Actor Model in .NET:Akka.NET vs Microsoft Orleans

for the curious

William TullochLead Consultant – Readify@wtulloch

PreambleConcurrency and distributed applications

What is the Actor Model?

The Model of Actor Model

A way of reasoning about concurrent computation

What is the Actor Model

A way of reasoning about concurrent computationIs inherently concurrent

The Model of Actor Model

Is a conceptual model for reasoning about concurrent computationIs inherently concurrentManages concurrency through message passing

The Model of Actor Model

Is a conceptual model for reasoning about concurrent computation

Adopts the philosophy that everything is an actor

Is inherently concurrentManages concurrency through message passing

What is an Actor? Lightweight

Never shares state

Communicates through asynchronous messagesHas a mailbox to buffer messages

Processes one message at a time

Is a single-thread object

An Actor Can not exist on its own

Microsoft Orleans&

Akka.NET

The overview

Akka.NET

• A port of Java/Scala Akka

• Open source

• Task Parallel Library

• Reactive methodology• Can be run within an

application, on-prem or in the cloud(?)

The overview

Orleans

• Started by Microsoft Research

• Open source

• Task Parallel Library

• Reactive methodology

• Cloud-native

Akka.NET

• A port of Java/Scala Akka

• Open source

• Task Parallel Library

• Reactive methodology• Can be run within an

application, on-prem or in the cloud(?)

Orleans versus Akka.NET

Hosting Actors

Image from Halo Orleans at build 2104

Orleans - Silo Akka - ActorSystem

Hosting Actors

Image from Halo Orleans at build 2104

Orleans - Silo Akka - ActorSystem

Actors versus Grains

Orleans: An Actor is Grain

Grain instances always exist virtually

Orleans: An Actor is Grain

Grain instances always exist virtuallyAre created on demand

Orleans: An Actor is Grain

Grain instances always exist virtuallyAre created on demand

Are location transparent

Orleans: An Actor is Grain

Grain instances always exist virtuallyAre created on demand

Are location transparent

Every grain must have an Id

Akka.NET: An Actor is Actor

Must be explicitly created and stopped

Akka.NET: An Actor is Actor

Must be explicitly created and stoppedAre created in the context of their parent

Akka.NET: An Actor is Actor

Must be explicitly created and stoppedAre created in the context of their parentExposes a set of life-cycle hooks

Akka.NET: An Actor is Actor

Must be explicitly created and stoppedAre created in the context of their parentExposes a set of life-cycle hooks Are location transparentakka.tcp://Demo@127.0.0.1:12345/user/HelloWorld/$c

Creating grains and actors

Creating a grain

Orleans – creating a grain

• In Visual Studio create two projects•One for your grain interfaces•One for your grain implementations

• In both projects install the NuGet package Microsoft.Orleans.OrleansCodeGenerator.build

Create a Grain interface

public interface IHelloWorld : IGrainWithIntegerKey{ Task Greeting(string name);

Task<string> ReturnGreeting(string name);}

Must implement one of the following:• IGrainWithIntegerKey• IGrainWithGuidKey• IGrainWithStringKey• IGrainWithIntegerCompou

ndKey• IGrainWithGuidCompound

Key

Create an implementation of the interface

public class HelloWorldGrain : Grain, IHelloWorld{ public Task Greeting(string name) { Console.WriteLine($"Hi {name} from Orleans"); return TaskDone.Done; } public Task<string> ReturnGreeting(string name) { return Task.FromResult($"Hi {name} from Orleans"); }}

Interacting with Grains

static async Task SendMessage(User user ){ var helloWorld = GrainClient.GrainFactory.GetGrain<IHelloWorld>(0); var response = await helloWorld.Greeting(user); WriteLine(response);}

Creating an Actor

Akka.Net – creating an actor

• In Visual Studio:• Create a new class library • Create a console application

• Import the core Akka.NET Nuget package: Akka

Create message

public class HelloUserMessage{ public User User { get; } public HelloUserMessage(User user) { User = user; }}

Create an actorpublic class HelloWorldActor : ReceiveActor{ private TimeSpan _waitPeriod; public HelloWorldActor(TimeSpan waitPeriod) { _waitPeriod = waitPeriod;

Receive<HelloUserMessage>(m => { var user = m.User; Thread.Sleep(_waitPeriod); WriteLine($"Hi {user.Id} {user.FirstName} nice to meet you [on thread "); }); Receive<DataCompleted>(m => WriteLine("Data is completed"));}

Using the actor

var system = ActorSystem.Create("demo")

var helloWorld = system.ActorOf(Props.Create(() => new HelloWorldActor()));

helloWorld.Tell(new HelloUserMessage(new User());

await system.Terminate();

Demo Hello World

Messages and Serialisation

Messages and Serialisation

public class UserMessage { public string FirstName { get;} public string LastName { get;} public UserMessage(string firstName, string lastName) { FirstName = firstName; LastName = lastName; }}

Messages and serialisation

Task<string> Greeting(string firstName, string lastName);

Task<Immutable<byte[]>> ProcessRequest(Immutable<byte[]> request);

Messages and Serialisation

[Immutable] public class User { public string FirstName { get;} public string LastName { get;}}

Bits and Pieces

“let it crash” and exception handlingPersisting stateChanging behaviourGrains for everyoneRouting in Akka.NETClustering in Akka.NET

Summing up

Resources

Akka.NETAkka.NET home: http://getakka.net/Bootcamp: https://github.com/petabridge/akka-bootcamp

OrleansOrleans Home: http://dotnet.github.io/orleans/Halo-Orleans: https://channel9.msdn.com/Events/Build/2014/3-

641

Comparing Akka.NET and Orleans: https://github.com/akka/akka-meta/blob/master/ComparisonWithOrleans.md