Introduction to Effect, Michael Arnaldi, WorkerConf 2022 Dornbirn

Introduction to Effect, Michael Arnaldi, WorkerConf 2022 Dornbirn

Concurrency

We can have multiple ways to handle concurrency:

Simple Promise.all

Promise.all but for each N items, awaiting to resolve the N first to not blow the API

Always having N API calls at the same time running (a lot complex)

Sometimes we want to have the option to interrupt the api calls

And the option to retry when an error occur

And the list goes one...

• Logging
• Metrics
• Tracing
• Dependency Injection
• Etc

PS: Most of the code shown is hard to understand and hard to maintain

Effect

The code before is hard to compose together, this is one point of why effect ts was created.

Effect is a lazy promise, describes your intention, and you execute the start after the configuration (effect to a fiber). This makes possible composability and higher order behaviour.

Let's redo those codes with effect!

It's good to create a file that exports what you need:

PS: never it's the list of requirements it needs to run the effect

PS: unsafeRunAsyncWith is a helper function that wraps errors we don't expect to happen

What Effect provide for us?