MTurk: Get Multi-HIT Tasks Working

[gilbo]

As currently coded, each worker can perform at most one HIT (i.e. chunk of work) per experiment/task. While this is great for running actual experiments where we want to limit workers' exposure to the task, it's not so great if we want to let workers get into a groove building scenes or what have you.

However, the system has the appropriate parameters exposed and models available to allow for issuing multiple HITs per Task.

To accomplish this change, take a look at the 'app/models/mt_task.rb' file. If you look at where the HIT is submitted and then logged in the DB, you should see how to launch multiple HITs instead.

Getting this to work right involves two tricky bits:

1. You need to test this reasonably thoroughly on the sandbox to make sure it's behaving in the way you think it is. You should also check to make sure that the existing task methods (like complete!) still work correctly with multiple HITs.
2. In order to totally de-couple the desired number of assignments completed from the max number completed by any given worker, you will need some daemon/cron-job or something that detects when the desired number of assignments have been completed or accepted, and then tells the task to expire.