How do I bind a Celery task to a specific queue? - celery

Question

I want to write a task that is only executable from within a given queue - if somebody tries to pass a different queue into the routing_key parameter of apply_async I want to raise an exception. How do I do this?

Answer 1

You could write your own task that would check to make sure a valid routing key is being passed in when apply_async is being called. You can also apply this to queues. Set up routes and queues in your config:
import celery
from kombu import Queue, Exchange
app = celery.Celery('app')
app.conf.CELERY_QUEUES = (
Queue('add', Exchange('default'), routing_key='good'),
)
app.conf.CELERY_ROUTES = {
'app.add': {
'queue': 'add',
'routing_key': 'good'
}
}
Now, create your own Task class that will perform the check on the routing key. You'll need to override apply_async:
class RouteCheckerTask(celery.Task):
abstract = True
def apply_async(self, args=None, kwargs=None, task_id=None, producer=None,
link=None, link_error=None, **options):
app = self._get_app()
routing_key = options.get('routing_key', None)
if routing_key:
valid_routes = [v['routing_key'] for k, v in app.conf.CELERY_ROUTES.items()]
is_valid = routing_key in valid_routes
if not is_valid:
raise NotImplementedError('{} is not a valid routing key. Options are: {}'.format(routing_key, valid_routes))
if app.conf.CELERY_ALWAYS_EAGER:
return self.apply(args, kwargs, task_id=task_id or uuid(), link=link, link_error=link_error, **options)
# add 'self' if this is a "task_method".
if self.__self__ is not None:
args = args if isinstance(args, tuple) else tuple(args or ())
args = (self.__self__, ) + args
return app.send_task(
self.name, args, kwargs, task_id=task_id, producer=producer,
link=link, link_error=link_error, result_cls=self.AsyncResult,
**dict(self._get_exec_options(), **options)
)
Base your tasks from this one and call apply_async normally:
#app.task(base=RouteCheckerTask)
def add(x, y):
return x + y
# Fails
add.apply_async([1, 2], routing_key='bad')
# Passes
add.apply_async([1, 2], routing_key='good')