> Exactly. For example, if one has to consider other things running on the same box and is only given 2 cores from 8 for computation purposes.

Got it, I can understand that use case. Do you use the scheduler plugin to replace the default so you gain control of the number of threads being used? That's the idea behind that scheduler plugin.

> But operators take a Scheduler, not a Scheduler.Worker. If I want channel everything to a single dedicated thread, there is no other option but to implement a custom Scheduler.

Did you use `Schedulers.executor` with a single thread up until 0.18?

I think `Schedulers.fixed(n)` would be confusing as it would create a new one each time that is invoked, so someone would have to make sure they invoke that only once and then use that reference everywhere. If we are going to add something like that I think we'd want `Schedulers.newFixed(n)` or something like that. 

That said, I think this borders on too nuanced to include in the default public API as it is really easy to use this incorrectly, which is something we've been working hard to solve with Schedulers.