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How to: Run and use virtual actors in the .NET SDK
The Dapr actor package allows you to interact with Dapr virtual actors from a .NET application. In this guide, you learn how to:
- Create an Actor (
MyActor
). - Invoke its methods on the client application.
MyActor --- MyActor.Interfaces
|
+- MyActorService
|
+- MyActorClient
The interface project (\MyActor\MyActor.Interfaces)
This project contains the interface definition for the actor. Actor interfaces can be defined in any project with any name. The interface defines the actor contract shared by:
- The actor implementation
- The clients calling the actor
Because client projects may depend on it, it’s better to define it in an assembly separate from the actor implementation.
The actor service project (\MyActor\MyActorService)
This project implements the ASP.Net Core web service that hosts the actor. It contains the implementation of the actor, MyActor.cs
. An actor implementation is a class that:
- Derives from the base type Actor
- Implements the interfaces defined in the
MyActor.Interfaces
project.
An actor class must also implement a constructor that accepts an ActorService
instance and an ActorId
, and passes them to the base Actor class.
The actor client project (\MyActor\MyActorClient)
This project contains the implementation of the actor client which calls MyActor’s method defined in Actor Interfaces.
Prerequisites
- Dapr CLI installed.
- Initialized Dapr environment.
- .NET Core 3.1 or .NET 6+ installed. Dapr .NET SDK uses ASP.NET Core.
Step 0: Prepare
Since we’ll be creating 3 projects, choose an empty directory to start from, and open it in your terminal of choice.
Step 1: Create actor interfaces
Actor interface defines the actor contract that is shared by the actor implementation and the clients calling the actor.
Actor interface is defined with the below requirements:
- Actor interface must inherit
Dapr.Actors.IActor
interface - The return type of Actor method must be
Task
orTask<object>
- Actor method can have one argument at a maximum
Create interface project and add dependencies
# Create Actor Interfaces
dotnet new classlib -o MyActor.Interfaces
cd MyActor.Interfaces
# Add Dapr.Actors nuget package. Please use the latest package version from nuget.org
dotnet add package Dapr.Actors
cd ..
Implement IMyActor interface
Define IMyActor
interface and MyData
data object. Paste the following code into MyActor.cs
in the MyActor.Interfaces
project.
using Dapr.Actors;
using Dapr.Actors.Runtime;
using System.Threading.Tasks;
namespace MyActor.Interfaces
{
public interface IMyActor : IActor
{
Task<string> SetDataAsync(MyData data);
Task<MyData> GetDataAsync();
Task RegisterReminder();
Task UnregisterReminder();
Task<IActorReminder> GetReminder();
Task RegisterTimer();
Task UnregisterTimer();
}
public class MyData
{
public string PropertyA { get; set; }
public string PropertyB { get; set; }
public override string ToString()
{
var propAValue = this.PropertyA == null ? "null" : this.PropertyA;
var propBValue = this.PropertyB == null ? "null" : this.PropertyB;
return $"PropertyA: {propAValue}, PropertyB: {propBValue}";
}
}
}
Step 2: Create actor service
Dapr uses ASP.NET web service to host Actor service. This section will implement IMyActor
actor interface and register Actor to Dapr Runtime.
Create actor service project and add dependencies
# Create ASP.Net Web service to host Dapr actor
dotnet new web -o MyActorService
cd MyActorService
# Add Dapr.Actors.AspNetCore nuget package. Please use the latest package version from nuget.org
dotnet add package Dapr.Actors.AspNetCore
# Add Actor Interface reference
dotnet add reference ../MyActor.Interfaces/MyActor.Interfaces.csproj
cd ..
Add actor implementation
Implement IMyActor interface and derive from Dapr.Actors.Actor
class. Following example shows how to use Actor Reminders as well. For Actors to use Reminders, it must derive from IRemindable. If you don’t intend to use Reminder feature, you can skip implementing IRemindable and reminder specific methods which are shown in the code below.
Paste the following code into MyActor.cs
in the MyActorService
project:
using Dapr.Actors;
using Dapr.Actors.Runtime;
using MyActor.Interfaces;
using System;
using System.Threading.Tasks;
namespace MyActorService
{
internal class MyActor : Actor, IMyActor, IRemindable
{
// The constructor must accept ActorHost as a parameter, and can also accept additional
// parameters that will be retrieved from the dependency injection container
//
/// <summary>
/// Initializes a new instance of MyActor
/// </summary>
/// <param name="host">The Dapr.Actors.Runtime.ActorHost that will host this actor instance.</param>
public MyActor(ActorHost host)
: base(host)
{
}
/// <summary>
/// This method is called whenever an actor is activated.
