Report on worker "load" (the number of workers being used over
time). Reruns an object of class worker_load, for which a
mean method exists (this function is a work in progress and the
interface may change).
rrq_worker_load(worker_ids = NULL, controller = NULL)Optional vector of worker ids. If NULL then
all active workers are used.
The controller to use. If not given (or NULL)
we'll use the controller registered with
rrq_default_controller_set().
An object of class "worker_load", which has a pretty print method.