# Introduction

THESE NOTES WILL BE UPDATED TO REFLECT FS2 1.x in 2019...HAD WAITED UNTIL THE API SETTLED DOWN

Reactive streams are computations organized to act on an infinite stream of data elements with bounded resource management. Most streaming libraries reflect the principles found in the [reactive streams manifesto](http://www.reactive-streams.org/). Reactive streams are designed to increase concurrency, manage back-pressure and improve expressiveness through composition.

There are many reactive streaming solutions including:

* [akka](http://akka.io) (cluster enabled)
* [scalaz-stream](https://github.com/scalaz/scalaz-stream)
* [haskell misc](http://www.haskellforall.com/2014/11/how-to-build-library-agnostic-streaming.html)

There are also solutions that run on clusters. Cluster-based libraries have different approaches to distributing computations. Cluster-based libraries include:

* [spark](https://spark.apache.org)
* [storm](https://storm.apache.org)
* [scalding](https://github.com/twitter/scalding)

This book contains notes for using fs2, formerly called scalaz-stream. These notes focus on practical uses of fs2 versus fs2's implementation details.

Note that fs2 is being rewritten from scalaz-stream and these notes have not been fully converte over yet. fs2 will not have dependencies on scalaz-stream or scalaz.


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