Dr. Roland Kuhn Akka Tech Lead @rolandkuhn

Akka and AngularJS

Reactive Applications in Practice

Reactive  Applications

The Four Reactive Traits

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http://reactivemanifesto.org/

Akka !

A fully Reactive toolkit on the JVM

The Actor Model

• fully message-driven: an Actor can react by • sending messages to other Actors • creating Actors • denominating behavior for the next message

• Actors are effectively single-threaded • failures are contained and escalated within the

supervisor hierarchy • scaling up & out through location transparency

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Persistence Model: Event Sourcing

• based on storing change instead of updating state • persistent Actors generate events: • historic facts that do not change thereafter • storage is append-only log • current Actor state is updated by consuming events

• Actor can revisit the past by replaying events • events contain more business information than

current state snapshot

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Command Query Responsibility Segregation

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Client

write-!side

read-!side

Command Reply Query Reply

Events

Command Query Responsibility Segregation

• persistent Actors on write-side generate events • read-side independently consumes event streams • read model is fully decoupled from write model • queries are served from optimal storage: • SQL store • graph database • in-memory live view

• new read model can be generated on demand

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Spray / Akka HTTP !

An Actor-Based Web Toolkit

Web-Server made Simple

• HTTP requests and responses are Actor messages • powerful routing DSL turns Actor into Web-Server • not a web framework: • just expose Actors as web endpoints • nicely suited for RESTful APIs

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Important Disclaimer

• I know a lot about Akka, but … • I am not a web developer

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Gabbler: The Write-Side

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Gabbler Replayer

Journal

RouterLog

Input

POST

201

Gabbler: The Read-Side

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Gabbler Replayer

Journal

RouterLog

Input

GET

Replay

200

Gabbler: The Whole Thing

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Gabbler Replayer

Journal

RouterLog

Input

Further Information

• Code at https://github.com/hseeberger/gabbler • currently a pull request

• See also http://akka.io

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