Develop Reference

How to fix receiving unregistered task error - Celery

I am trying to establish a periodic task using Celery (4.2.0) and RabbitMQ (3.7.14) running with Python 3.7.2 on an Azure VM using Ubuntu 16.04. I am able to start the beat and worker and see the message get kicked off from beat to the worker but at this point I'm met with an error like so
[2019-03-29 21:35:00,081: ERROR/MainProcess] Received
unregistered task of type 'facebook-call.facebook_api'.
The message has been ignored and discarded.
Did you remember to import the module containing this task?
Or maybe you're using relative imports?
My code is as follows:
from celery import Celery
from celery.schedules import crontab
app = Celery('facebook-call', broker='amqp://localhost//')
#app.task
def facebook_api():
{function here}
app.conf.beat.schedule = {
'task': 'facebook-call.facebook_api',
'schedule': crontab(hour=0, minute =0, day='0-6'),
}
I am starting the beat and worker processes by using the name of the python file which contains all of the code
celery -A FacebookAPICall beat --loglevel=info
celery -A FacebookAPICall worker --loglevel=info
Again, the beat process starts and I can see the message being successfully passed to the worker but cannot figure out how to "register" the task so that it is processed by the worker.

I was able to resolve the issue by renaming the app from facebook-call to coincide with the name of the file FacebookAPICall
Before:
app = Celery('facebook-call', broker='amqp://localhost//'
After:
app = Celery('FacebookAPICall', broker='amqp://localhost//'
From reading the Celery documentation, I don't totally understand why the name of the app must also be the name of the .py file but that seems to do the trick.

Celery Async Tasks and Periodic Tasks together

Unable to run periodic tasks along with asynchronous tasks together. Although, if I comment out the periodic task, asynchronous tasks are executed fine, else asynchronous tasks are stuck.
Running: celery==4.0.2, Django==2.0, django-celery-beat==1.1.0, django-celery-results==1.0.1
Referred: https://github.com/celery/celery/issues/4184 to choose celery==4.0.2 version, as it seems to work.
Seems to be a known issue
https://github.com/celery/django-celery-beat/issues/27
I've also done some digging the ONLY way I've found to get it back to
normal is to remove all periodic tasks and restart celery beat. ~ rh0dium
celery.py
import django
import os
from celery import Celery
# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'bid.settings')
# Setup django project
django.setup()
app = Celery('bid')
# Using a string here means the worker don't have to serialize
# the configuration object to child processes.
# - namespace='CELERY' means all celery-related configuration keys
# should have a `CELERY_` prefix.
app.config_from_object('django.conf:settings', namespace='CELERY')
# Load task modules from all registered Django app configs.
app.autodiscover_tasks()
settings.py
INSTALLED_APPS = (
...
'django_celery_results',
'django_celery_beat',
)
# Celery related settings
CELERY_BROKER_URL = 'redis://localhost:6379/0'
CELERY_BROKER_TRANSPORT_OPTIONS = {'visibility_timeout': 43200, }
CELERY_RESULT_BACKEND = 'django-db'
CELERY_ACCEPT_CONTENT = ['application/json']
CELERY_RESULT_SERIALIZER = 'json'
CELERY_TASK_SERIALIZER = 'json'
CELERY_CONTENT_ENCODING = 'utf-8'
CELERY_ENABLE_REMOTE_CONTROL = False
CELERY_SEND_EVENTS = False
CELERY_TIMEZONE = 'Asia/Kolkata'
CELERY_BEAT_SCHEDULER = 'django_celery_beat.schedulers:DatabaseScheduler'
Periodic task
#periodic_task(run_every=crontab(hour=7, minute=30), name="send-vendor-status-everyday")
def send_vendor_status():
return timezone.now()
Async task
#shared_task
def vendor_creation_email(id):
return "Email Sent"
Async task caller
vendor_creation_email.apply_async(args=[instance.id, ]) # main thread gets stuck here, if periodic jobs are scheduled.
Running the worker, with beat as follows
celery worker -A bid -l debug -B
Please help.

