Dynamically obtain addresses and statuses from wogrkers for worker-based engine for taskflow

Worker-based engine should be able to dynamically obtain information about workers, inluding: - service discovery: where the workers are available and what each of them can do - status: what is each worker doing (which tasks are running on it right now) This should be done in a way that does not affect, or better i...

Instead of exposing raw green threads, hide them. for OpenStack Compute (nova)

Currently there are places in nova which expose and use the greenthread code directly for various reasons. It would be nice to move to a more abstracted model where the greenthread implementation is only exposed in 'utils.py' and everything else uses modules/code there instead of using greenthread directly. This see...