In certain usage scenarios where the prefetch is very small, the prefetchExtension is used to ensure messages continue to flow to the broker even though the prefetch is exceeded e.g. clients consuming multiple messages within a single transaction.

After a transaction is complete i would expect the prefetchExtension for a topic subscription to be returned to zero.

Stomp messages acked in transaction, it seems the prefetchExtension not being reset to zero.

Side effect: If the prefetchExtension is used during the broker calculation to detect if a consumer will be sent more messages and in turn when the broker is deciding if a consumer is slow.