Log debug information when queue events time out due to lingering wai…

…tUntil tasks

src/workerd/api/queue.c++

@@ -523,6 +523,12 @@ kj::Promise<WorkerInterface::CustomEvent::Result> QueueCustomEventImpl::run(
   // reuse the scheduled worker logic and timeout for now.
   auto completed = co_await incomingRequest->finishScheduled();
 
+  // Log some debug info if the queue handler completed but other waituntils did not
+  if (!completed && queueEventHolder->event->getIsQueueHandlerComplete()) {
+    auto taskTrace = incomingRequest->getContext().getWaitUntilTasks().trace();
+    KJ_LOG(WARNING, kj::str("Queue event timed out with lingering waitUntil tasks:\n", taskTrace));
+  }
+
   co_return WorkerInterface::CustomEvent::Result {
     .outcome = completed ? context.waitUntilStatus() : EventOutcome::EXCEEDED_CPU,
   };