More Messages In Azure Service Bus Queue than sent

Question

In an attempt to catch and retry transient exceptions when sending to a queue in an azure service bus, I am seeing more messages than sent when sending more than 25,000 messages in a test scenario. I expected that if I did have excess messages, they would be the result of some sort of timeout/retry that actually had reached the message bus the first time.

We are using the .Net Standard Micrososft.Azure.ServiceBus library version 3.0.2

The basic logic in an infinite loop:

1. await sending message to queue
2. break if successful
3. catch exception and test if it is a transient one that benefits from retry
4. wait random time from 1-3 seconds and retry
5. any not caught exception is logged by the caller.

Other notes - in debug, I see many "system.timeout" exceptions, but can't catch them when not running in debug.

  public async Task SendToAzureQueue(Message messageToSend) {

        while (true) {
            try {                    
                await messageSender.SendAsync(messageToSend);
                break;
            }
            catch (Exception ex) when (
                ex is ServerBusyException ||
                ex is ServiceBusCommunicationException ||
                ex is ServiceBusTimeoutException ||
                ex is SessionCannotBeLockedException ||
                ex is SocketException
            ) {
                _logger.Warn($"Transient Exception Thrown. MessageId: {messageToSend.MessageId} - Retrying in 1-10 seconds.\n", ex);
                var randomGenerator = new Random();
                await Task.Delay(randomGenerator.Next(1000, 10000));
            }                
        }
    }

The calling function wraps this with a try/catch (exception)

Here is the code of the integration test that calls the above code:

var graphLogObjects = AutoFixture.CreateMany<GraphlogWithNumericId>(30000);

var tasks = graphLogObjects
            .Select(graphLogEntryDto => _jsonSerializer.Serialize(graphLogEntryDto))
            .Select(dataToSend => graphLogMessageQueue.SendToAzureQueue(Message messageToSend));

await Task.WhenAll(tasks);