Add a self hosted SignalR server to a .Net Core Worker Service - asp.net-core-signalr

Question

I'm trying to extend a .NET Core Worker Service (<Project Sdk="Microsoft.NET.Sdk.Worker">) with SignalR (self hosted web app).
All the examples/tutorials/docs I have found are based on web applications, so they don't fit my case.
This is what I've done until now:
MyService Program.cs:
public class Program
{
public static void Main(string[] args)
{
CreateHostBuilder(args).Build().Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.UseWindowsService()
.ConfigureServices((hostContext, services) =>
{
services.AddHostedService<Worker>();
DependencyBuilder.Build(hostContext, services); // inject the stuff I need in my service
// create a SignalR Web host
SignalRWebHostCreator.CreateHost(services, "http://localhost:8090", (endpoints) => {
endpoints.MapHub<MyHub>("/result");
});
});
}
and the class I want to use to "extend" the servie with a SignalR server application.
public class SignalRWebHostCreator
{
public static void CreateHost(IServiceCollection services, string serviceUrl, Action<IEndpointRouteBuilder> mapHubs)
{
services.AddSignalR(); // is it ok here ?
WebHost.CreateDefaultBuilder()
.UseUrls(serviceUrl)
.Configure((IApplicationBuilder app) => {
app.UseRouting();
app.Map("/check", config => { // just a test: it works!
config.Run(async context =>
{
context.Response.ContentType = "text/plain";
byte[] data = System.Text.Encoding.UTF8.GetBytes("OK");
await context.Response.Body.WriteAsync(data, 0, data.Length);
await context.Response.Body.FlushAsync();
});
});
app.UseEndpoints(endpoints =>
{
//endpoints.MapHub<ClockHub>("/hubs/clock"); // ERROR
//endpoints.MapHub<PingHub>("/ping"); // ERROR
//mapHubs(endpoints); // ERROR
});
})
.Build().Run();
}
}
(ClockHub is taken from MS example and PingHub is another simple Hub I tried to use instead of my "injected" Hubs)
It starts the web application properly and it responds properly to the url http://localhost:8090/check.
When I uncomment the calls to enpoint.MapHub() or my cusom Actions I have this error:
System.InvalidOperationException: 'Unable to find the required services. Please add all the required services by calling 'IServiceCollection.AddSignalR' inside the call to 'ConfigureServices(...)' in the application startup code.'
2nd try:
Seems like service.AddSignalR() is not doing its job, so I added this in SignalRWebHostCreator:
.Configure((IApplicationBuilder app) => {
app.ApplicationServices = services.BuildServiceProvider();
and now I have this error:
System.InvalidOperationException: 'Unable to resolve service for type 'System.Diagnostics.DiagnosticListener' while attempting to activate 'Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware'.'
that at least has a callstack:
_This exception was originally thrown at this call stack:
Microsoft.Extensions.Internal.ActivatorUtilities.ConstructorMatcher.CreateInstance(System.IServiceProvider)
Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance(System.IServiceProvider, System.Type, object[])
Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.UseMiddleware.AnonymousMethod__0(Microsoft.AspNetCore.Http.RequestDelegate)
Microsoft.AspNetCore.Builder.ApplicationBuilder.Build()
Microsoft.AspNetCore.Hosting.WebHost.BuildApplication()
Microsoft.AspNetCore.Hosting.WebHost.StartAsync(System.Threading.CancellationToken)
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(System.Threading.Tasks.Task)
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(System.Threading.Tasks.Task)
System.Runtime.CompilerServices.TaskAwaiter.GetResult()_
If I add services.AddSingleton(new System.Diagnostics.DiagnosticListener("diagnostic listener")); I can use endpoints.MapHub(..) without errors but now a call to http://8090/check returns a 500 internal error, so I don't think this is the right way to solve the issue.
I found some example using WebApp from Microsoft.Owin.hosting.
It requires Microsoft.Owin.4.1.0, Microsoft.Owin.Hosting.4.1.0 and Owin.1.0.0 and the last one require Net Framework 4.6.1, I don't want this.
I have included Microsoft.AspNetCore.Owin.3.1.2 (100% .NET Core) but that does not offer WebApp or something similar.

Answer 1

I started experiencing same error when I upgraded nuget EFCore package to new version.
I noticed, that in my bin directory, a System.Diagnostics.DiagnosticSource.dll appeared, while when I downgraded - it disappeared.
I suspect, that DiagnosticListener type from old assembly version is registered in DI container, while on activation newer version is expected. Or reverse - I didn't dig that deep.
My solution was to revert EFCore to match Product version of System.Diagnostics.DiagnosticSource.dll so it will not appear in bin folder.