* decide not to by returning -1L.
 *
 * Task Queues
 * -----------
 *
 * Tasks are bound to the [TaskQueue] they are scheduled in. Each queue is sequential and the tasks
 * within it never execute concurrently. It is an error to use a task in multiple queues.
 */
abstract class Task(
  val name: String,
  val cancelable: Boolean = true,
) {
  // Guarded by the TaskRunner.
  internal var queue: TaskQueue? = null

  }

  /**
   * Wraps a collection of tasks.
   *
   * @throws NullPointerException if any element of {@code tasks} is null
   */
  private <T extends @Nullable Object> ImmutableList<Callable<T>> wrapTasks(
      Collection<? extends Callable<T>> tasks) {
    ImmutableList.Builder<Callable<T>> builder = ImmutableList.builder();
    for (Callable<T> task : tasks) {
      builder.add(wrapTask(task));
    }
    return builder.build();
  }

{* ../../docs_src/background_tasks/tutorial001.py hl[6:9] *}

## Add the background task { #add-the-background-task }

Inside of your *path operation function*, pass your task function to the *background tasks* object with the method `.add_task()`:

{* ../../docs_src/background_tasks/tutorial001.py hl[14] *}

`.add_task()` receives as arguments:

* A task function to be run in the background (`write_notification`).

   * started. Similarly the task will be delayed if the host lacks compute resources.
   *
   * @throws RejectedExecutionException if the queue is shut down and the task is not cancelable.
   */
  fun schedule(
    task: Task,
    delayNanos: Long = 0L,
  ) {
    taskRunner.withLock {
      if (shutdown) {
        if (task.cancelable) {

							task.event.StorageClass, task.objInfo.Bucket, task.objInfo.Name, task.objInfo.VersionID, err))
					}
				}
			} else {
				ts := tierStats{
					TotalSize:   uint64(task.objInfo.Size),
					NumVersions: 1,
				}
				if task.objInfo.IsLatest {
					ts.NumObjects = 1
				}
				t.addLastDayStats(task.event.StorageClass, ts)
			}
			t.activeTasks.Add(-1)

import java.util.logging.Level
import java.util.logging.Logger

internal inline fun Logger.taskLog(
  task: Task,
  queue: TaskQueue,
  messageBlock: () -> String,
) {
  if (isLoggable(Level.FINE)) {
    log(task, queue, messageBlock())
  }
}

internal inline fun <T> Logger.logElapsed(
  task: Task,
  queue: TaskQueue,
  block: () -> T,
): T {
  var startNs = -1L

  /**
   * True if this task faker has ever had multiple tasks scheduled to run concurrently. Guarded by
   * `this`.
   */
  var isParallel = false

  /** Number of calls to [TaskRunner.Backend.execute]. Guarded by `this`. */
  var executeCallCount = 0

  /** Guarded by [taskRunner]. */
  var nanoTime = 0L
    private set

  /** Backlog of tasks to run. Only one task runs at a time. Guarded by `this`. */

  public <T> ListenableFuture<T> submit(Callable<T> task) {
    Preconditions.checkNotNull(task, "task must not be null!");
    return delegate.submit(task);
  }

  @Override
  public <T> ListenableFuture<T> submit(Runnable task, T result) {
    Preconditions.checkNotNull(task, "task must not be null!");
    Preconditions.checkNotNull(result, "result must not be null!");
    return delegate.submit(task, result);
  }

  @Override

  public <T> ListenableFuture<T> submit(Callable<T> task) {
    Preconditions.checkNotNull(task, "task must not be null!");
    return delegate.submit(task);
  }

  @Override
  public <T> ListenableFuture<T> submit(Runnable task, T result) {
    Preconditions.checkNotNull(task, "task must not be null!");
    Preconditions.checkNotNull(result, "result must not be null!");
    return delegate.submit(task, result);
  }

  @Override

       *   user task -- which means that we already got past this code (or else we exited early
       *   above))
       */
      // Unconditionally set; there is no risk of throwing away a queued task from another thread,
      // because in order for the current task to run on this executor the previous task must have
      // already started execution. Because each task on a TaskNonReentrantExecutor can only produce