[improve][broker] add warn log when the delayedMessagesCount is incorrect. (#24460)

Co-authored-by: thetumbled <[email protected]>

Author: thetumbled

pulsar-broker/src/main/java/org/apache/pulsar/broker/delayed/InMemoryDelayedDeliveryTracker.java

@@ -220,6 +220,10 @@ public NavigableSet<Position> getScheduledMessages(int maxMessages) {
             // Reset to initial state
             highestDeliveryTimeTracked = 0;
             messagesHaveFixedDelay = true;
+            if (delayedMessagesCount.get() != 0) {
+                log.warn("[{}] Delayed message tracker is empty, but delayedMessagesCount is {}",
+                        dispatcher.getName(), delayedMessagesCount.get());
+            }
         }
 
         updateTimer();