Celery beat is not showing or executing scheduled tasks - python-3.x

Question

I am using celery and celery beat to handle task execution and scheduled tasks in a Python project. I am not using django.
Execution of celery tasks is working as expected. However I have run into a wall trying to get scheduled tasks (celery beat) to run.
I have followed the celery documentation to add my task to app.conf.beat_schedule successfully. If I print out the beat schedule after adding my task, I can see that the task has been added to app.conf.beat_schedule successfully.
from celery import Celery
from celery.task import task
# Celery init
app = Celery('tasks', broker='pyamqp://guest#localhost//')
# get the latest device reading from the appropriate provider
#app.task(bind=True, retry_backoff=True)
def get_reading(self, provider, path, device, config, location, callback):
logger.info("get_reading() called")
module = importlib.import_module('modules.%s' % provider)
try:
module.get_reading(path, device, config, location, callback)
except Exception as e:
self.retry(exc=e)
# add the periodic task
def add_get_reading_periodic_task(provider, path, device, config, location, callback, interval = 600.0):
app.conf.beat_schedule = {
"poll-provider": {
"task": "get_reading",
"schedule": interval,
"args": (provider, path, device, config, location, callback)
}
}
logger.info(app.conf.beat_schedule)
logger.info("Added task 'poll-provider' for %s to beat schedule" % provider)
Looking at my application log, I can see that app.conf.beat_schedule has been updated with the data passed to add_get_reading_periodic_task():
2017-08-17 11:07:13,216 - gateway - INFO - {'poll-provider': {'task': 'get_reading', 'schedule': 10, 'args': ('provider1', '/opt/provider1', None, {'location': {'lan.local': {'uri': 'http://192.168.1.10'}}}, 'lan.local', {'url': 'http://localhost:8080', 'token': '*******'})}}
2017-08-17 11:07:13,216 - gateway - INFO - Added task 'poll-provider' for provider1 to beat schedule
I'm manually running celery worker and celery beat simultaneously (in different terminal windows) on the same application file:
$ celery worker -A gateway --loglevel=INFO
$ celery beat -A gateway --loglevel=DEBUG
If I call get_reading.delay(...) within my application, it is executed by the celery worker as expected.
However, the celery beat process never shows any indication that the scheduled task is registered:
celery beat v4.0.2 (latentcall) is starting.
__ - ... __ - _
LocalTime -> 2017-08-17 11:05:15
Configuration ->
. broker -> amqp://guest:**#localhost:5672//
. loader -> celery.loaders.app.AppLoader
. scheduler -> celery.beat.PersistentScheduler
. db -> celerybeat-schedule
. logfile -> [stderr]#%DEBUG
. maxinterval -> 5.00 minutes (300s)
[2017-08-17 11:05:15,228: DEBUG/MainProcess] Setting default socket timeout to 30
[2017-08-17 11:05:15,228: INFO/MainProcess] beat: Starting...
[2017-08-17 11:05:15,248: DEBUG/MainProcess] Current schedule:
<ScheduleEntry: celery.backend_cleanup celery.backend_cleanup() <crontab: 0 4 * * * (m/h/d/dM/MY)>
[2017-08-17 11:05:15,248: DEBUG/MainProcess] beat: Ticking with max interval->5.00 minutes
[2017-08-17 11:05:15,250: DEBUG/MainProcess] beat: Waking up in 5.00 minutes.
[2017-08-17 11:10:15,351: DEBUG/MainProcess] beat: Synchronizing schedule...
[2017-08-17 11:10:15,355: DEBUG/MainProcess] beat: Waking up in 5.00 minutes.
[2017-08-17 11:15:15,400: DEBUG/MainProcess] beat: Synchronizing schedule...
[2017-08-17 11:15:15,402: DEBUG/MainProcess] beat: Waking up in 5.00 minutes.
[2017-08-17 11:20:15,502: DEBUG/MainProcess] beat: Synchronizing schedule...
[2017-08-17 11:20:15,504: DEBUG/MainProcess] beat: Waking up in 5.00 minutes.
This is seemingly confirmed by running celery inspect scheduled:
-> celery#localhost.lan: OK
- empty -
I have tried starting celery beat both before and after adding the scheduled task to app.conf.beat_schedule, and in both cases the scheduled task never appears in celery beat.
I read that celery beat did not support dynamic reloading of the configuration until version 4, but I am running celery beat 4.0.2
What am I doing wrong here? Why isn't celery beat showing my scheduled task?