Here are a few observations, resulted from multiple trial and errors, and diving into celery's source code.
#periodic_task is deprecated. Hence it would not work.
from their source code:
#venv36/lib/python3.6/site-packages/celery/task/base.py
def periodic_task(*args, **options):
"""Deprecated decorator, please use :setting:`beat_schedule`."""
return task(**dict({'base': PeriodicTask}, **options))
Use UTC as base timezone, to avoid timezone related confusions later on. Configure periodic task to fire on calculated times with respect to UTC. e.g. for 'Asia/Calcutta' reduce the time by 5hours 30mins.
Create a celery.py as follows:
celery.py
import django
import os
from celery import Celery
# set the default Django settings module for the 'celery' program.
from celery.schedules import crontab
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'proj.settings')
# Setup django project
django.setup()
app = Celery('proj')
# Using a string here means the worker don't have to serialize
# the configuration object to child processes.
# - namespace='CELERY' means all celery-related configuration keys
# should have a `CELERY_` prefix.
app.config_from_object('django.conf:settings', namespace='CELERY')
# Load task modules from all registered Django app configs.
app.autodiscover_tasks()
app.conf.beat_schedule = {
'test_task': {
'task': 'test_task',
'schedule': crontab(hour=2,minute=0),
}
}
and task could be in tasks.py under any app, as follows
#shared_task(name="test_task")
def test_add():
print("Testing beat service")
Use celery worker -A proj -l info and celery beat -A proj -l info for worker and beat, along with a broker e.g. redis. and this setup should work fine.

Celery autoscale not executing tasks

When Celery is receiving a Task, this task never gets executed, just hangs:
These tasks arrive randomly, in very low load.
Celery 3.1.20
[2016-03-02 22:33:08,300: INFO/MainProcess] Received task: catalogue.cluster.deploy_cluster.imbue_cluster[A5C030C4E0]
[2016-03-02 22:33:08,303: INFO/MainProcess] Scaling up 1 processes.
After this, nothing happens.
I started celery with supervisord using a shell script:
source ~/.profile
CELERY_LOGFILE=/usr/local/src/imbue/application/imbue/log/celeryd.log
CELERYD_OPTS=" --loglevel=INFO --autoscale=10,5"
cd /usr/local/src/imbue/application/imbue/conf
exec celery worker -n celeryd#%h -f $CELERY_LOGFILE $CELERYD_OPTS
My configuration:
CELERYD_CHDIR=settings.filepath
CELERY_IGNORE_RESULT = False
CELERY_RESULT_BACKEND = "amqp"
CELERY_TASK_RESULT_EXPIRES = 360000
CELERY_RESULT_PERSISTENT = True
BROKER_URL=<rabbitmq>
CELERY_ENABLE_UTC=True
CELERY_TIMEZONE= "US/Eastern"
CELERY_IMPORTS=("catalogue.cluster.deploy_cluster",
"tools.deploy_tools",)
This is how I call my tasks:
celery = Celery()
celery.config_from_object('conf.celeryconfig')
celery.send_task("catalogue.cluster.deploy_cluster.imbue_cluster",
kwargs={'configuration': configuration,
'job': job_instance,
'api_call': True},
task_id=job_instance.reference)
#task(bind=True, default_retry_delay=300, max_retries=5)
def imbue_cluster(...)
Similar issues:
http://comments.gmane.org/gmane.comp.python.amqp.celery.user/4990
https://groups.google.com/forum/#!topic/cloudify-users/ANvSv7mV7h4

Turn off Celery task delay on development server

I'm using Celery on Heroku with RabbitMQ and the following settings:
# settings.py
DEFAULT_AMQP = "amqp://guest:guest#localhost//"
BROKER_URL = os.getenv('CLOUDAMQP_URL', DEFAULT_AMQP)
CELERY_TASK_SERIALIZER = 'pickle'
CELERY_RESULT_SERIALIZER = 'json'
CELERY_ENABLE_UTC = True
CELERY_STORE_ERRORS_EVEN_IF_IGNORED = True
CELERY_RESULT_BACKEND = False
BROKER_POOL_LIMIT = 5
# trying to clean up this memory leak
CELERYD_MAX_TASKS_PER_CHILD = 5
CELERYD_TASK_TIME_LIMIT = 60*10 # time limit in seconds--watch if we end up throwing big tasks onto this
I generally call tasks using .delay().
On Heroku, I'd have to provision a separate worker dyno to handle these queued processes. For the development server, I'd like to still call my delayed tasks, but do it in the same thread rather than defer it to a worker queue. This means that every time I call .delay(), on the staging server, I want not to delay the task but actually just to call it as if I had used the normal .__call__() method.
Is there a Celery setting or some other way that I can basically turn Celery off and have calls to .delay() pass to .__call__() instead?

set CELERY_ALWAYS_EAGER to True for the dev env: http://celery.readthedocs.org/en/latest/configuration.html#celery-always-eager

