The broker checks for slow subscribers by checking its dispatch queue size against the prefetch size. If the dispatch queue is greater than or equal to the prefetch size the broker treats this subscription is a slow subscriber.
However if the subscribers prefetch size is "1" then the subscription will get treated as a slow subscriber even if the messages do not remain long in the subscription. This can result in a lot of warning log statements
and slow consumer advisory messages being generated if "AdvisoryForSlowConsumers" has been turned on.