Building Reactive applications with Akka

Building Reactive applicationsusing Akka

Nilanjan Raychaudhuri@nraychaudhuri

Reactive Applications

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@nraychaudhuri

Essence of Reactive applications

Reactive Traits

Akka is enabler of Reactive applications


• Individual entities that can only communicate by passing messages

• Excellent for isolating mutable state and protecting it without locks

• Location transparency for remote and clustered topologies

• Supervision

• Well-suited for creating state machines

• Fault tolerance via Supervision

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Reference Architecture

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Play Server

Play Server

Play Server

Play Server

Web Tier (Play) Work Tier (Akka)

Akka Master Router

Akka Router Standby

Akka Worker

Akka Worker

Akka Worker

Akka Worker

Akka Worker

responsive event drivenscalableresilient

Message-driven

Reactive applications are architected based on loosely coupled design


Message-Driven• Loosely coupled architecture, easier to extend, maintain, evolve

• Asynchronous and non-blocking• Concurrent by design, immutable state• Lower latency and higher throughput

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“Clearly, the goal is to do these operations concurrently and non-blocking, so that entire blocks of seats or sections are not locked.

We’re able to find and allocate seats under load in less than 20ms without trying very hard to achieve it.”

Andrew Headrick, Platform Architect, Ticketfly

Introducing Actor Model

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A computational model that embodies:

✓ Processing

✓ Storage

✓ Communication

Supports 3 axioms—when an Actor receives a message it can:

1.Create new Actors

2.Send messages to Actors it knows

3.Designate how it should handle the next message it receives

Actor model

Thread pool

Actor modelActor model

Actor Actor

Akka actor -‐ Definition

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Akka actor -‐ Create

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Akka actor -‐ Send

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Elastic

Reactive applications scale up and down to meet demand

Elastic• Scalability and elasticity to embrace the Cloud

• Leverage all cores via asynchronous programming• Clustered servers support joining and leaving of nodes• More cost-efficient utilization of hardware

“Our traffic can increase by as much as 100x for 15 minutes each day. Until a couple of years ago, noon was a stressful time.

Nowadays, it’s usually a non-event.”

Eric Bowman, VP Architecture, Gilt Groupe

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FlightSearchActor

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FlightSearch Actor - I

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FlightSearch Actor - II

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FlightSearchActor

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SearchWorker - I

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SearchWorker - II

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ProviderProxyActor

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ProviderProxy - I

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ProviderProxy - II

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Flight search flow

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Let it crash

Reactive applications are architected to handle failure at all levels.

Resilient• Failure is embraced as a natural state in the app lifecycle

• Resilience is a first-class construct• Failure is detected, isolated, and managed• Applications self heal

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“The Typesafe Reactive Platform helps us maintain a very aggressive development and deployment cycle, all in a fail-forward manner.

It’s now the default choice for developing all new services.”

Peter Hausel, VP Engineering, Gawker Media

Failure?

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Think Vending Machine

Coffee MachineProgrammer

Inserts coins

Gets coffee

Add more coins


Coffee MachineProgrammer

Service Guy

Inserts coins

Gets coffee

Out of coffee beans

error

Adds more beans


Out of coffee beans errorWrong

The Right Way

ServiceClient

Supervisor

Request

Response

Validation Error

Application Error

Manages Failure

Supervision

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A

B

BarFoo

C

BE

A

C

system.actorOf(Props[Foo], “Foo”)

context.actorOf(Props[A], “A”)

Actor Topology

OneForOne

AllForOne


Isolate failure at all levels• Within one node

• Across many nodes (JVMs)

• Across many physical servers

• Across data centers

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Scale out

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Akka clustering


IoT

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Precision Farming

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Akka ClusterJournal

Q & Option[A]

@nraychaudhuri

Building Reactive applications with Akka

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