Task Execution Backlog from Thread Pool Saturation
warningGrowing queues of tasks waiting for execution across executor pools, indicating thread pool saturation and potential query slowdown as splits wait for processing resources.
Monitor presto_execution_executor_queued_task increasing while presto_execution_executor_active plateaus at or near presto_execution_executor_core_pool_size. Check presto_execution_task_notification_executor_queued_task and presto_execution_management_executor_queued_task for similar patterns. High presto_execution_executor_waiting_splits with stable running_splits suggests backlog.
Increase executor pool sizes through configuration. Scale worker nodes horizontally to distribute load. Review query complexity and split generation - very small splits can overwhelm executors. Consider adjusting split concurrency limits. Monitor for long-running tasks blocking executor threads and implement query timeouts if appropriate.