This interface manages task reservations. Reservations are used to guarantee space in a scheduler for tasks. Once a reservation is acquired, the associated tasks will always have space to run. Acquiring a reservation does not actually schedule the tasks, so until
use
is called, the tasks will never run. The reservation may be cancelled if it has not yet been run, and no cost will be charged to the owner.
If this reservation includes tasks scheduled to be run at a specified time, and that time has already passed when use
is called, then the tasks are run immediately.