I have a MassTransitStateMachine that orchestrates a process which involves creating multiple events.
Once all of the events are done, I want the state to transition to a 'clean up' phase.
Here is the relevant state declaration and filter function:
During(ImportingData,
When(DataImported)
// When we get a data imported event, mark this source as done.
.Then(MarkImportCompletedForLocation),
When(DataImported, IsAllDataImported)
// Once all are done, we can transition to cleaning up...
.Then(CleanUpSources)
.TransitionTo(CleaningUp)
);
...snip...
private static bool IsAllDataImported(EventContext<DataImportSagaState, DataImportMappingCompletedEvent> ctx)
{
return ctx.Instance.Locations.Values.All(x => x);
}
So while the state is ImportingData, I expect to receive multiple DataImported events. Each event marks its location as done so that that IsAllDataImported method can determine if we should transition to the next state.
However, if the last two DataImported events arrive at the same time, the handler for transitioning to the CleaningUp phase fires twice, and I end up trying to perform the clean up twice.
I could solve this in my own code, but I was expecting the state machine to manage this. Am I doing something wrong, or do I just need to handle the contention myself?