Http4s VS Play

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/

My major complain here is that, as far as being a web framework there is precious little information here about the framework. How does this framework scale with multiple requests? What concurrency strategy is it using (threads, processes, actors, etc?). Is this opinionated (it doesn't seem so but it also doesn't say it isn't either). How does this work with popular libraries x,y,z. The full docs have a little bit more information, but not a ton. But mostly there are some cute toy examples and "built in python" and thats about it.

Lets compare this with for example play https://www.playframework.com/ I know from this that it built on Akka, its stateless, aims for predictable resource consumption, has non-blocking io, etc. There is a ton of really important information on what does this web framework actually do that is really important when you are making a choice of a framework.

I have no idea how good this framework is, but besides a few toy examples, I can't see anything that makes me thing "wow this is great I need to use this".

A web application framework for Java/Scala: https://www.playframework.com/

Scala 3 migration isn't as simple as migrating other apps, you can track the work at https://github.com/playframework/playframework/issues/11260

And there are frameworks you can use to make development easier, like Play. And Java has plenty of choices for dependency injection frameworks.

However do note, Play should be perfectly usable as well, and it's still maintained by the community: https://github.com/playframework/playframework/issues/11649

In university I learned a bit of Java, so maybe I could use it professionally I guess?. There were many options to choose from. DropWizard, Spark, Play Framework. But the more documented one in the internet I found was Springboot, besides there were some courses in spanish and some friends that knew something about Springboot, so I give it a chance.

For a backend web server I use Play - https://www.playframework.com/ which I find to be the easiest one as a backend web server. For learning/using spark I found this course from coursera to be very useful. https://www.coursera.org/learn/scala-spark-big-data