This is a third blog post about Reactive Programming in Scala. The first two blog posts, Reactive Programming: Try versus Future resp. Reactive Programming: Notification versus Observable, covered reactive programs resulting in one value resp. many values. This blog post covers schedulers and workers. They are used to transform iterables to observables. As mentioned in Reactive Programming: Notification versus Observable, the transformation from iterables to observables is not as trivial as it looks: at any moment subscribed observers should be able to unsubscribe.