Anatomy of a Reactive Application

Reactive Programming Enthusiasts Denver Meet-up Kick-Off

Mark Wilson

Demo Application

Scala

Akka

Play!

Intended to Illustrate some concepts of Reactive Programming, Introduce:

but the demo is mostly about Non-Blocking

Amdahl’s Law“… Therefore it is important that the entire solution is

asynchronous and non-blocking. ” - Reactive Manifesto

FuturesA Future is an object holding a value which

may become available at some point. !

• A Future is either completed or not completed • A completed Future is either:

• successful (value) • or failed (exception)

! import scala.concurrent.ExecutionContext.Implicits.global import scala.concurrent._

! val fs: Future[String] = Future { “a” + “b” } fs.onComplete { case Success(x) => println(x) case Failure(e) => throw e }

The Fish Store

1. Play GET and POST, non-blocking 2. Akka Actors processing a delivery

Start from the start a most simple web page

ActorFrom the book “Akka Concurrency”

by Derek Wyatt

Web Tier (Play)

Stateless: horizontally scalable

Aims to allow concurrency throughout the application

Fits with REST/ powerful javascript

An open source web application framework, written in Scala and Java, which follows the model–view–

controller architectural pattern.

AkkaUsing the Actor Model we raise the abstraction level and

provide a better platform to build correct, concurrent, and scalable applications. - akka docs

From the book “Akka

Concurrency” by Derek Wyatt

pipeTo import akka.pattern.pipe! val future: Future[Any] = someFunctionReturningFuture() future pipeTo sender // sends to sender as Future[Any]! // is roughly equivalent to! val mysender = sender // final def sender(): ActorRef future.onComplete { case Success(x) => mysender ! x case Failure(e) => mysender ! akka.actor.Status.Failure(e) }! // if sender doesn't handle Failure(e) it is logged as unhandled

Akka More..Configuration

Akka Test Kit

Akka Extensions

Akka Traits { Stash, ActorLogging }

TypedActor

Akka Events { EventBus, EventStream } - Pub/sub behavior

Akka Scheduler - sending a message to an actor on a schedule.

Supervision/Fault Tolerance { Resume, Restart, Stop, Escalate }

Data Flows - special lib for writing futures: flow { “hi” } onComplete println

Pipeline - sequential processing within an actor

Remote Actors - utilizing actors on remote machines (or clustered machines)

“It is better to fail in originality than to succeed in imitation.”

–Herman Melville

Up Next?!

March 2014

RPED Chunk-O-Thon OneCollective 3 minute presentations

Open participation

Topics span Reactive Applications

Examples:

Working examples / Shared learning exercise

Well formed problem/question for the group

Weird, funny or unexpected behavior

Realtime UI tricks

Other interesting stuff you come up with

Submissions must be available 1 week prior to meeting

There will be prizes!

March 2014