Summary:
data_workers.py provides a really nice, easy way to run background threads for data input. Unfortunately, it's restrictive, the output of the fetcher function has to be a numpy array.
I pulled out that core nice thread management into parallel_workers, and updated the classes data_workers to extend those classes. The main change was refactoring out most of the queue handling logic into QueueManager.
This way parallel_workers can be used to manage background threads without having to use the queue for output.
Reviewed By: akyrola
Differential Revision: D5538626
fbshipit-source-id: f382cc43f800ff90840582a378dc9b86ac05b613
