Fix concurrent timer race condition in InMemoryOrchestrationService

[nytian]

Fix a thread-safety bug in ReadyToRunQueue where a non-thread-safe Dictionary<string, object> was accessed concurrently from multiple threads, causing orchestrations with identical timer FireAt timestamps to hang indefinitely. Update Dictonary to ConcurrentDictionary for thread-safe operations.

[Copilot]

Pull request overview

Fixes a concurrency bug in the in-memory test host’s orchestration scheduling path by making the “ready-to-run” deduplication tracking thread-safe, preventing potential hangs when multiple orchestrations are scheduled concurrently (e.g., timers firing at the same time).

Changes:

• Replaced a non-thread-safe Dictionary with a ConcurrentDictionary for ReadyToRunQueue readiness tracking.
• Updated removal logic to use TryRemove to match the concurrent collection API.
• Bumped Microsoft.DurableTask.InProcessTestHost package version to 0.2.1-preview.1.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/InProcessTestHost/Sidecar/InMemoryOrchestrationService.cs	Makes ready-instance tracking thread-safe to prevent concurrency-related hangs in scheduling.
src/InProcessTestHost/InProcessTestHost.csproj	Increments package version to reflect the bug fix.

[Copilot]

Pull request overview

Fixes a concurrency issue in the in-memory test host orchestration scheduler where non-thread-safe tracking of “ready” instances could cause orchestrations with identical timer FireAt timestamps to hang, and adds regression tests to validate correct completion under timer contention.

Changes:

• Replace ReadyToRunQueue’s non-thread-safe Dictionary with a ConcurrentDictionary and update removal logic accordingly.
• Add new tests that schedule multiple orchestrations/sub-orchestrations with identical timer fire times and assert they all complete.
• Bump the Microsoft.DurableTask.InProcessTestHost package version.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
test/InProcessTestHost.Tests/ConcurrentTimerTests.cs	Adds regression tests for concurrent timers with identical FireAt timestamps.
src/InProcessTestHost/Sidecar/InMemoryOrchestrationService.cs	Makes ReadyToRunQueue’s instance tracking thread-safe using ConcurrentDictionary.
src/InProcessTestHost/InProcessTestHost.csproj	Updates package version to include the fix.