Akka VS Http4s

Kotlin also has a construct for asynchronous collections/streams. Kotlin's version of AsyncSequence is called a Flow. Just as Swift's AsyncSequence builds upon prior experience with RxSwift and Combine, Kotlin's Flow APIs build upon earlier stream/collection APIs in the JVM ecosystem: Java's RxJava, Java8 Streams, Project Reactor, and Scala's Akka.

First-class distributed and multicore computing. Swift has first-class “actors” and “distributed” methods. Unison, Erlang, and Elixir are built with distributed being one of the #1 concerns. Though first-class is not super common and I don't really expect it to be because usually libraries are enough (e.g. Scala has Akka and is used WIDELY for distributed); whereas something like linear types and typed effects, you can't emulate in a library.

Akka is a library that implements the actor model for JVM languages. Mainly in Scala, but you can use it in Java too, and maybe others. It doesn't feel as ergonomic as Elixir, but if Elixir is too "out there" for the decision makers in your case, this might be a friendlier alternative.

Kalix builds on the lessons we have learned from more than a decade of building Akka (leveraging the actor model) and our experience helping large (and small) enterprises move to the cloud and use it in the most time, cost, and resource-efficient way possible.

Note Akka, the Java & friends framework, is working with the actor model and have as main inspiration Erlang to mimic some features of the BEAM on top of the JVM.

Looking back at real dates, I started learning the language (Scala) back in 2008 because it was something new and trendy that interested me. I started spending some serious time with it in 2009 (helping out other newcomers and making small contributions to various projects), and then in 2010 became a core contributor to the Akka project (you can find me a little ways down this list: https://github.com/akka/akka/graphs/contributors). For the most part I worked on the features I wanted to, but worked on other things if a user asked nicely. Akka became very popular in the early 2010s, so all of a sudden I had highly sought after skills. Got hired by a London based company and moved myself and my family from Canada over here. But even today, that exposure I got 10 years ago still helps me to land new contracts.

In the open source world, Akka, the most popular actor system library in the JVM ecosystem, that’s heavily used in tonnes of open source projects, recently went from “free and open source” to “paid/proprietary and source available.” https://github.com/akka/akka/pull/31561

Same strategy - the pricing is insanely high (for a library), and the project is effectively dead now, but it’ll take some larger enterprises awhile to move away from.

Lightbend, the company owning Akka, recently shared a blog post signed by the CEO announcing a license change from Apache 2.0 to Business Source License 1.1, a proprietary license. You can already find it in this PR, merged a couple days ago.

Akka 2.6 is on the open source Apache license, that is unchanged (its not possible for Lightbend to change an existing license). Its only the new Akka 2.7 which has the BSL license, so as long as you don't upgrade you are fine. See https://github.com/akka/akka/pull/31561.

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/