MRI Fibers are not green threads, they are coroutes that the developer has to manage when to release the lock. (Green threads on the other hand would be scheduled by the runtime) But there is work in progress to make something like green threads available in MRI Ruby. I linked to the redmine ticket at the end of the article (Auto::Thread)

This article was only talking about:

• concurrency in one process (therefore I didn’t mention how to use multiple processes
• concurrency withoout any external gem (therefore I didn’t mention EventMachine and co)

It might be a bit missleading, so I will make it clear at the beginning. Thanks!