -A myApp shell
print(app.conf.CELERYBEAT_SCHEDULE)

This should show you all your Periodic Tasks.

Niu