private boolean completedBlockingTasks() {
            if (!(blockingTaskExecutor instanceof ThreadPoolExecutor)) {
                // Cannot determine if there's a blocking task.
                return true;
            }

            final ThreadPoolExecutor threadPool = (ThreadPoolExecutor) blockingTaskExecutor;
            return threadPool.getQueue().isEmpty() && threadPool.getActiveCount() == 0;
        }
Declared as non-volatile because using {@link #pendingResponses} as a memory barrier.
core/src/main/java/com/linecorp/armeria/server/GracefulShutdownSupport.java