Excerpts from Steven Lawrance's message of Fri Jan 06 08:48:35 +1000 2012:
So if we can't distinguish not being able to provision a particular recipe via RHEV "right now" as opposed to "never (with current resources)", then we at least need a cheap way to determine the former in order to avoid a bottleneck in the scheduler.
That is, when a job is submitted, we want to determine whether it _can_ be satisfied by RHEV without then restricting it to RHEV and preventing it from going to baremetal hardware in the lab.
Does Beaker even need to care about the difference between "right now" and "never"? If a recipe can't be provisioned by RHEV "right now", whether because RHEV's resources are temporarily exhausted or the recipe could never fit, shouldn't Beaker then try to provision it on real hardware immediately? Otherwise we could end up with recipes queued waiting for RHEV while real hardware sits idle.