Akka.NET: Concurrency Without the Pain (Intro to the Actor Model)

@petabridge Petabridge.com

Concurrency Without the Pain:An Intro to the Actor Model

Andrew Skotzko Co-‐founder — Petabridge



Why should we care about concurrency?


1970 -‐ 2005






TANSTAAFL“There ain’t no such thing as a free lunch.” —R. A. Heinlein, The Moon Is a Harsh Mistress



WTF are you talking about?


Concurrency.

Time to make friends.


So what’s the problem?


How to Write Multithreaded Code

Shared StateProgramming

Make classes andfunctions

Find areas where youcan do multiple things

at once

Queue work onto a newthread or thread pool

Use synchronizationmechanisms to

protected sharedmemory (what?!?!)

Finish work on onethread

Consume that work onanother


Shared State Programming Sucks (Illustrated)

Shared StateProgramming

Problems

Synchronizing shared state == pitof doom

Deadlocks

Livelocks

Unsafe state

Coordinating work between threads

Debugging multi-threaded code:not for the faint of heart

Hey, that third party code you'reusing - is it thread safe?

Writing thread-safe code is hard


Random?

• .NET 4.0: TPL (2010) • .NET 4.5: async/await (2012)


Is there a better way? THERE MUST BE!THERE. MUST. BE. A. BETTER. WAY!


Warning! Mind Blowingly Different

Programming Style Ahead!


Warning! Mind Blowingly Different Programming Style Ahead!


The Actor Model


What is the actor model?


Everything is an actor.




3 Core Abilities

1. Send messages 2. Create other actors 3. Change behavior


Messages


Actors work by passing each other messages


Message passing in action

Send "Hello" to "/user/actor1"

Received "Hello" from"/user/actor2"(do some work)

Send "Sup homedawg" to "/user/actor2"


BUZZWORD BINGO!


Example Akka.NET Message


Actors send messages to addresses

akka.tcp: / /MySystem@localhost:9001/user/actorName1

Protocol

ActorSystem

Address

Path

All parts form an "ActorPath"


Actor addresses have location transparency


Which means…




Magical scaling sauce! (more on that later)


ReactiveManifesto.org


What is Akka.NET?


Obligatory logos to impress you


This is an actor


These are messages


Actors run on threads


Actors are lazy


Process messages one at a time


The circle of life


Actor lifecycle


Actor lifecycle



Hierarchies


Supervision


Switchable Behavior


Magic Scaling Sauce!!!


(High Availability)


We Can Deploy Actors and Send Messages Anywhere

Nice hair!

Did you hear?My hairrocks!

Dude, don'tencourage

him.


Scaling Out

• Actors can be deployed anywhere

• Special "Router" actors distribute work

• Actors can be easily restarted and redeployed


And Can Form Highly Available Systems

Ready forwork!


http://LearnAkka.net


Have questions? Ask us!

[email protected] Intro: http://learnakka.net


Hierarchies pt. deux


Error Kernel

Technology

Akka.NET: Concurrency Without the Pain (Intro to the Actor Model)