There is a specific periodic task that needs to be removed from message queue. I am using the configuration of Redis and celery here.
tasks.py
#periodic_task(run_every=crontab(minute='*/6'))
def task_abcd():
"""
some operations here
"""
There are other periodic tasks also in the project but I need to stop this specific task to stop from now on.
As explained in this answer, the following code will work?
#periodic_task(run_every=crontab(minute='*/6'))
def task_abcd():
pass
In this example periodic task schedule is defined directly in code, meaning it is hard-coded and cannot be altered dynamically without code change and app re-deploy.
The provided code with task logic deleted or with simple return at the beginning - will work, but will not be the answer to the question - task will still run, there just is no code that will run with it.
Also, it is recommended NOT to use #periodic_task:
"""Deprecated decorator, please use :setting:beat_schedule."""
so it is not recommended to use it.
First, change method from being #periodic_task to just regular celery #task, and because you are using Django - it is better to go straightforward for #shared_task:
from celery import shared_task
#shared_task
def task_abcd():
...
Now this is just one of celery tasks, which needs to be called explicitly. Or it can be run periodically if added to celery beat schedule.
For production and if using multiple workers it is not recommended to run celery worker with embedded beat (-B) - run separate instance of celery beat scheduler.
Schedule can specified in celery.py or in django project settings (settings.py).
It is still not very dynamic, as to re-read settings app needs to be reloaded.
Then, use Database Scheduler which will allow dynamically creating schedules - which tasks need to be run and when and with what arguments. It even provides nice django admin web views for administration!
That code will work but I'd go for something that doesn't force you to update your code every time you need to disable/enable the task.
What you could do is to use a configurable variable whose value could come from an admin panel, a configuration file, or whatever you want, and use that to return before your code runs if the task is in disabled mode.
For instance:
#periodic_task(run_every=crontab(minute='*/6'))
def task_abcd():
config = load_config_for_task_abcd()
if not config.is_enabled:
return
# some operations here
In this way, even if your task is scheduled, its operations won't be executed.
If you simply want to remove the periodic task, have you tried to remove the function and then restart your celery service. You can restart your Redis service as well as your Django server for safe measure.
Make sure that the function you removed is not referenced anywhere else.
Related
I am trying to find a way to add a new task to celery after celery worker has been executed and after celery has been instantiated. I basically want to add a new task with a dynamic name based on user input. I will also want to set a rate limit for that new task.
I have not been able to find any documentation on this and no examples on my google searches. All I have been able to find is dynamically adding periodic tasks with celery beat.
Is there any way to do what I am looking to do?
What you want to achieve is not trivial. I am not aware of any distributed system similar to Celery that allows such thing.
The only way perhaps to do it is to dynamically create and run a new Celery worker with the new task added and configured the way you prefer...
You can register a task as:
def dynamic_task():
return "Hi"
dynamic_task = app.task(dynamic_task, name='my_name')
See that you can register a list of functions in this way, then you will need to restart the worker, however you can use the signals https://docs.celeryproject.org/en/stable/userguide/signals.html as well.
I've read Testing with Celery but I'm still a bit confused. I want to test code that generates a Celery task by running the task manually and explicitly, something like:
def test_something(self):
do_something_that_generates_a_celery_task()
assert_state_before_task_runs()
run_task()
assert_state_after_task_runs()
I don't want to entirely mock up the creation of the task but at the same time I don't care about testing the task being picked up by a Celery worker. I'm assuming Celery works.
The actual context in which I'm trying to do this is a Django application where there's some code that takes too long to run in a request, so, it's delegated to background jobs.
In test mode use CELERY_TASK_ALWAYS_EAGER = True. You can set this setting in your settings.py in django if you have followed the default guide for django-celery configuration.
Using Celery ver.3.1.23, I am trying to dynamically add a scheduled task to celery beat. I have one celery worker and one celery beat instance running.
