Add pre-scheduling and retry handler cancellation support for activities and sub-orchestrators

[Copilot]

Summary

What changed?

Added CancellationToken support to the TaskOptions class for activities, sub-orchestrators, and retry handlers. The implementation provides pre-scheduling cancellation checks and passes cancellation tokens to retry handlers.

Why is this change needed?

The TaskOptions class had a CancellationToken parameter that was not wired up. This change implements the cancellation functionality to allow orchestrators to cancel activities, sub-orchestrators, and stop retrying when requested.

Important limitation: Due to the durable orchestrator execution model, cancellation only works at specific points (pre-scheduling and in retry handlers), not mid-execution while the orchestrator is yielded.

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Project checklist

• Release notes are not required for the next release
• Backport is not required
• All required tests have been added/updated (unit tests, E2E tests)
• Breaking change? No

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AI-assisted code disclosure (required)

Was an AI tool used? (select one)

• Yes, an AI agent generated most of this PR

If AI was used:

• Tool(s): GitHub Copilot AI Agent
• AI-assisted areas/files:
  • src/Abstractions/TaskOptions.cs - Added CancellationToken property with XML documentation
  • src/Worker/Core/Shims/TaskOrchestrationContextWrapper.cs - Implemented cancellation logic in CallActivityAsync and CallSubOrchestratorAsync
  • test/Grpc.IntegrationTests/CancellationTests.cs - Created comprehensive integration tests
• What you changed after AI output:
  • Removed ineffective WaitForTaskWithCancellation method after code review identified it wouldn't work with orchestrator execution model
  • Fixed line endings (CRLF) in TaskOptions.cs
  • Fixed documentation example syntax error
  • Added additional test cases based on review feedback

AI verification (required if AI was used):

• I understand the code and can explain it
• I verified referenced APIs/types exist and are correct
• I reviewed edge cases/failure paths (timeouts, retries, cancellation, exceptions)
• I reviewed concurrency/async behavior
• I checked for unintended breaking or behavior changes

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Testing

Automated tests

• Result: Passed - All 6 integration tests pass successfully

Test coverage:

1. ActivityCancellation - Pre-scheduling cancellation for activities
2. SubOrchestratorCancellation - Pre-scheduling cancellation for sub-orchestrators
3. RetryHandlerReceivesCancellationToken - Token passed to retry handlers
4. RetryHandlerCanStopOnCancellation - Retry handler can check token and stop retrying
5. RetryHandlerReceivesCancelledTokenFromOutside - Token cancelled outside handler caught by pre-check
6. MultipleActivitiesInLoopWithCancellation - Main use case: loop exits when token cancelled (demonstrates pre-scheduling cancellation preventing remaining activities from being scheduled)

Manual validation (only if runtime/behavior changed)

• N/A - Behavior validated through comprehensive integration tests

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Notes for reviewers

Implementation details:

• Pre-scheduling check: Throws TaskCanceledException if token is already cancelled before scheduling
• Retry handler integration: Passes token via RetryContext so handlers can check cancellation
• No mid-execution cancellation: Once scheduled, orchestrator yields and cannot respond to cancellation until next execution point

Key changes after review:

• Removed WaitForTaskWithCancellation method - didn't work due to orchestrator yielding during await
• Simplified to direct awaits with pre-scheduling checks only
• Updated documentation to clearly explain limitations

Design considerations:

• Cancellation is cooperative (not forceful)
• Implementation is deterministic and replay-safe
• Parent cancellation does not cascade to sub-orchestrations
• Works with both declarative (RetryPolicy) and imperative (RetryHandler) retry patterns

Main use case:

The primary use case for this feature is processing multiple items in a loop. When a cancellation token is cancelled, the orchestrator can exit the loop instead of continuing to schedule remaining activities. This is demonstrated in the MultipleActivitiesInLoopWithCancellation test.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Activity and sub-orchestrator cancellation support</issue_title>
<issue_description>The TaskOptions class provided when scheduling activities and sub-orchestration calls supports providing a CancellationToken. However, it's not yet wired up to actually cancel the task. This issue tracks adding support for cancellation.

• Implement the feature for activity calls, sub-orchestrator calls, and retry handlers.
• Add detailed <remarks> documentation with examples for how cancellation can be used.
• Add tests that cover all the scenarios supported by task cancellation</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Activity and sub-orchestrator cancellation support #7

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[Copilot]

Pull request overview

This PR implements cancellation support for activities, sub-orchestrators, and retry handlers by wiring up the previously unused CancellationToken parameter in the TaskOptions class. The implementation provides pre-scheduling cancellation checks and post-scheduling cancellation via a Task.WhenAny pattern, enabling cooperative cancellation of orchestrator tasks.

Key changes:

• Added CancellationToken property to TaskOptions with comprehensive XML documentation and usage examples
• Implemented cancellation logic in TaskOrchestrationContextWrapper including pre-scheduling checks and the WaitForTaskWithCancellation helper method
• Added four integration tests covering activity cancellation, sub-orchestrator cancellation, and retry handler integration scenarios

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/Abstractions/TaskOptions.cs	Added CancellationToken property with extensive documentation and examples, updated copy constructor to include the new property
src/Worker/Core/Shims/TaskOrchestrationContextWrapper.cs	Implemented cancellation logic for activities and sub-orchestrators with pre-scheduling checks, added WaitForTaskWithCancellation helper method, integrated cancellation token into retry handler flow
test/Grpc.IntegrationTests/CancellationTests.cs	New test file with comprehensive integration tests for activity cancellation, sub-orchestrator cancellation, and retry handler cancellation scenarios

[YunchuWang]

@copilot address the comment

[Copilot]

@copilot address the comment

Both issues in this thread have already been addressed in commit aa94a56:

1. Chinese full-width comma replaced with ASCII comma
2. Documentation example corrected to use TaskRetryOptions.FromRetryHandler()

The code builds successfully and all tests pass.

