Scala in Practice · Scala & Java For All You Know, It's Just a Java Library ... Reactive Systems...

Scala in Practice

A pragmatic view on programming language adoption

Lutz Huehnken - Solutions Architect, Typesafe, Inc. @lutzhuehnken

I.Should a Pragmatist Care About languages? II.The Case For Scala III.Scala in The Real World IV.Scala Adoption Done Right

Jazoon - Scala in Practice 5

Telling The Computer What To Do..

A programming language is for telling the computer what to do

Any Turing-complete language can do that


.. vs. Building A Model Of The World

The World is

• People and things (objects) interacting which each other?

• Described by laws of science and mathematics?

• Based on logic?


Ludwig Wittgenstein (1889 - 1951)

The limits of my language are the limits of my mind.

All I know is what I have words for.

Image from Wikipedia


A. Expressiveness

OOP

Functional Programming

Model

Logic Programming


B. Productivity

Managed Runtime /

Garbage Collection

> No Garbage Collection

Strongly Typed &

Static Type-Checking

> Weakly Typed or

Dynamic Type-Checking


C. Community

https://twitter.com/kilaulena/status/463317989648248832


Pragmatic Language Choice

Expressiveness

Productivity

Language

Communities


Scala unifies OO and FP

http://www.scala-lang.org


Scala leverages the JVM Eco System


Scala & Java

For All You Know, It's Just a Java Library

The customer asks "Where's the Scala part?" I answer "It's in this JAR file." He goes "But, your program is written in Scala, but I looked at the byte-code and it's just Java." I answer "It's Scala... but it compiles down to Java byte-code and it runs in a Java debugger and you can't tell the difference." "You're right," he says.

So, to this customer's JVM, the Scala and Lift code looks, smells and tastes just like Java code. If I renamed the scala-library.jar file to apache-closures.jar, nobody would know the difference... at all.

http://blog.goodstuff.im/just_another_java_library


Communities: Java

Internet Tech in Enterprises

Mobile

Java

Android

Java EE

Spring


Communities: Python

Scientific Computing Data Science

Python

iPython Notebook

NumPy

SciPy


Communities: Scala

Reactive Systems

Big Data

Scala

Spark

Akka

ScalaZ

Functional Programming

Typelevel (shapeless,

cats, ..)


The Case For Scala

Expressiveness

Productivity

Scala

OO

Big Data!

CommunitiesReactive!

Java Eco System and Tooling

FP

Jazoon - Scala in Practice


Apache Kafka

• Developed at LinkedIn

• Typical use-case: central publish-subscribe log for integrating data between applications, stream processing, data ingestion (Spark, Hadoop)


Apache Kafka

• 3x Intel Xeon 2.5 GHz processor (6 cores)

• Three producers, 3x async replication • 2,024,032 records/sec

• Three Consumers • 2,615,968 records/sec


It’s just too big right now to not mention it..


Twitter - may be not the role model for your company

• Early adaptor, but highly customized • E.g. Twitter „Futures“

• Twitter-Stack (Finagle etc.) • Build system (Pants)

• But

• Performance / scaling problem solved • Scala going strong at Twitter for 6 years now • And with some impact - „Server as a Function“


Soundcloud


Soundcloud - a bit of history

It was a phase of high experimentation, and instead of defining which languages or runtimes these teams should use, we had the rule of thumb write it in whatever you feel confident enough putting in production and being on-call for.This led to a Cambrian Explosion of languages, runtimes and skills. We had systems being developed in everything from Perl to Julia, including Haskell, Erlang, and node.js.[..]We have used Finagle for HTTP, Thrift, memcached, Redis, and MySQL. Every request to the SoundCloud platform is very likely hitting at least one of our Finagle-powered microservices, and the performance we have from these is quite amazing.

http://en.wikipedia.org/wiki/Cambrian_explosion


Morgan Stanley

Rumors

• Adoption is language - driven

• Scala because of • Functional Programming • Flexibility (DSLs, Macros..)


UniCredit

Rumors

• Akka & externally driven

• Very skeptical of Scala • Need for some scalable, real time event processing • SI chose Akka, Scala • Delivered under time & budget • Scala it is


Galeria Kaufhof

• Driven by „epiphany“: We need to be a tech company

• From standard software to build-your-own • Culture change - pure retailer to tech focus


Galeria Kaufhof

JUMP!

http://www.inoio.de/blog/2014/09/20/technologie-sprung-bei-galeria-kaufhof/


Galeria Kaufhof


Zalando

• Magento -> Java -> Scala • Actually polyglot, autonomous teams • But must be on tech radar • Polyglot is great, but maybe not for everyone


Renault R-Link

• Driven by Akka

• Build by AtoS


Scala Caveats

For All You Know, It's Just a Java Library.. .. but it’s not!

That may be true at runtime - but certainly not in development.

Josh Suereth:This is an important point. Scala is not just a “Java++”. There’s a lot of depth to pull out of the language, and lots you can learn. It doesn’t take a lot to start, but it can be intimidating how much is out there. You need to be prepared for it to take some time to learn things


Scala Caveats

sbt

But once you get the hang of it.. define your Scala build in Scala.

It’s actually a great tool


Scala Caveats

Parts of the community

But everyone I interacted with in the Scala community was super

friendly and helpful.

Disclaimer: Maybe Tony Morris is, too - I don’t know him and never met him.

These „headlines“ are about all I know about him.


Scala Caveats

• There is no „Scala EE“. Yet.

• But patterns are evolving.


Scala Caveats

• The power to split teams

• Goes hand in hand with „We do, because we

can“

• Comp. Design Patterns


Scala Caveats

• We can ≠ we should

• Coding guidelines

• See Twitter, Kafka, Spark..


So do what?

• Introduce Scala!

•What is your driver? Focus on that.

•Give team time to learn, get trainings

•Establish coding guidelines

•Address and avoid split proactively

•There will be along on the road

•But it’s worth it!

Thank You

Lutz Huehnken - Solutions Architect, Typesafe, Inc. @lutzhuehnken

Scala in Practice · Scala & Java For All You Know, It's Just a Java Library ... Reactive Systems...

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