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fix(sessions): tidy replay filter/comment; zero OldestAvailableSequence when no gap

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- EventStreamService: remove dead per-item sequence guard in the replay
  loop (RegisterWithReplay already returns only events > afterSequence)
  and correct the comment that falsely claimed a "per-item constraint
  filter" is applied; the event stream has no per-event constraint
  filtering today.
- SessionEventDistributor.RegisterWithReplay: set oldestAvailableSequence=0
  when gap==false so the implementation matches the documented contract
  (OldestAvailableSequence is meaningful only when Gap is true).
  Update the two RegisterWithReplay tests that asserted the old non-zero
  value in the no-gap path.
- RegisterSubscriber: remove stray blank line at method entry.
- SessionEventDistributorTests: add RegisterWithReplay_AfterDispose_
  ThrowsObjectDisposedException to pin nested-lock disposal behavior.
This commit is contained in:
Joseph Doherty
2026-06-16 07:28:37 -04:00
parent 36ab8d15f1
commit c7a7cd1e5e
3 changed files with 36 additions and 16 deletions
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src/ZB.MOM.WW.MxGateway.Server/Grpc/EventStreamService.cs
+6 -10
View File
@@ -132,16 +132,12 @@ public sealed class EventStreamService(
foreach (MxEvent replayedEvent in replayedEvents)
{
// Replayed events pass through the SAME per-item filter the live loop applies,
// so a constrained/resuming caller never sees a replayed event it could not
// have seen live. The watermark dropped events at/below the requested
// AfterWorkerSequence; the snapshot already excluded those, but this keeps the
// filter identical for replay and live.
if (replayedEvent.WorkerSequence <= request.AfterWorkerSequence)
{
continue;
}
// RegisterWithReplay already returns only events strictly newer than
// AfterWorkerSequence, so no per-item sequence guard is needed here.
// There is no per-event constraint filter on the event stream: events are
// fanned as-is by the distributor pump. The only dedup watermark is the
// LiveResumeSequence applied in the live loop below (to drop any event
// that was both replayed and raced into the live channel).
yield return replayedEvent;
}
src/ZB.MOM.WW.MxGateway.Server/Sessions/SessionEventDistributor.cs
+5 -4
View File
@@ -295,7 +295,6 @@ public sealed class SessionEventDistributor : IAsyncDisposable
private IEventSubscriberLease RegisterSubscriber(Subscriber subscriber)
{
// The disposed check AND the map add happen under the same lock with no await
// in between. DisposeAsync sets _disposed=true under this same lock before it
// calls CompleteAllSubscribers, so once disposal has begun no further subscriber
@@ -424,13 +423,15 @@ public sealed class SessionEventDistributor : IAsyncDisposable
if (_replayBuffer.Count == 0)
{
oldestAvailableSequence = 0;
gap = _anyEventSeen && afterSequence < _highestSequenceSeen;
oldestAvailableSequence = 0; // meaningful only when gap == true; 0 here since nothing is retained
}
else
{
oldestAvailableSequence = _replayBuffer.First!.Value.Event.WorkerSequence;
gap = oldestAvailableSequence > 0 && afterSequence < oldestAvailableSequence - 1;
ulong oldestRetained = _replayBuffer.First!.Value.Event.WorkerSequence;
gap = oldestRetained > 0 && afterSequence < oldestRetained - 1;
// Per the contract on OldestAvailableSequence: meaningful only when gap == true.
oldestAvailableSequence = gap ? oldestRetained : 0;
foreach (ReplayEntry entry in _replayBuffer)
{