When replaying a group of parked messages and the message is parked, the event is still retried

[anthonyMc11]

Describe the bug
When you replay a group of parked message and N'ack to be parked, this is ignore and the event is retried

To Reproduce

1. create a subscriber to a persistent subscription - timeout (10000ms)
2. code the subscription to handle the event with a task.Delay until AFTER the timeout to park the message (20000ms)
3. add an event to the stream
4. the event will be retried
5. both the original attempt and the retry now park the message
6. the parked stream has 1 copy of the event
7. click replay parked messages in the UI
8. the the event is retried as it's not been n'acked yet
9. the original and the retry n'ack the event
10. the event is returned to the parked queue with a new event number as a single copy (success scenario and desired behaviour)
11. add 4 more events
12. the parked queue now has 5 events
13. click replayed events in the UI
14. continue to n'ack the message to park
15. the events are retried the maximum numbers of retries ( failure scenario they ignore the n'ack to park)

Expected behaviour
groups of events are only retried until n'acked

Actual behaviour
The event is retried for the number of times the subscription is set to

Config/Logs/Screenshots
these are the logs for a single parked event, you can see it is parked, and then I replay the parked again and it is still replaying event 53

these are the logs for 5 events, as you can see the event 53 is now sent 11 times (3 times in this screen shot) without receiving a new parked event number

subscription set up

EventStore details

• EventStore server version: 21.10.8.0

• Operating system: Linux

• EventStore client version (if applicable):
  5.0.9
  Additional context

code example below

 private async Task ProcessEvent(ResolvedEvent sourceEvent)
        {
            Log.Information($"Event received: {sourceEvent.Event.EventStreamId}:{sourceEvent.Event.EventNumber} Link.StreamId:{sourceEvent.Link?.EventStreamId}:{sourceEvent.Link?.EventNumber}");
            Log.Information("event received, start sleeping");
            await Task.Delay(20000);

            Log.Information("park handling");
             Log.Warning($"Error handling event:");
            Subscription?.Fail(resolvedEvent, PersistentSubscriptionNakEventAction.Skip,   "");
        }

[ylorph]

possibility : the client side buffer that does not clear the buffer, so the client can get duplicates if the messages are processed too slowly.

[anthonyMc11]

Thanks for your feed back ylorph, I thought so too, however the behaviour does not present itself when only a single event is being replayed, which would surely suffer the same issue with the client side buffer?