QueueStatusListener

```
public interface QueueStatusListener

                    
```
Observes the state of tasks in TaskQueue.
All methods are invoked on a background thread; do not block — listener latency is added to task execution time. The interface is internal and intended for debug / metrics use only.

Method Summary

Modifier and Type	Method	Description
`abstract Unit`	`onTaskAdded(Task<?> task)`	Called when a new task is added to the queue, or a failed task is re-added for retry.
`abstract Unit`	`onTaskStarted(Task<?> task)`	Called when the task started execution on the queue executor.
`abstract Unit`	`onTaskFinished(Task<?> task, QueueResult result)`	Called when the task completed execution — successfully or not (moving back to pending state).
`abstract Unit`	`onTaskDropped(Task<?> task)`	Called when the task is removed from the queue because of reaching the pendingTasksLimit.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - onTaskAdded
```
@WorkerThread() abstract Unit onTaskAdded(Task<?> task)
```
    Called when a new task is added to the queue, or a failed task is re-added for retry.
  - onTaskStarted
```
@WorkerThread() abstract Unit onTaskStarted(Task<?> task)
```
    Called when the task started execution on the queue executor.
  - onTaskFinished
```
@WorkerThread() abstract Unit onTaskFinished(Task<?> task, QueueResult result)
```
    Called when the task completed execution — successfully or not (moving back to pending state).
  - onTaskDropped
```
@WorkerThread() abstract Unit onTaskDropped(Task<?> task)
```
    Called when the task is removed from the queue because of reaching the pendingTasksLimit.