Kicking Butt on Concurrent Enterprise Application with Scala

Kicking butt on concurrent enterprise application with Scala By Azrul MADISA Freelance Java Developer azrulhasni@gmail.com

Plat du jour The concurrent enterprise The next billion users Asynchronous messaging Enter Scala Scala concurrency Scala actors Scala and Message Driven Beans

The ever concurrent enterprise Service A Service A Service A Service B Service B Service B Service C Service C Service C Service D Service D Service D Traditional Modern Web N.0 (large # of instances)

Commerce example Choose your things Choose from Choose from things in the things in the store store Pay Queue up Queue up (1 counter in (Many counters the shop) In the shop) Inventory Packaging Pay and delivery Pay Traditional Hypermarkets E-Commerce

Other sectors Telco Switch board → Exchanges → NGN Government Counter based → E-Government Finance Counter → ATM → E-Banking Others Millitary, logistics, media & content

The next billion users Sum of Bandwidth: Google, Twitter, Facebook etc. HPC (High performance Computing) Genomics, Animation *Prise (Enterprise) Cloud based, Saas, * http://blogs.sun.com/Gregp/entry/a_word_or_two_on

Don't mean to scare ya but... People are more network centric Every mobile device is a potential terminal to your services How many mobile devices are there? A couple of billion ? People are not the only ones accessing your services [Please hum the X-Files theme song in your head right now] => Computing demand grows faster than Moore's law Also known as the red shift

One word to rule them all ...

One word to rule them all ... i t y i l a b a l S c

What technology will allow this? Criteria Play well with current enterprise systems Play well on the JVM Fault tolerent Share-nothing philosophy Asynchronous messaging No side effect (Maybe functional) Easy to learn (tool support, language LAF) Performance – At least as good as current offerings Take advantage of multi-core tech.

Why asynchronous messaging important E-commerce example: Verify stock User choose Go to Start products checkout No Inform user End Stock exist? Take payment Yes End from user

Why asynchronous messaging important Verify stock Millions of items Kicker... need to lock an item while reserving it To avoid 2 person buying the same thing Lengthy => Clients will run away

Why asynchronous messaging important Simplified e- End commerce User choose Go to Take payment Start products checkout from user

Why asynchronous messaging important Simplified e- End commerce User choose Go to Take payment Start products checkout from user Fire another process Yes Packaging + End Shipment Verify stock Stock exist? Email to user – item would be End No a bit late

Long running transaction Short OLTP High volume processes We somewhat know how to do this High volume Long running processes ?

Long running transaction Client pay Package an item Ship to client's premise Client sign off

Long running transaction Client pay Package an item Reimburse 80% Back to client Exception! Ship to client's premise Ship back to Client cancel vendor's premise Client sign off

Enter Scala Created by Martin Odersky Made is Swiss (no, it's not a knife nor a kind of cheese) Run on Java JVM Java is king of the enterprise, running on JVM ensures adoption. Can use and inherit Java classes. Also runs on .Net CLR Object oriented and functional at the same time Statically typed with type inference Recently used by Twitter on the back-end ... replacing that other you-know-which language ;)

Why not the other JVM languages JRuby, Jython , <The dynamic language of the day> Duck typing? No thanks Clojure Interesting but syntax is too “lisp-y” - My personal opinion Plain old Java Are you kidding me? Image from: http://www.travelblog.org/Europe/Netherlands/North-Holland/Volendam/blog-385862.html

Scala concurrency: Immutable variables Immutable variables Variable that cannot change its value Useful in concurrent apps State cannot be inconsistent Easily declare variables as immutable The “val” keyword automatically makes variable immutable val movie = new Movie(“Wolverine”)

Scala concurrency: Immutable variables Can Java do this? Java does this on String For other object: Tedious since Java don't have operator overloading

Scala concurrency: Easy singleton Often times, we need one single object per application E.g. Some utility class to access the database Scala provide easy singleton: object MySingleton{ //singleton's body } The singleton's constructor is fully synchronized

Scala concurrency: Easy singleton Can we do this in Java Sure, but, again, it's tedious You have to create all the boilerplat code yourself Refer to the Gang Of Four book

Scala concurrency: Actors Scala has actors … and no, they're not as bad as Paris Hilton

Scala concurrency: Actors Actors Actors are objects Receive message asynchronously Reply with a Future Future = placeholder of future result Concurrency without threading Event-driven Unlike real-world actors, Scala actors are Cheap Totally ignored by politicians

Scala concurrency: Actors Event driven architecture Unlike threads, actors are event-driven Only become alive when there are messages to be processed. Execute on a thread pool With message passing, number of locks are low Great for multicore processors

Scala concurrency: Actors MainApp End User choose Go to Take payment Start products checkout from user Fire another process Yes Packaging + End Shipment Verify stock Stock exist? Email to user – item would be End Actor1 No a bit late

Scala concurrency: Actors case class MyMessage(myPaylod:String) //declare type of message object Actor1 extends Actor { def act = { loop { react { case MyMessage(“Continue e-commerce process”) => //Manage Stock verification, Packaging and Delivery here … //closing curly braces } object MainApp extends Application { //Do your business logic here, once you get to Payment ... Actor1.start Actor1 ! MyMessage(“Continue”) //send message to actor Actor1 }

Scala concurrency: Actors Can we do this in Java In plain old Java, thread can be used Thread can not be created in a Java EE container Have to use JMS OpenMQ ActiveMQ Message Driven Beans Message Driven Pojo with Spring

Scala concurrency: Reliability Short-comings of Scala messages They do not live in a transaction They cannot travel through a network There are projects to address this short coming Scala OTP (Equivalent to Erlang OTP) ActiveObject Another approach is to combine Scala and Java EE

Combining actors and message driven beans Scala Actors Message driven bean `

Combining actors and message driven beans Scala Actors Message driven bean ` Bridging agent acting like a “worm-hole” d Between the Scala world and MDB el ate re kr ! ! ta r T used uck d : S eing ek, NG e R NI is b t a g y WA alog e no an ou'r If y

Combining actors and message driven beans Scala world JMS world Request Actor javax.jms.MessageListener Queue WormholeActor MDB Scala object Spring's Message Driven Pojo Response Queue

Performance Shamelessly plucked from http://shootout.alioth.debian.org/u32q/benchmark.php?test=binarytrees&lang=all

Tools Netbeans, Eclipse and IDEA plugin

My wish list Scala actors working in XA Developing EJB 3.1 in Scala Seamlessly portable Scala apps to .Net Better IDE support Scala actors that can travel through a grid/cloud/network Pi-calculus Scala + SOA An international Scala conf. in Malaysia A magic flying talking pony err... car

Other interesting stuff Lift Scala web framework based on actors Scala books Testing ScalaTest

References The Scala official website scala-lang.org Ted Neward's Scala For Busy Java Developer Daniel Spiewak's Scala for Java Refugees Debasish Ghosh's Scala Actors 101 Various blogs, forums, people (too many to name … )

End note Scala is a sharp weapon to use in the coming “highly concurrent” age Hope to get you excited over Scala Play with it Test it Use it Twitt/blog about it Get something moving in Malaysia

Kicking Butt on Concurrent Enterprise Application with Scala

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