kebab-case: Understanding thread pools through cats-effect- overview

Could not find an implicit IORuntime. is a common error when using cats-effect. But what is an IORuntime, and how should we use it? In this tutorial, you’ll use cats-effect 3 to explore the basics of thread pools, execution contexts, and blocking. You’ll see why the cats-effect IORuntime.global is the best model for your application.

You will learn

The difference between blocking and compute‑intensive operations.
What a thread pool is; and about bounded and unbounded thread pools.
What the IORuntime is made of, and why cats-effect 3 structures it the way it does.
When you should use the IORuntime.global (and when you shouldn’t)

I assume you know

A bit about the cats effect IO datatype, to the extent that you can create and run an IO.
A bit about concurrency such that you’re not too surprised by parallel computations.

You’ll get the most out of this if cats-effect is your first experience of threads. You’re not too sure what thread pools are (or execution contexts, for that matter), and aren’t as confident in using them as you’d like.

Some caveats

This tutorial won’t teach you how to use cats-effect — and you certainly don’t need to understand thread pools in order to use it. If you’re still getting started with IO and the basics of parallelism, why not head over to the cats-effect tutorial instead?