Understanding how tasks are imported

Behind-the-scenes when you decorate a function with task() or periodic_task(), the function registers itself with a centralized in-memory registry. When that function is called, a reference is put into the queue (among other things), and when that message is consumed the function is then looked-up in the consumer’s registry. Because of the way this works, it is strongly recommended that all decorated functions be imported when the consumer starts up.

Note

If a task is not recognized, the consumer will throw a QueueException

The consumer is executed with a single required parameter – the import path to a Huey object. It will import the object along with anything else in the module – thus you must be sure imports of your tasks should also occur with the import of the Huey object.

Suggested organization of code

Generally, I structure things like this, which makes it very easy to avoid circular imports. If it looks familiar, that’s because it is exactly the way the project is laid out in the getting started guide.

• config.py, the module containing the Huey object.

  # config.py
  from huey import RedisHuey
  
  huey = RedisHuey('testing', host='localhost')
  

• tasks.py, the module containing any decorated functions. Imports the huey object from the config.py module:

  # tasks.py
  from config import huey
  
  @huey.task()
  def count_beans(num):
      print 'Counted %s beans' % num
  

• main.py / app.py, the “main” module. Imports both the config.py module and the tasks.py module.

  # main.py
  from config import huey  # import the "huey" object.
  from tasks import count_beans  # import any tasks / decorated functions
  
  
  if __name__ == '__main__':
      beans = raw_input('How many beans? ')
      count_beans(int(beans))
      print 'Enqueued job to count %s beans' % beans
  

To run the consumer, point it at main.huey, in this way everything gets imported correctly:

$ huey_consumer.py main.huey