/// An actor is activated the first time any of its methods are invoked.
/// </summary>
protected override Task OnActivateAsync()
{
// Provides opportunity to perform some optional setup.
Console.WriteLine($"Activating actor id: {this.Id}");
return Task.CompletedTask;
}
/// <summary>
/// This method is called whenever an actor is deactivated after a period of inactivity.
/// </summary>
protected override Task OnDeactivateAsync()
{
// Provides Opporunity to perform optional cleanup.
Console.WriteLine($"Deactivating actor id: {this.Id}");
return Task.CompletedTask;
}
/// <summary>
/// Set MyData into actor's private state store
/// </summary>
/// <param name="data">the user-defined MyData which will be stored into state store as "my_data" state</param>
public async Task<string> SetDataAsync(MyData data)
{
// Data is saved to configured state store implicitly after each method execution by Actor's runtime.
// Data can also be saved explicitly by calling this.StateManager.SaveStateAsync();
// State to be saved must be DataContract serializable.
await this.StateManager.SetStateAsync<MyData>(
"my_data", // state name
data); // data saved for the named state "my_data"
return "Success";
}
/// <summary>
/// Get MyData from actor's private state store
/// </summary>
/// <return>the user-defined MyData which is stored into state store as "my_data" state</return>
public Task<MyData> GetDataAsync()
{
// Gets state from the state store.
return this.StateManager.GetStateAsync<MyData>("my_data");
}
/// <summary>
/// Register MyReminder reminder with the actor
/// </summary>
public async Task RegisterReminder()
{
await this.RegisterReminderAsync(
"MyReminder", // The name of the reminder
null, // User state passed to IRemindable.ReceiveReminderAsync()
TimeSpan.FromSeconds(5), // Time to delay before invoking the reminder for the first time
TimeSpan.FromSeconds(5)); // Time interval between reminder invocations after the first invocation
}
/// <summary>
/// Get MyReminder reminder details with the actor
/// </summary>
public async Task<IActorReminder> GetReminder()
{
await this.GetReminderAsync("MyReminder");
}
/// <summary>
/// Unregister MyReminder reminder with the actor
/// </summary>
public Task UnregisterReminder()
{
Console.WriteLine("Unregistering MyReminder...");
return this.UnregisterReminderAsync("MyReminder");
}
// <summary>
// Implement IRemindeable.ReceiveReminderAsync() which is call back invoked when an actor reminder is triggered.
// </summary>
public Task ReceiveReminderAsync(string reminderName, byte[] state, TimeSpan dueTime, TimeSpan period)
{
Console.WriteLine("ReceiveReminderAsync is called!");
return Task.CompletedTask;
}
/// <summary>
/// Register MyTimer timer with the actor
/// </summary>
public Task RegisterTimer()
{
return this.RegisterTimerAsync(
"MyTimer", // The name of the timer
nameof(this.OnTimerCallBack), // Timer callback
null, // User state passed to OnTimerCallback()
TimeSpan.FromSeconds(5), // Time to delay before the async callback is first invoked
TimeSpan.FromSeconds(5)); // Time interval between invocations of the async callback
}
/// <summary>
/// Unregister MyTimer timer with the actor
/// </summary>
public Task UnregisterTimer()
{
Console.WriteLine("Unregistering MyTimer...");
return this.UnregisterTimerAsync("MyTimer");
}
/// <summary>
/// Timer callback once timer is expired
/// </summary>
private Task OnTimerCallBack(byte[] data)
{
Console.WriteLine("OnTimerCallBack is called!");
return Task.CompletedTask;
}
}
}
Register actor runtime with ASP.NET Core startup
The Actor runtime is configured through ASP.NET Core Startup.cs
.
The runtime uses the ASP.NET Core dependency injection system to register actor types and essential services. This integration is provided through the AddActors(...)
method call in ConfigureServices(...)
. Use the delegate passed to AddActors(...)
to register actor types and configure actor runtime settings. You can register additional types for dependency injection inside ConfigureServices(...)
. These will be available to be injected into the constructors of your Actor types.
