ActorsAn introduction to

Johan Andrén johan.andren@mejsla.se | @apnylle

Akka with

Moores law

1971 today19902300

2,6 billions

1 million

Oh, No Problems!

Oh No, Problems!

• Race conditions

• Data corruption

• Deadlocks

• Thread contention

• Livelocks

• Priority Inversion

Concurrency is HARD• To write

• To test

• To debug

• To reason about

We need a better model!

A

B C

D

EF

ACTORSevent drivensystems with

Inbox

Behaviour

State

The only way to interact from

outside

• Single execution flow model

• No shared _mutable_ state

• Lightweight

• Loose coupling

• Easy to test

Actor A Actor B

Actor A Actor B

One way communication

Actor A Actor B

React, don’t wait

Actor AActor B1

Load balancing

Actor B2

router

Actor A Actor F (filter)

Pipe/Filter

Actor B

Actor A Actor B (chef)

ParallellizeActor C1

Actor C2

Actor C2

• No work, no thread used!

• Async - never actively wait

• Loose coupling

A

B C

D

EF

JVM

A

B C

D

EF

JVM 1 JVM 2

• Two actors on one core

• Two actors on separate cores

• Two actors on separate servers

The same same

Error handlingin Actor systems

• Leaking information between tiers

• Impossible to detect simultaneous errors

• The receiver does not know how to handle the errors!

Traditional model

Actor X

(parent)

Actor A

Actor Z

Error handling with Actors

Actor X

(parent)

Actor A

Actor Z

Error handling with Actors

Actor X

Actor A

Actor Z

Error handling with Actors

• Compartmentilization

• What goes back is explicit

• Separating error handling and business logic

• Can detect simultaneous errors

”Supervision”

• STM

• Remoting

• Clustring with no SPoF

• MQs integration

• Eventbus

Wait, there is more!

akka.ioWebsite:

But

Try it out! typesafe.comTypesafe Activator

• Simple but powerful model

• Lightweight and fast

• Loose coupling

• Resiliency

Recap

Johan Andrén johan.andren@mejsla.se | @apnylle

Questions?

Johan Andrén johan.andren@mejsla.se | @apnylle