fix race condition on OrchestrationRuntimeState.NewEvents #380
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davidmrdavid
approved these changes
Apr 15, 2024
| @@ -876,7 +876,7 @@ async Task<PurgeResult> IOrchestrationServicePurgeClient.PurgeInstanceStateAsync | |||
| InstanceId = workItem.InstanceId, | |||
| BatchStartPosition = messageBatch.BatchStartPosition, | |||
| BatchLength = messageBatch.BatchLength, | |||
| NewEvents = (List<HistoryEvent>)newOrchestrationRuntimeState.NewEvents, | |||
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I wonder if we can (or should) statically enforce that NewEvents should be readonly. That way, we can have more confidence that it is immutable. Is that worth it here?
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I am not aware of an easy (and standard) way to statically enforce this. I think there is a library for immutable collections but I don't really think it is worth the hassle.
src/DurableTask.Netherite/OrchestrationService/NetheriteOrchestrationService.cs
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Co-authored-by: David Justo <david.justo.1996@gmail.com>
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In the current code, the
BatchProcessedevent was copying the listNewEventsfromOrchestrationRuntimeState. However, that list can be mutated when processing more batches. This violates the design principle that events should be immutable, and can lead to race conditions between code that is reading those events (e.g. for serialization) and code that is mutating it.To fix this, we just make a copy of that list when constructing the
BatchProcessedevent.