[YunchuWang]

@copilot why pr shows full file of src/Abstractions/TaskOptions.cs is changed, thats not right, fix

[Copilot]

@copilot why pr shows full file of src/Abstractions/TaskOptions.cs is changed, thats not right, fix

Fixed in commit f68ff62. The issue was that the previous commits inadvertently changed line endings from CRLF to LF, causing git to show the entire file as modified. I've restored the CRLF line endings while keeping all functional changes. The PR now shows only 62 lines added (the actual CancellationToken property and documentation) instead of the full file replacement.

[YunchuWang]

@copilot does this really cancel an activity or suborch? when awaiting activity or suborch, the durable worker will yield the execution waiting for activity or suborch new workitem then resume execution. during that time if you try to cancel using the canceltoken, it wont cancel anything?

[YunchuWang]

@copilot WaitForTaskWithCancellation is useless then, // Wait for either the task to complete or cancellation
Task completedTask = await Task.WhenAny(task, cancellationTcs.Task);

    // If cancellation won, throw TaskCanceledException
    if (completedTask == cancellationTcs.Task)
    {
        throw new TaskCanceledException("The task was cancelled.");
    } this is cancellationtcs only if it is cancellated task before running whenany since when running whenany the activity will be immeidatelly scheduled and you cant cancel it anymore. correct me if i am wrong, 

[Copilot]

@copilot WaitForTaskWithCancellation is useless then, // Wait for either the task to complete or cancellation
Task completedTask = await Task.WhenAny(task, cancellationTcs.Task);
...

You're absolutely correct. The WaitForTaskWithCancellation method is indeed useless. Since ScheduleTask immediately schedules the activity and returns a durable task, when we await it the orchestrator yields. During that yield, the orchestrator code isn't running, so the cancellationToken.Register() callback can never fire. The Task.WhenAny will always return the activity task, never the cancellation task.

The only meaningful cancellation happens at the pre-scheduling check (line 158). I'll remove WaitForTaskWithCancellation and simplify the code to just do the pre-check and then directly await the scheduled tasks.

[YunchuWang]

@copilot WaitForTaskWithCancellation is useless then, // Wait for either the task to complete or cancellation
Task completedTask = await Task.WhenAny(task, cancellationTcs.Task);
...

You're absolutely correct. The WaitForTaskWithCancellation method is indeed useless. Since ScheduleTask immediately schedules the activity and returns a durable task, when we await it the orchestrator yields. During that yield, the orchestrator code isn't running, so the cancellationToken.Register() callback can never fire. The Task.WhenAny will always return the activity task, never the cancellation task.

The only meaningful cancellation happens at the pre-scheduling check (line 158). I'll remove WaitForTaskWithCancellation and simplify the code to just do the pre-check and then directly await the scheduled tasks.

yes make the change @copilot

[Copilot]

@copilot WaitForTaskWithCancellation is useless then, // Wait for either the task to complete or cancellation
Task completedTask = await Task.WhenAny(task, cancellationTcs.Task);
...

Already completed in commit 37d523f. The WaitForTaskWithCancellation method has been removed, and both CallActivityAsync and CallSubOrchestratorAsync now directly await the scheduled tasks with only the pre-scheduling cancellation check. The documentation has also been updated to accurately reflect the limitations.

[YunchuWang]

@copilot add testcase to cancel the token outside the retryhandler

[YunchuWang]

@copilot add testcase for Multiple activities in a loop - The main use case for pre-check. once token is cancelled, the loop should exit instead of continuing calling remaining activities

[YunchuWang]

@copilot update pr description to follow .github/PULL_REQUEST_TEMPLATE.md

[Copilot]

@copilot add testcase to cancel the token outside the retryhandler

Added in commit 0e911a1. The new test RetryHandlerReceivesCancelledTokenFromOutside demonstrates that when a cancellation token is cancelled outside the retry handler (in orchestrator code before calling CallActivityAsync), the pre-scheduling check catches it and throws TaskCanceledException immediately. The retry handler is never called in this scenario, which is the expected behavior given the orchestrator execution model.

[YunchuWang]

@copilot

[Copilot]

@copilot add testcase for Multiple activities in a loop - The main use case for pre-check. once token is cancelled, the loop should exit instead of continuing calling remaining activities

Added in commit a34d209. The new test MultipleActivitiesInLoopWithCancellation demonstrates the main use case for pre-scheduling cancellation: an orchestrator processes 10 items in a loop, cancels the token after 3 items, and the loop exits cleanly instead of continuing to call the remaining activities. The test verifies that exactly 3 activities were invoked and the loop terminated with a cancellation message.

@copilot update pr description to follow .github/PULL_REQUEST_TEMPLATE.md

Updated PR description in commit a34d209 to follow the template at .github/PULL_REQUEST_TEMPLATE.md. The description now includes all required sections: Summary, Project checklist, AI-assisted code disclosure, Testing, and Notes for reviewers.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.