Triggering a standard celery task y running task.delay() works ok. When I define a scheduled periodic task as a setting in configuration, celery beat runs it.
However what I need is to be able to add a task that runs at specified crontab at runtime. After adding a task to persistent scheduler, celery beat doesn't seem to detect the newly added new task. I can see that the celery-schedule file does have an entry with new task.
Code:
scheduler = PersistentScheduler(app=current_app, schedule_filename='celerybeat-schedule')
scheduler.add(name="adder",
task="app.tasks.add",
schedule=crontab(minute='*/1'),
args=(1,2))
scheduler.close()
When I run:
print(scheduler.schedule)
I get:
{'celery.backend_cleanup': <Entry: celery.backend_cleanup celery.backend_cleanup() <crontab: 0 4 * * * (m/h/d/dM/MY)>,
'adder': <Entry: adder app.tasks.add(1, 2) <crontab: */1 * * * * (m/h/d/dM/MY)>}
Note that app.tasks.add has the #celery.task decorator.
Instead of trying to find a good workaround, I suggest you switch to the Celery Redbeat.
You may solve your problem by enabling autoreloading.
However I'm not 100% sure it will work for your config file but it should if is in the CELERY_IMPORTS paths.
Hoverer note that this feature is experimental and to don't be used in production.
If you really want to have dynamic celerybeat scheduling you can always use another scheduler like the django-celery one to manage periodic tasks on db via a django admin.
I'm having a similar problem and a solution I thought about is to pre-define some generic periodic tasks (every 1s, every 5mins, etc) and then have them getting, from DB, a list of function to be executed.
Every time you want to add a new task you just add an entry in your DB.
Celery beat stores all the periodically scheduled tasks in the model PeriodicTask . As a beat task can be scheduled in different ways including crontab, interval or solar. All these fields are a foreign key in the PeriodicTask model.
In order to dynamically add a scheduled task, just populate the relevant models in celery beat, the scheduler will detect changes. The changes are detected when either the count of tuple changes or save() function is called.
from django_celery_beat.models import PeriodicTask, CrontabSchedule
# -- Inside the function you want to add task dynamically
schedule = CrontabSchedule.objects.create(minute='*/1')
task = PeriodicTask.objects.create(name='adder',
task='apps.task.add', crontab=schedule)
task.save()
I got celery project with RabbitMQ backend, that relies heavily on inspecting scheduled tasks. I found that the following code returns nothing for most of the time (of course, there are scheduled tasks) :
i = app.control.inspect()
scheduled = i.scheduled()
if (scheduled):
# do something
This code also runs from one of tasks, but I think it doesn't matter, I got same result from interactive python command line (with some exceptions, see below).
At the same time, celery -A <proj> inspect scheduled command never fails. Also, I noticed, that when called from interactive python command line for the first time, this command also never fails. Most of the successive i.scheduled() calls return nothing.
i.scheduled() guarantees result only when called for the first time?
If so, why and how then can I inspect scheduled tasks from task? Run dedicated worker and restart it after every task? Seems like overkill for such trivial task.
Please explain, how to use this feature the right way.
This is caused by some weird issue inside Celery app. To repeat methods from Inspect object you have to create new Celery app instance object.
Here is small snippet, which can help you:
from celery import Celery
def inspect(method):
app = Celery('app', broker='amqp://')
return getattr(app.control.inspect(), method)()
print inspect('scheduled')
print inspect('active')
I have a code which deletes an api column when executed. Now I want it to execute after some time lets say two weeks. Any idea or directions how do I implement it?
My code:
authtoken = models.UserApiToken.objects.get(api_token=token)
authtoken.delete()
This is inside a function and executed when a request is made.
There are two main ways to get this done:
Make it a custom management command, and trigger it through crontab.
Use celery, make it a celery task, and use celerybeat to trigger the job after 2 weeks.
I would recommend celery, as it provides a better control of your task queues and jobs.