Fix parallel bundle cancellation hang

[mikaelweave]

Description

Batch/transaction bundle parallel operations could hang until the max bundle execution timeout when a parallel worker observed cancellation because the worker only logged OperationCanceledException and did not stop the shared operation. This PR treats the first cancelled parallel worker as terminal for that bundle operation: it marks bundle statistics cancelled, cancels/releases the bundle orchestrator operation, cancels the linked request token so sibling workers observing RequestAborted stop promptly, and rethrows so Task.WhenAll propagates cancellation.

Adds focused regression coverage for a parallel batch where one operation throws OperationCanceledException while a sibling request waits on RequestAborted.

Related issues

Addresses ADO 192125.

Testing

• dotnet test .\src\Microsoft.Health.Fhir.Api.UnitTests\Microsoft.Health.Fhir.R4.Api.UnitTests.csproj --filter "FullyQualifiedName~GivenABundleRequest_WhenParallelOperationIsCanceled_ThenParallelProcessingCompletesPromptly" --no-restore --verbosity minimal
• Result: exit 0; Test summary: total: 2594, failed: 0, succeeded: 2594, skipped: 0

FHIR Team Checklist

• Update the title of the PR to be succinct and less than 65 characters
• Add a milestone to the PR for the sprint that it is merged (i.e. add S47)
• Tag the PR with the type of update: Bug, Build, Dependencies, Enhancement, New-Feature or Documentation
• Tag the PR with Open source, Azure API for FHIR (CosmosDB or common code) or Azure Healthcare APIs (SQL or common code) to specify where this change is intended to be released.
• Tag the PR with Schema Version unchanged. No SQL scripts or schema changes are included.
• ADR: N/A. This is a scoped runtime cancellation handling fix and does not change system design assumptions.
• CI is green before merge
• Review squash-merge requirements

Semver Change (docs)

Patch

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.38%. Comparing base (0c27653) to head (f60187f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5572      +/-   ##
==========================================
+ Coverage   77.29%   77.38%   +0.08%     
==========================================
  Files         993      993              
  Lines       36418    36431      +13     
  Branches     5518     5520       +2     
==========================================
+ Hits        28151    28191      +40     
+ Misses       6907     6879      -28     
- Partials     1360     1361       +1     

see 9 files with indirect coverage changes

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