В данной лекции рассмотрена минимальная реализация акторной модели, включающая - отправку сообщений, - создание новых акторов и смену поведения для приема следующего сообщения. Исходный код реализации выложен на https://github.com/hwdtech/HWdTech.DS. Код на C#. При разработке использовались библиотеки: Autofac, NuUnit, Moq

1. Глава 5. Первая реализация 118

2. Концепция 119

3. IMessage 120
public interface IMessage
{
string Target
{
get;
}
}

4. MessageBus 121
public class MessageBus
{
public static void Send(IMessage message)
{…}
public static void Join(
string address,
Actor actor
)
{ … }
}

5. Actor 122
public abstract class Actor
{
public Actor(string address) { … }
public Actor() { … }
public void Become(Action<IMessage> handler)
{ … }
public void Receive(IMessage message) { … }
public abstract void Handle(IMessage message);
}

6. Фасад для IoC 123
public class DIContainer
{
IContainer container;
public T Resolve<T>()
{
return container.Resolve<T>();
}
}

7. Фасад для IoC 124
Файл: RouterImpl/IoCRegistration.cs
using Autofac;
namespace HWdTech.DS.Internals.Implementation
{
class RouterRegistrationModule : Module
{
protected override void Load(ContainerBuilder builder)
{
IRouter router = new RouterImpl();
builder.RegisterInstance(router).As<IRouter>();
}
}
}

8. Фасад для IoC 125
public class DIContainer
{
public DIContainer()
{
ContainerBuilder builder = new ContainerBuilder();
Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
builder.RegisterAssemblyModules(assemblies);
this.container = builder.Build();
AppDomain.CurrentDomain.AssemblyLoad += AssemblyLoadEventHandler;
}
void AssemblyLoadEventHandler(object sender, AssemblyLoadEventArgs args)
{
LoadAssembly(args.LoadedAssembly);
}
LoadAssembly(Assembly assembly)
{
ContainerBuilder builder = new ContainerBuilder();
builder.RegisterAssemblyModules(assembly);
builder.Update(container);
}
}

9. Реализация MessageBus.Join 126
static IRouter router;
public static void Join(string address, Actor actor)
{
if (null == router)
{
router = Singleton<DIContainer>.Instance.Resolve<IRouter>();
}
router.RegisterOrReplace(address, actor.Receive);
}

10. Реализация MessageBus.Send 127
static IThreadPool threadPool;
public static void Send(IMessage message)
{
if (null == threadPool) {
threadPool = Singleton<DIContainer>.Instance.Resolve<IThreadPool>();
}
threadPool.StartTask(HandleMessage, message);
}
static void HandleMessage(object o)
{
IMessage message = (IMessage) o;
if (null == router) {
router = Singleton<DIContainer>.Instance.Resolve<IRouter>();
}
router.Send(message);
}

11. Ping-Pong Test 128
[Test]
public void PingPongTest()
{
ThreadPoolImpl threadPool = new ThreadPoolImpl();
RouterImpl router = new RouterImpl();
Mock<IMessage> pingMessage = repository.Create<IMessage>();
pingMessage.SetupGet(m => m.Target).Returns("ping");
Actor pongActor = new PongActor(pingMessage.Object);
Mock<IMessage> pongMessage = repository.Create<IMessage>();
pongMessage.SetupGet(m => m.Target).Returns("pong");
ManualResetEvent waitSignal = new ManualResetEvent(false);
PingActor pingActor = new PingActor(pongMessage.Object, waitSignal);
Assert.True(waitSignal.WaitOne(1000));
pingActor.Verify();
}

12. Ping-Pong Test: Ping Actor 129
class PingActor : Actor{
int gotMessages;
IMessage pongMessage;
ManualResetEvent signal;
const int numberOfResponsesShoulgGet = 5;
public PingActor(IMessage pongMessage, ManualResetEvent signal) : base("ping") {
this.signal = signal;
this.pongMessage = pongMessage;
MessageBus.Send(pongMessage);
}
public override void Handle(IMessage message) {
++gotMessages;
if (numberOfResponsesShoulgGet > gotMessages) {
MessageBus.Send(pongMessage);
}
else { signal.Set(); }
}
public void Verify() {
Assert.AreEqual(numberOfResponsesShoulgGet, gotMessages);
}
}

13. Ping-Pong Test: Pong Actor 130
class PongActor : Actor
{
IMessage pingMessage;
public PongActor(IMessage pingMessage)
: base("pong")
{
this.pingMessage = pingMessage;
}
public override void Handle(IMessage message)
{
MessageBus.Send(pingMessage);
}
}

14. Фасад для ThreadPool 131
public interface IThreadPool
{
void StartTask(Action<object> task, object arg);
}
public class ThreadPoolImpl : IThreadPool
{
public void StartTask(Action<object> action, object args = null)
{
System.Threading.ThreadPool.QueueUserWorkItem(new
System.Threading.WaitCallback(action), args);
}
}

15. Пример теста для ThreadPool 132
[Test]
public void ThreadPoolShouldRunTasksWithArgument()
{
System.Threading.ManualResetEvent canContinue = new
System.Threading.ManualResetEvent(false);
ThreadPoolImpl pool = new ThreadPoolImpl();
object o = new object();
bool gotArgument = false;
pool.StartTask((obj) => {
gotArgument = object.ReferenceEquals(obj, o);
canContinue.Set();
}, o);
Assert.True(canContinue.WaitOne(1000));
Assert.True(gotArgument);
}

16. Фасад для роутера 133
public interface IRouter
{
void Send(IMessage message);
IRouter RegisterOrReplace(string channel, Action<IMessage> handler);
}

17. Фасад для роутера 134
public class RouterImpl: IRouter {
public RouterImpl() {
routerImpl = new ConcurrentDictionary<string, Action<IMessage>>();
}
public void Send(IMessage message)
{
Action<IMessage> handler;
if (routerImpl.TryGetValue(message.Target, out handler)) {
handler(message);
}
else { //ToDo: адресат неизвестен - надо разрешить с помощью внешнего сервиса.
}
}
public IRouter RegisterOrReplace(string channel, Action<IMessage> handler)
{
routerImpl.AddOrUpdate(channel, handler, (key, oldValue) => { return handler; });
return this;
}
ConcurrentDictionary<string, Action<IMessage>> routerImpl;
}