Dependency Injection with new Hosting Model

[shawndewet]

I have a Blazor server app into which I am registering Akka.Net as follows:

builder.Services.AddSingleton<SignalRConnectionList>();
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddAkka("AkkaESPoC", (configurationBuilder, provider) =>
{
    configurationBuilder
        .WithRemoting(hostName, port)
        .WithClustering(new ClusterOptions()
        { Roles = new[] { "Web" }, SeedNodes = seeds })
        .WithActors((system, registry) =>
        {
            var viewActorProps = system.ActorOf(Props.Create<QuestViewActor>(provider), "questview"); 
        });
});

Note how I am injecting the IServiceProvider into Actor props, and the actor's constructor creates a scope as follows:

public QuestViewActor(IServiceProvider serviceProvider)
        {
            _scope = serviceProvider.CreateScope();
... other code
        }

However, in the Receive method of the Actor, the services that are resolved are NOT the same services that are resolved elsewhere in the application:

Receive<QuestState>(async message =>
            {
                var _questHub = _scope.ServiceProvider.GetRequiredService<IHubContext<QuestHub>>();
                await _questHub.Clients.All.SendAsync("AddQuest", message.Data);

                var counter = _scope.ServiceProvider.GetRequiredService<SignalRConnectionList>();
                _log.Info($"Have {counter.Count} connections");
         });

I'm trying to resolve a SignalR IHubContext above, but the hub there has zero connections. So no views are receiving the messages.
I have confirmed that the scope inside the Actor Receive method is resolving different instances of services, in that the SignalRConnectionList is registered as a singleton, and elsewhere in my app, that .Count returns a value equal to the connections, BUT, in the above Actor Receive method, that count is zero.

What am I missing? How do get my actor to use the same DI Service Provider as the rest of my Blazor Application?

[bauersystems]

I may be wrong, as I am only new to Akka.net myself; however, I believe the issue may be to do with you attempting to pull a singleton via a scope. Instead of using the scope, try resolving the SignalRConnectionList directly from the Service Provider.

The other thing I did for mine was to not inject the IServiceProvider and use IDependencyResolver (from Akka.DependencyInjection) instead. Here is an example using IHttpClientFactory:
IDependencyResolver resolver = DependencyResolver.For(Context.System).Resolver; _httpClientFactory = resolver.GetService<IHttpClientFactory>();

If you need to pull in a scoped dependency, you can create a scope from the Dependency Resolver like the following:
IDependencyResolver resolver = DependencyResolver.For(Context.System).Resolver; resolver.CreateScope();
It seems to act the same as creating one through IServiceProvider, so I assume it is a wrapper under the surface (again, someone more experienced than me can confirm).
One thing to keep in mind when using a scope is to manage it in the PreStart & PostStart (as per the documentation https://getakka.net/articles/actors/dependency-injection.html#managing-lifecycle-dependencies-with-akkadependencyinjection)

[shawndewet]

As per your suggestion I've also configured a simple single-project Blazor app with Akka and SignalR, and am frustrated to say that it works! See here: https://github.com/shawndewet/BlazorWithAkkaSignalRSln.

[bauersystems]

I am not sure what is happening with your AkkaESPoC project, it is getting beyond my capabilities (as I mentioned previously, I am still learning too).

I did notice that you are attempting a lot of concepts at the same time (Clustering, Persistence, Pub/Sub, Protobuf). It might be worth using your BlazorWithAkkaSignalRSln project as a testing ground, adding new concepts to it one at a time to see how each concept works individually; then once you are finished you can have another look at AkkaESPoC and apply what you have learnt.

On a side note, for serialization I was running into trouble with the standard JSON serializer not being able to deal with my messages correctly, and Protobuf takes quite a bit to setup correctly (as you have seen), so I tried the new Hyperion one and it worked very well. To set it up with Akka.Hosting, it is as simple as .WithCustomSerializer("hyperion", new[] { typeof(object) }, system => new HyperionSerializer(system)).

I know that Aaron talks about ideally using Protobuf, however in the beginning it might be worth making the learning curve easier for yourself and just using a simpler serializer.

[shawndewet]

Thanks for your input @bauersystems.
I took a couple of hours yesterday and did exactly that...built a new PoC adding in concepts one at a time.
The core issue turned out to be frickin' nuget references!!!!

Because I was building the PoC based on the sharding-sqlserver sample I referred to earlier, I had the same Akka.Persistence.SqlServer.Hosting nuget reference in my Blazor project as that sample had in its web project.

So I replaced that with the references that were being used in my from-scratch BlazorWithAkkaSignalRSln project, and suddenly the issue was resolved! Yay.
So it must be that Akka.Persistence.SqlServer.Hosting is referencing earlier versions of the core Akka.Hosting dll's that do not yet do the DI stuff correctly.

But yay, the problem is solved! The actors in the Blazor project are now correctly doing SignalR!

[shawndewet]

Oh, and thanks for the tip about Hyperion @bauersystems ! Much much simpler!

[bauersystems]

I am glad to hear that you got it sorted out.

You might want to mark the discussion as answered ;-)

[shawndewet]

Thanks for your input @bauersystems.
I took a couple of hours yesterday and did exactly that...built a new PoC adding in concepts one at a time.
The core issue turned out to be frickin' nuget references!!!!

Because I was building the PoC based on the sharding-sqlserver sample I referred to earlier, I had the same Akka.Persistence.SqlServer.Hosting nuget reference in my Blazor project as that sample had in its web project.

So I replaced that with the references that were being used in my from-scratch BlazorWithAkkaSignalRSln project, and suddenly the issue was resolved! Yay.
So it must be that Akka.Persistence.SqlServer.Hosting is referencing earlier versions of the core Akka.Hosting dll's that do not yet do the DI stuff correctly.

But yay, the problem is solved! The actors in the Blazor project are now correctly doing SignalR!