Django/Celery multiple queues on localhost - routing not working

I followed celery docs to define 2 queues on my dev machine.
My celery settings:
CELERY_ALWAYS_EAGER = True
CELERY_TASK_RESULT_EXPIRES = 60 # 1 mins
CELERYD_CONCURRENCY = 2
CELERYD_MAX_TASKS_PER_CHILD = 4
CELERYD_PREFETCH_MULTIPLIER = 1
CELERY_CREATE_MISSING_QUEUES = True
CELERY_QUEUES = (
Queue('default', Exchange('default'), routing_key='default'),
Queue('feeds', Exchange('feeds'), routing_key='arena.social.tasks.#'),
)
CELERY_ROUTES = {
'arena.social.tasks.Update': {
'queue': 'fs_feeds',
},
}
i opened two terminal windows, in virtualenv of my project, and ran following commands:
terminal_1$ celery -A arena worker -Q default -B -l debug --purge -n deafult_worker
terminal_2$ celery -A arena worker -Q feeds -B -l debug --purge -n feeds_worker
what i get is that all tasks are being processed by both queues.
My goal is to have one queue to process only the one task defined in CELERY_ROUTES and default queue to process all other tasks.
I also followed this SO question, rabbitmqctl list_queues returns celery 0, and running rabbitmqctl list_bindings returns exchange celery queue celery [] twice. Restarting rabbit server didn't change anything.

Ok, so i figured it out. Following is my whole setup, settings and how to run celery, for those who might be wondering about same thing as my question did.
Settings
CELERY_TIMEZONE = TIME_ZONE
CELERY_ACCEPT_CONTENT = ['json', 'pickle']
CELERYD_CONCURRENCY = 2
CELERYD_MAX_TASKS_PER_CHILD = 4
CELERYD_PREFETCH_MULTIPLIER = 1
# celery queues setup
CELERY_DEFAULT_QUEUE = 'default'
CELERY_DEFAULT_EXCHANGE_TYPE = 'topic'
CELERY_DEFAULT_ROUTING_KEY = 'default'
CELERY_QUEUES = (
Queue('default', Exchange('default'), routing_key='default'),
Queue('feeds', Exchange('feeds'), routing_key='long_tasks'),
)
CELERY_ROUTES = {
'arena.social.tasks.Update': {
'queue': 'feeds',
'routing_key': 'long_tasks',
},
}
How to run celery?
terminal - tab 1:
celery -A proj worker -Q default -l debug -n default_worker
this will start first worker that consumes tasks from default queue. NOTE! -n default_worker is not a must for the first worker, but is a must if you have any other celery instances up and running. Setting -n worker_name is the same as --hostname=default#%h.
terminal - tab 2:
celery -A proj worker -Q feeds -l debug -n feeds_worker
this will start second worker that consumers tasks from feeds queue. Notice -n feeds_worker, if you are running with -l debug (log level = debug), you will see that both workers are syncing between them.
terminal - tab 3:
celery -A proj beat -l debug
this will start the beat, executing tasks according to the schedule in your CELERYBEAT_SCHEDULE.
I didn't have to change the task, or the CELERYBEAT_SCHEDULE.
For example, this is how looks my CELERYBEAT_SCHEDULE for the task that should go to feeds queue:
CELERYBEAT_SCHEDULE = {
...
'update_feeds': {
'task': 'arena.social.tasks.Update',
'schedule': crontab(minute='*/6'),
},
...
}
As you can see, no need for adding 'options': {'routing_key': 'long_tasks'} or specifying to what queue it should go. Also, if you were wondering why Update is upper cased, its because its a custom task, which are defined as sub classes of celery.Task.
Update Celery 5.0+
Celery made a couple changes since version 5, here is an updated setup for routing of tasks.
How to create the queues?
Celery can create the queues automatically. It works perfectly for simple cases, where celery default values for routing are ok.
task_create_missing_queues=True or, if you're using django settings and you're namespacing all celery configs under CELERY_ key, CELERY_TASK_CREATE_MISSING_QUEUES=True. Note, that it is on by default.
Automatic scheduled task routing
After configuring celery app:
celery_app.conf.beat_schedule = {
"some_scheduled_task": {
"task": "module.path.some_task",
"schedule": crontab(minute="*/10"),
"options": {"queue": "queue1"}
}
}
Automatic task routing
Celery app still has to be configured first and then:
app.conf.task_routes = {
"module.path.task2": {"queue": "queue2"},
}
Manual routing of tasks
In case and you want to route the tasks dynamically, then when sending the task specify the queue:
from module import task
def do_work():
# do some work and launch the task
task.apply_async(args=(arg1, arg2), queue="queue3")
More details re routing can be found here:
https://docs.celeryproject.org/en/stable/userguide/routing.html
And regarding calling tasks here:
https://docs.celeryproject.org/en/stable/userguide/calling.html

In addition to accepted answer, if anyone comes here and still wonders why his settings aren't working (as I did just moments ago), here's why: celery documentation isn't listing settings names properly.
For celery 5.0.5 settings CELERY_DEFAULT_QUEUE, CELERY_QUEUES, CELERY_ROUTES should be named CELERY_TASK_DEFAULT_QUEUE, CELERY_TASK_QUEUESand CELERY_TASK_ROUTES instead. These are settings that I've tested, but my guess is the same rule applies for exchange and routing key aswell.