Question

Under some conditions, I want to make a celery task fail from within that task. I tried the following:

from celery.task import task
from celery import states

@task()
def run_simulation():
    if some_condition:
        run_simulation.update_state(state=states.FAILURE)
        return False

However, the task still reports to have succeeded:

Task sim.tasks.run_simulation[9235e3a7-c6d2-4219-bbc7-acf65c816e65]
succeeded in 1.17847704887s: False

It seems that the state can only be modified while the task is running and once it is completed – celery changes the state to whatever it deems is the outcome (refer to this question). Is there any way, without failing the task by raising an exception, to make celery return that the task has failed?

Answer 1

I got an interesting reply on this question from Ask Solem, where he proposes an ‘after_return’ handler to solve the issue. This might be an interesting option for the future.

In the meantime I solved the issue by simply returning a string ‘FAILURE’ from the task when I want to make it fail and then checking for that as follows:

result = AsyncResult(task_id)
if result.state == 'FAILURE' or (result.state == 'SUCCESS' and result.get() == 'FAILURE'):
    # Failure processing task