Print statement in Celery scheduled task doesn't appear in terminal

Question

When I run celery -A tasks2.celery worker -B I want to see “celery task” printed every second. Currently nothing is printed. Why isn’t this working?

from app import app
from celery import Celery
from datetime import timedelta

celery = Celery(app.name, broker='amqp://guest:@localhost/', backend='amqp://guest:@localhost/')
celery.conf.update(CELERY_TASK_RESULT_EXPIRES=3600,)

@celery.task
def add(x, y):
    print "celery task"
    return x + y

CELERYBEAT_SCHEDULE = {
    'add-every-30-seconds': {
        'task': 'tasks2.add',
        'schedule': timedelta(seconds=1),
        'args': (16, 16)
    },
}

This is the only output after staring the worker and beat:

[tasks]
  . tasks2.add

[INFO/Beat] beat: Starting...
[INFO/MainProcess] Connected to amqp://guest:**@127.0.0.1:5672//
[INFO/MainProcess] mingle: searching for neighbors
[INFO/MainProcess] mingle: all alone

Asked By: huhh hhbhb

||

Source

Answer 1

Make sure you run celery beat worker for scheduled tasks:

celery beat --app app.celery

Check the docs here: http://celery.readthedocs.org/en/latest/userguide/periodic-tasks.html#starting-the-scheduler

Answered By: gonz

Answer 2

You wrote the schedule, but didn’t add it to the celery config. So beat saw no scheduled tasks to send. The example below uses celery.config_from_object(__name__) to pick up config values from the current module, but you can use any other config method as well.

Once you configure it properly, you will see messages from beat about sending scheduled tasks, as well as the output from those tasks as the worker receives and runs them.

from celery import Celery
from datetime import timedelta

celery = Celery(__name__)
celery.config_from_object(__name__)

@celery.task
def say_hello():
    print('Hello, World!')

CELERYBEAT_SCHEDULE = {
    'every-second': {
        'task': 'example.say_hello',
        'schedule': timedelta(seconds=5),
    },
}

$ celery -A example.celery worker -B -l info

[tasks]
  . example.say_hello

[2015-07-15 08:23:54,350: INFO/Beat] beat: Starting...
[2015-07-15 08:23:54,366: INFO/MainProcess] Connected to amqp://guest:**@127.0.0.1:5672//
[2015-07-15 08:23:54,377: INFO/MainProcess] mingle: searching for neighbors
[2015-07-15 08:23:55,385: INFO/MainProcess] mingle: all alone
[2015-07-15 08:23:55,411: WARNING/MainProcess] celery@netsec-ast-15 ready.
[2015-07-15 08:23:59,471: INFO/Beat] Scheduler: Sending due task every-second (example.say_hello)
[2015-07-15 08:23:59,481: INFO/MainProcess] Received task: example.say_hello[2a9d31cb-fe11-47c8-9aa2-51690d47c007]
[2015-07-15 08:23:59,483: WARNING/Worker-3] Hello, World!
[2015-07-15 08:23:59,484: INFO/MainProcess] Task example.say_hello[2a9d31cb-fe11-47c8-9aa2-51690d47c007] succeeded in 0.0012782540870830417s: None

Answered By: davidism

Answer 3

In version 4.1.0 you have to add logger to your task.py file like so:

from celery.utils.log import get_task_logger

logger = get_task_logger(__name__)


@task(name="multiply_two_numbers")
def mul(x, y):
    total = x * (y * random.randint(3, 100))
    #HERE:
    logger.info('Adding {0} + {1}'.format(x, y))
    return total

Stated halfway down in the docs here if you want more info:
http://docs.celeryproject.org/en/latest/userguide/tasks.html

Answered By: B-Tron of the Autobots

Answer 4

I actually had issues printing mine on command prompt because I was using the wrong command but I found a link to a project which I forked Project

(If on Mac ) celery -A Project worker --loglevel=info
(If on Windows) celery -A Project worker -l info --pool=solo

Answered By: Codertjay

Answer 5

I know it’s an old thread, but for those running into it… please check your app config. Make sure "TESTING" is set to "False". In my case it’s a Flask APP, also I am updating the celery config with Flask app config

celery.conf.update(app.config)

but just make sure TESTING is not set to "True",

Answered By: Ozzie Ghani

Print statement in Celery scheduled task doesn't appear in terminal

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