[jira] [Created] (AMQ-6579) Expired messages counting as Dispatched on TopicSubscription

["Vasco Veloso (JIRA)" <ji...@apache.org>]

Vasco Veloso created AMQ-6579:
---------------------------------

             Summary: Expired messages counting as Dispatched on TopicSubscription
                 Key: AMQ-6579
                 URL: https://issues.apache.org/jira/browse/AMQ-6579
             Project: ActiveMQ
          Issue Type: Bug
    Affects Versions: 5.14.3, 5.15.0
            Reporter: Vasco Veloso


When a TopicSubscription is configured with a limit on the number of pending messages, it will try to eagerly evict expired messages before dispatching them.

{code:title=TopicSubscription.java:169}
if (!matched.isEmpty() && matched.size() > max) {
  removeExpiredMessages();
}
{code}

When {{TopicSubscription#removeExpiredMessages}} detects an expired message, it will remove it but will increment the counter of dispatched messages as well.

{code:title=TopicSubscription.java:169}
if (node.isExpired()) {
  matched.remove();
  getSubscriptionStatistics().getDispatched().increment();
  node.decrementReferenceCount();
  if (broker.isExpired(node)) {
    ((Destination) node.getRegionDestination()).getDestinationStatistics().getExpired().increment();
    broker.messageExpired(getContext(), node, this);
  }
  break;
}
{code}

However this has the side effect of affecting the result of {{getDispatchedQueueSize()}} and therefore {{isFull()}}. These counters will now reflect a new dispatched message that has actually been dropped.

In the worst case scenario slow consumers will no longer receive messages because they are "full" when in fact they have nothing to process.

Am I correct in concluding that expired messages must not count towards the dispatched value?

I have made a quick change, removing the increment, and things look good so far. However I am worried that I may be missing some side effect or specification detail.



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