scheduler wont lauch tasks if DatabaseScheduler: Schedule changed.

[celery]

scheduler wont lauch tasks if DatabaseScheduler: Schedule changed.

[fatruchir0]

@auvipy - this is still happening on django-celery-beat==2.2.1 - could you please help me with if this would be fixed? or if there's a workaround?

[marco-silva0000]

I was thinking what would be the best way to fix this and im happy to submit a PR if I can find anything

In my speciefic case, the problem is worse because the lunched task will save the Model instance and always prompt a new rescheduling of tasks, so if 2 or 3 are bound to run, and the first one finishes before the scheduler lunches everything, the problem will happen

[rh0dium]

Hi there,

I can confirm this is a problem.
The simplest way to reproduce this is to create a task like so

@periodic_task(run_every=datetime.timedelta(minutes=2), options={"expires": 90})
def periodic_test(**kwargs):
    print("Running Task")

Then restart both services

celery -A celery_app worker --events -B -S django -l debug
celery -A celery_app events -l debug --camera django_celery_monitor.camera.Camera --frequency=2

Finally go into the periodic tasks in django admin and change a value or disable any other periodic task. As reported in in another issue the schedule doesn't change even though it is committed to the db.

If you then stop and restart the services and it will no longer schedule anything. To rectify the situation I found I can delete all periodic tasks and restart both the celery worker and camera and viola everything is back to normal.

FYI:

celery -A celery_app report

software -> celery:4.0.2 (latentcall) kombu:4.0.2 py:2.7.10
            billiard:3.5.0.2 py-amqp:2.1.4
platform -> system:Darwin arch:64bit imp:CPython
loader   -> celery.loaders.app.AppLoader
settings -> transport:amqp results:django-db

CELERY_BROKER_PORT: u'5672'
CELERY_RESULT_SERIALIZER: u'json'
CELERY_BROKER_URL: u'amqp://icmadmin:********@localhost:5672/icmanage'
CELERY_TASK_TIME_LIMIT: 28800
CELERY_TASK_TRACK_STARTED: True
CELERY_WORKER_CONCURRENCY: 4
CELERY_BROKER_HOST: u'localhost'
CELERY_BROKER_USER: u'icmadmin'
CELERY_RESULT_BACKEND: u'django-db'
CELERY_TASK_SERIALIZER: u'json'
CELERY_BROKER_PASSWORD: u'********'
CELERY_ACCEPT_CONTENT: [u'json']
CELERY_BEAT_SCHEDULER: u'django_celery_beat.schedulers:DatabaseScheduler'
CELERY_SEND_EVENTS: True
CELERY_SEND_TASK_ERROR_EMAILS: True