Answer 1

Have you tried using the code as described in the Documentation:
#app.on_after_configure.connect
def setup_periodic_tasks(sender, **kwargs):
# Calls test('hello') every 10 seconds.
sender.add_periodic_task(10.0, test.s('hello'), name='add every 10')
?

Answer 2

create a model for creating periodic tasks:
class TaskScheduler(models.Model):
periodic_task = models.OneToOneField(
PeriodicTask, on_delete=models.CASCADE, blank=True, null=True)
node = models.OneToOneField(
Node, on_delete=models.CASCADE, blank=True, null=True)
#staticmethod
def schedule_every(task_name, period, every, sheduler_name, args, queue=None):
# schedules a task by name every "every" "period". So an example call would be:
# TaskScheduler('mycustomtask', 'seconds', 30, [1,2,3])
# that would schedule your custom task to run every 30 seconds with the arguments 1,2 and 3 passed to the actual task.
permissible_periods = ['days', 'hours', 'minutes', 'seconds']
if period not in permissible_periods:
raise Exception('Invalid period specified')
# create the periodic task and the interval
# create some name for the period task
ptask_name = sheduler_name
interval_schedules = IntervalSchedule.objects.filter(
period=period, every=every)
if interval_schedules: # just check if interval schedules exist like that already and reuse em
interval_schedule = interval_schedules[0]
else: # create a brand new interval schedule
interval_schedule = IntervalSchedule()
interval_schedule.every = every # should check to make sure this is a positive int
interval_schedule.period = period
interval_schedule.save()
if(queue):
ptask = PeriodicTask(name=ptask_name, task=task_name,
interval=interval_schedule, queue=queue)
else:
ptask = PeriodicTask(name=ptask_name, task=task_name,
interval=interval_schedule)
if(args):
ptask.args = args
ptask.save()
return TaskScheduler.objects.create(periodic_task=ptask)
#staticmethod
def schedule_cron(task_name, at, sheduler_name, args):
# schedules a task by name every day at the #at time.
# create some name for the period task
ptask_name = sheduler_name
crons = CrontabSchedule.objects.filter(
hour=at.hour, minute=at.minute)
if crons: # just check if CrontabSchedule exist like that already and reuse em
cron = crons[0]
else: # create a brand new CrontabSchedule
cron = CrontabSchedule()
cron.hour = at.hour
cron.minute = at.minute
cron.save()
ptask = PeriodicTask(name=ptask_name,
crontab=cron, task=task_name)
if(args):
ptask.args = args
ptask.save()
return TaskScheduler.objects.create(periodic_task=ptask)
def stop(self):
""" pauses the task """
ptask = self.periodic_task
ptask.enabled = False
ptask.save()
def start(self):
ptask = self.periodic_task
ptask.enabled = True
ptask.save()
def terminate(self):
self.stop()
ptask = self.periodic_task
PeriodicTask.objects.get(name=ptask.name).delete()
self.delete()
ptask.delete()
and then from you code
# give the periodic task a unique name
scheduler_name = "%s_%s" % ('node_heartbeat', str(node.pk))
# organize the task arguments
args = json.dumps([node.extern_id, node.pk])
# create the periodic task in heartbeat queue
task_scheduler = TaskScheduler().schedule_every(
'core.tasks.pdb_heartbeat', 'seconds', 15, scheduler_name , args, 'heartbeat')
task_scheduler.node = node
task_scheduler.save()
the original class I came across here a long time ago I've added schedule_cron