Currently, Beaker uses a fairly simply custom scheduling system that repeatedly scans over all queued recipes and tries to assign each one to a currently free host.
Some RFEs are currently impossible to implement given the simplicity of the scheduling model.
This RFE is being added in order to more easily capture which bugs are blocked by that.
One proposal to improve the situation is captured in https://beaker-project.org/dev/proposals/event-driven-scheduler.html
As noted in the deferral of that proposal, another option is to switch away from running a custom scheduler, and instead adopt the Apache Mesos meta-scheduling framework for Beaker's resource management: https://mesos.apache.org/
The latter approach seems desirable (doing scheduling well is difficult, and Mesos provides a lot of useful infrastructure), but what Beaker does is a little odd from the perspective of most resource management systems (we don't just need "a computer", we need to get very, very specific, down to the level of identifying specific models of harddrive controller, or network card).
This is currently stalled on lack of time to continue the investigation.
Ray, could I get you to provide a summary of where you got to with your research here?
https://lists.fedorahosted.org/pipermail/beaker-devel/2014-May/000997.html was my decision to defer the existing design proposals, but I didn't publish a lot in the way of technical details.
Since Raymond departed, I think I can at least clear the NEEDINFO flag.