Arvados

Sometimes spot instances are not available, but we don't want to sacrifice turnaround time by waiting excessively long time for spot instance price/availability to come down. In that case, the user would like fall back on requesting a regular on demand instance.

Consider how the user should request this behavior (this should probably be controllable per-workflow), and what conditions Arvados decides to fall back to on demand.

Thought: could be done by adding on demand instances to the list of candidate instance types after trying all the spot instance types.