def get_consumers(self, connection):
    return [Consumer(connection.channel(), queues=[self.queue], callbacks=[
        self.on_message])]

def on_message(self, body, message):
    print('GOT MESSAGE: %r' % (body,))
message.ack()
celery = Celery(broker='amqp://localhost//')
celery.steps['consumer'].add(CustomConsumer)
celery.user_options['worker'].add(Option('--enable-custom-consumer', action
    ='store_true', help='Enable our custom consumer.'))
Использование Celery с существующими сообщениями RabbitMQ