Clear persisted output during Azure Storage rewind

[wangbill (YunchuWang)]

Summary

• Remove the persisted Output property when Azure Storage rewinds a failed orchestration to Pending.
• Read the complete Instances row and use an ETag-guarded Azure Table Replace, preserving unrelated and unknown properties while rejecting concurrent changes with 412 instead of clobbering them.
• Add raw-storage unit and Azurite coverage for property deletion, ETag conflicts, missing output, repeated rewind, later terminal output, same-instance-ID reuse, and large output storage.

Persisted behavior

This is deletion at the provider persistence source, not API-layer hiding. Before this change, UpdateStatusForRewindAsync used Merge, which could update RuntimeStatus but could not remove the existing Output property. After this change, the Instances row has no Output property while the rewound orchestration is pending. A later Completed or Failed checkpoint writes its new output normally.

No host, client, serializer, or API projection suppression is added.

Large-output blobs

The large-output blob is not deleted by this change. The Instances-table URL is deleted, but the exact gzip blob remains because the rewound ExecutionCompleted history row still stores ResultBlobName, and history loading eagerly dereferences that property before deserializing the rewritten GenericEvent.

Deleting that blob without first coordinating removal of every history reference can break replay/history reads. Azure Table and Blob updates are not transactional, so crash- and retry-safe reclamation needs a durable cleanup ledger plus execution/write fencing (or a broader history-storage design change). The focused regression verifies that the exact history-referenced blob remains available. Existing purge behavior still removes all blobs for the instance.

Existing instance ID reuse

Current main already handles an accepted new execution safely: SetNewExecutionAsync builds a fresh row and ETag-replaces the old row, which removes the previous Output. A raw Azurite regression now protects that invariant; no additional production change was needed for this path.

Tests

• dotnet test Test\DurableTask.AzureStorage.Tests\DurableTask.AzureStorage.Tests.csproj -f net8.0 --filter "Name~Rewind" --no-restore -p:NoWarn=NU1605
• dotnet test Test\DurableTask.AzureStorage.Tests\DurableTask.AzureStorage.Tests.csproj -f net48 --filter "Name~Rewind" --no-restore -p:NoWarn=NU1605
• dotnet test Test\DurableTask.AzureStorage.Tests\DurableTask.AzureStorage.Tests.csproj -f net8.0 --filter "FullyQualifiedName~RewindOutputTrackingStoreTests" --no-restore -p:NoWarn=NU1605
• dotnet test Test\DurableTask.AzureStorage.Tests\DurableTask.AzureStorage.Tests.csproj -f net48 --filter "FullyQualifiedName~RewindOutputTrackingStoreTests" --no-restore -p:NoWarn=NU1605

Consumption

After this change ships in a new Microsoft.Azure.DurableTask.AzureStorage package, Azure/azure-functions-durable-extension must update its provider dependency from 2.9.1 to that released version to consume the fix.

Related: Azure/azure-functions-durable-extension#968

[Copilot]

🟢 Approval recommended

The core behavior change is narrowly scoped, uses ETag-guarded replaces to avoid concurrency clobbering, and is backed by targeted unit and Azurite scenario coverage.

Pull request overview

This PR fixes Azure Storage rewind persistence by ensuring the Instances-table Output property is physically removed when rewinding a terminal orchestration back to Pending, using an ETag-guarded full-entity Replace to avoid clobbering concurrent updates and to preserve unrelated properties.

Changes:

• Update AzureTableTrackingStore.UpdateStatusForRewindAsync to read the full Instances row, remove Output, and Replace using the current ETag (instead of Merge).
• Add raw-storage unit coverage for output deletion, idempotency when output is missing, and ETag conflict propagation.
• Add Azurite scenario coverage for large-output rewinds to ensure the instance Output is removed while the history-referenced blob remains available.

File summaries

File	Description
src/DurableTask.AzureStorage/Tracking/AzureTableTrackingStore.cs	Switch rewind status update from Merge to ETag-guarded Replace and remove persisted Output property.
test/DurableTask.AzureStorage.Tests/RewindOutputTrackingStoreTests.cs	Add raw Azurite tests validating Output removal, idempotency, terminal rewrites, and instance ID reuse behavior.
test/DurableTask.AzureStorage.Tests/AzureTableTrackingStoreTest.cs	Add mock-based unit tests asserting full-entity Replace with current ETag and 412 propagation behavior.
test/DurableTask.AzureStorage.Tests/AzureStorageScenarioTests.cs	Add end-to-end coverage for large-output rewind: instance Output cleared while shared history blob remains.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 2
• Review effort level: Lite

---

💡 Add a code-review agent skill for context-aware, tailored reviews. Learn more in the docs.