requests-scala VS Http4s

There's the Li Haoyi's ecosystem of tools and libraries that's fun to hack on, has a low entry-bar (with a design philosophy of using the least complex abstractions for the job), and has few libs like requests and cask that may appeal to those liking some python minimalism. That's not the fastest way to learn hardcore FP, that's not the worst either.

Another thing that caught my attention is the choice for HTTP client. If the authors wanted to go with the simplest thing, they could have picked requests-scala (from the com-lihaoyi family of libraries). If they wanted to go with full blown Scala FP, they could have chosen http4s client (Ember). Sttp awkwardly sits in the middle being neither.

Finally, to give you an example of how simple Scala can be when you get rid of all the fancy stuff, take a look at the examples in Li Haoyi's requests-scala library, a port of the excellent requests Python library. I challenge anyone to call that code complex.

http4s (either with Blaze or Ember) is great, but you may need to think a bit about what you're doing. Maybe https://github.com/com-lihaoyi/requests-scala will be the best choice for your particular situation?

http4s is a Typelevel project, and therefore falls into the "program in Scala as if it were Haskell" category. Many people find this off-putting, but honestly, I think with the resources listed above, this is the option at the best intersection of "mature" and "well-documented" available in Scala. The reason it's off-putting to many people is that Haskell-style pure FP isn't mainstream, so it isn't so much a matter of learning a new technology as it is a matter of learning a new paradigm, which necessarily means surfacing and unlearning things you already know, and perhaps confronting the uncomfortable feeling that things you thought were "fundamental," "have to be that way," aren't, and don't. I personally found this process liberating. But not everyone does.

If you want a mature REST API library, I recommend http4s. Be aware, though, that it’s based on purely-functional programming with Cats, cats-effect, and fs2, so if you’re not familiar with them or aren’t prepared to commit to the paradigm, the learning curve may be daunting, seem pointless, or both.

See also cats-effect and fs2. cats-effect gives you your IO Monad (and IOApp to run it with on supported platforms). fs2 is the ecosystem’s streaming library, which is much more pervasive in functional Scala than in Haskell. For example, http4s and Doobie are both based on fs2.

Most important/known: * https://http4s.org/ - an HTTP client/server * https://github.com/typelevel/fs2 - streaming * https://github.com/tpolecat/doobie - JDBC

Scala devs are too busy wondering about free monads and F[Request[F] => Response[F]]. I am very pleased by http4s, Doobie, ScalaJS, and the whole ecosystem, really: https://http4s.org

In reality, your performance issues will not be http4s, but something else. That being said, there are improvements that http4s can and is making, and I'm quite excited about the future 1.0 release, which has some important and fundamental performance improvements already, like a a 125% performance improvement on the plaintext benchmark from https://github.com/http4s/http4s/pull/6091 - and finally, yes, akka-http does have very good performance, but you can also get good performance out of http4s.

http4s for REST services.

This is a long list of misunderstandings I don’t have the patience to unpack. Instead, let me refer you to the links in my top comment in the thread, then suggest you learn at least http4s, a purely-functional web service library that’s been used in production for a decade or so now.

The most popular nowadays are - I guess - akka-http and http4s. You can also use Play if you don't want to start from scratch but prefer a framework-based approach.

There are functional frameworks: https://http4s.org/