Monitor Blazor Server circuit activity

[guardrex]

Fixes #28982

Mackinnon ... this looks like your bits. Half the time, I'll get the PU assignment via Artak. On this one, I think he'll ask you to look. This comes right from Dan's blog post, so it's probably ok as a basic guide. Are there more feature nits and bits that we need to discuss here?

https://devblogs.microsoft.com/dotnet/asp-net-core-updates-in-dotnet-8-preview-3/#monitor-blazor-server-circuit-activity

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Internal previews

📄 File	🔗 Preview link
aspnetcore/blazor/fundamentals/dependency-injection.md	ASP.NET Core Blazor dependency injection
aspnetcore/blazor/fundamentals/signalr.md	ASP.NET Core Blazor SignalR guidance
aspnetcore/blazor/security/server/additional-scenarios.md	ASP.NET Core Blazor Server additional security scenarios

[MackinnonBuck]

This looks great! Just a small suggestion.

I don't think there's anything else this PR needs to cover 🙂

[guardrex]

@MackinnonBuck ... I think we have a bit more to look at and resolve on this one.

Two things leap out now that I know what "there's an existing pattern for accessing circuit-scoped services" was referring to.

I've updated the PR for the following, but you'll need to look and see if iNsAnItY 😵 has taken over the small 🦖🧠...

1. Although it's the same approach, the content and examples probably should be grouped with their subject matter and cross-linked ...

   • The SignalR topic has Monitor circuit activity (Blazor Server) with its IdleCircuitHandler example.
   • The DI topic has Access Blazor services from a different DI scope with its CircuitServicesAccessor example.
   • The Blazor Server Additional scenarios topic has Access AuthenticationStateProvider in outgoing request middleware with its AuthenticationStateHandler example.

2. The first two additions, SignalR and DI examples, seem straightforward. However, the third is something that I have less familiarity with because I spend much of my time in auth scenarios for the WASM hosting model and not implementing DelegatingHandler for Blazor Server apps. AFAICT, the AuthenticationStateHandler is for outgoing middleware request processing, as I have on the PR now, but I could be totally off base on that use case. I hacked up a complete example of it by making it create a custom header for the authenticated user's name. If that is incorrect, what's the use case and what is the complete example for it?

If you want to look at the published previews, they can be reached with the following links (these link directly to the sections) ...

• https://review.learn.microsoft.com/en-us/aspnet/core/blazor/fundamentals/signalr?branch=pr-en-us-28983#monitor-circuit-activity-blazor-server
• https://review.learn.microsoft.com/en-us/aspnet/core/blazor/fundamentals/dependency-injection?branch=pr-en-us-28983#access-blazor-services-from-a-different-di-scope
• https://review.learn.microsoft.com/en-us/aspnet/core/blazor/security/server/additional-scenarios?branch=pr-en-us-28983#access-authenticationstateprovider-in-outgoing-request-middleware)

[guardrex]

@MackinnonBuck ... I think you should take a look at the updated layout. I'm primarily concerned about item 2 above ☝️. I may have guessed correctly on the implementation of the AuthenticationStateHandler, but I think u should confirm if I went the right way.

[MackinnonBuck]

@guardrex I think the updated layout looks great. Regarding the AuthenticationStateHandler example, I wonder if we could get @javiercn's opinion on that. Javier, what do you think? Do we need a full example for this, or can we assume that if a customer needs this, they already have a specific scenario in mind?

[guardrex]

Thanks @MackinnonBuck ... I like what I wrote (and the example) in the Access AuthenticationStateProvider in outgoing request middleware section. If it's good, I hope we can keep it. I think 🤔 it works ..... maybe 🤣 ... the 🙏 server gods 🙏 hopefully will smile on that coverage.

[guardrex]

Thanks @javiercn.

@danroth27 ... awaiting final sign-off.

MERGING NOW! 🏃