Python Celery子任务组未执行

Question

I'm trying to use Celery to handle background tasks. I currently have the following setup:

@app.task
def test_subtask(id):
    print('test_st:', id)


@app.task
def test_maintask():
    print('test_maintask')
    g = group(test_subtask.s(id) for id in range(10))
    g.delay()

test_maintask is scheduled to execute every n seconds, which works (I see the print statement appearing in the command line window where I started the worker). What I'm trying to do is have this scheduled task spawn a series of subtasks, which I've grouped here using group() .

It seems, however, like none of the test_subtask tasks are being executed. What am I doing wrong? I don't have any timing/result constraints for these subtasks and just want them to happen some time from now, asynchronously, in no particular order. n seconds later, test_maintask will fire again (and again) but with none of the subtasks executing.

I'm using one worker, one beat, and AMQP as a broker (on a separate machine).

EDIT : For what it's worth, the problem seems to be purely because of one task calling another (and not something because of the main task being scheduled). If I call the main task manually:

celery_funcs.test_maintask.delay()

I see the main task's print statement but -- again -- not the subtasks. Calling a subtask directly does work however:

celery_funcs.test_subtask.delay(10)

Answer 1

Sigh... just found out the answer, I used the following to configure my Celery app:

app = Celery('celery_app', broker='<my_broker_here>')

Strangely enough, this is not being picked up in the task itself... that is,

print('test_maintask using broker', app.conf.BROKER_URL, current_app.conf.BROKER_URL)

Gives back '<my_broker_here>' and None respectively, causing the group to be send of to... some default broker (I guess?).

Adding BROKER_URL to app.conf.update does the trick, though I'm still not completely clear on what's going on in Celery's internals here...