Avoid pausing circuit simultaneously with disposing of it

[ilonatommy]

Prevent scope-related operations on disposed circuit

 ---> System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'IServiceProvider'.
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ThrowHelper.ThrowObjectDisposedException()
 at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Microsoft.AspNetCore.Components.Server.Circuits.CircuitPersistenceManager.PauseCircuitAsync(CircuitHost circuit, Boolean saveStateToClient, CancellationToken cancellation) in /home/vsts/work/1/s/src/Components/Server/src/Circuits/CircuitPersistenceManager.cs:line 25

Description

The problem occurs only when we try to pause the circuit after it was already disposed. It can happen in scenarios:

• Race between eviction and pausing.
• Race between termination and pausing.
• Race between two pauses.

The test call these actions synchronously (they await), so that the reproduction is stable. The real race was observed on CI with a frequency of ~20 hits per week.

Fix

• All disposal actions happen on a single-threaded dispatcher:
  

  aspnetcore/src/Components/Server/src/Circuits/CircuitHost.cs

  Line 200 in 0f963e9

  await Renderer.Dispatcher.InvokeAsync(async () =>

  
  Wrapping pause logic in the dispatcher invoke prevents it from running concurrently with disposal that comes from e.g. termination or eviction.
  - Even if pause will not run concurrently with disposal, it can still run just after disposal happened - see the tests. To prevent it from trying to discover services in a disposed DI scope, we check CircuitHost disposal flag. removed after the discussion - I could not find any evidence that pause can happen after disposal in real life.

Fixes - let's keep it open for some time: #62672

Frequency of failures on CI before this fix for reference:

[Copilot]

Pull Request Overview

This PR fixes race conditions that occur when attempting to pause a circuit after it has already been disposed, preventing exceptions from being thrown when resolving services from disposed DI scopes.

• Wraps pause logic in the circuit's single-threaded dispatcher to prevent concurrent execution with disposal operations
• Adds a disposal check before attempting to resolve services during pause operations
• Includes comprehensive test coverage for various race condition scenarios

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/Components/Server/src/Circuits/CircuitPersistenceManager.cs	Wraps pause logic in dispatcher invoke and adds disposal check
src/Components/Server/src/Circuits/CircuitHost.cs	Adds internal method to expose disposal state
src/Components/Server/src/Circuits/CircuitRegistry.cs	Changes method visibility from private to internal for testing
src/Components/Server/test/Circuits/CircuitRegistryTest.cs	Adds comprehensive test coverage for race condition scenarios

[ilonatommy]

e2e on 3rd run passed, re-merging

[pavelsavara]

nice