Actors are implemented via HTTP calls with the Dapr runtime. This functionality is part of the application’s HTTP processing pipeline and is registered inside UseEndpoints(...)
inside Configure(...)
.
Paste the following code into Startup.cs
in the MyActorService
project:
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
namespace MyActorService
{
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.AddActors(options =>
{
// Register actor types and configure actor settings
options.Actors.RegisterActor<MyActor>();
});
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseRouting();
app.UseEndpoints(endpoints =>
{
// Register actors handlers that interface with the Dapr runtime.
endpoints.MapActorsHandlers();
});
}
}
}
Step 3: Add a client
Create a simple console app to call the actor service. Dapr SDK provides Actor Proxy client to invoke actor methods defined in Actor Interface.
Create actor client project and add dependencies
# Create Actor's Client
dotnet new console -o MyActorClient
cd MyActorClient
# Add Dapr.Actors nuget package. Please use the latest package version from nuget.org
dotnet add package Dapr.Actors
# Add Actor Interface reference
dotnet add reference ../MyActor.Interfaces/MyActor.Interfaces.csproj
cd ..
Invoke actor methods with strongly-typed client
You can use ActorProxy.Create<IMyActor>(..)
to create a strongly-typed client and invoke methods on the actor.
Paste the following code into Program.cs
in the MyActorClient
project:
using System;
using System.Threading.Tasks;
using Dapr.Actors;
using Dapr.Actors.Client;
using MyActor.Interfaces;
namespace MyActorClient
{
class Program
{
static async Task MainAsync(string[] args)
{
Console.WriteLine("Startup up...");
// Registered Actor Type in Actor Service
var actorType = "MyActor";
// An ActorId uniquely identifies an actor instance
// If the actor matching this id does not exist, it will be created
var actorId = new ActorId("1");
// Create the local proxy by using the same interface that the service implements.
//
// You need to provide the type and id so the actor can be located.
var proxy = ActorProxy.Create<IMyActor>(actorId, actorType);
// Now you can use the actor interface to call the actor's methods.
Console.WriteLine($"Calling SetDataAsync on {actorType}:{actorId}...");
var response = await proxy.SetDataAsync(new MyData()
{
PropertyA = "ValueA",
PropertyB = "ValueB",
});
Console.WriteLine($"Got response: {response}");
Console.WriteLine($"Calling GetDataAsync on {actorType}:{actorId}...");
var savedData = await proxy.GetDataAsync();
Console.WriteLine($"Got response: {savedData}");
}
}
}
Running the code
The projects that you’ve created can now to test the sample.
-
Run MyActorService
Since
MyActorService
is hosting actors, it needs to be run with the Dapr CLI.cd MyActorService dapr run --app-id myapp --app-port 5000 --dapr-http-port 3500 -- dotnet run
You will see commandline output from both
daprd
andMyActorService
in this terminal. You should see something like the following, which indicates that the application started successfully.... ℹ️ Updating metadata for app command: dotnet run ✅ You're up and running! Both Dapr and your app logs will appear here. == APP == info: Microsoft.Hosting.Lifetime[0] == APP == Now listening on: https://localhost:5001 == APP == info: Microsoft.Hosting.Lifetime[0] == APP == Now listening on: http://localhost:5000 == APP == info: Microsoft.Hosting.Lifetime[0] == APP == Application started. Press Ctrl+C to shut down. == APP == info: Microsoft.Hosting.Lifetime[0] == APP == Hosting environment: Development == APP == info: Microsoft.Hosting.Lifetime[0] == APP == Content root path: /Users/ryan/actortest/MyActorService
-
Run MyActorClient
MyActorClient
is acting as the client, and it can be run normally withdotnet run
.Open a new terminal an navigate to the
MyActorClient
directory. Then run the project with:dotnet run
You should see commandline output like:
Startup up... Calling SetDataAsync on MyActor:1... Got response: Success Calling GetDataAsync on MyActor:1... Got response: PropertyA: ValueA, PropertyB: ValueB
💡 This sample relies on a few assumptions. The default listening port for an ASP.NET Core web project is 5000, which is being passed to
dapr run
as--app-port 5000
. The default HTTP port for the Dapr sidecar is 3500. We’re telling the sidecar forMyActorService
to use 3500 so thatMyActorClient
can rely on the default value.
Now you have successfully created an actor service and client. See the related links section to learn more.
Related links
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