/* use AbstractService for state management */
  private final Service delegate =
      new AbstractService() {
        @Override
        protected final void doStart() {
          Executor executor = renamingDecorator(executor(), () -> serviceName());
          executor.execute(
              () -> {
                try {
                  startUp();
                  notifyStarted();

   *
   * @param identifier short name for the bus, for logging purposes.
   * @param executor Executor to use to dispatch events. It is the caller's responsibility to shut
   *     down the executor after the last event has been posted to this event bus.
   */
  public AsyncEventBus(String identifier, Executor executor) {
    super(identifier, executor, Dispatcher.legacyAsync(), LoggingHandler.INSTANCE);
  }

  /**

  /** Use {@link MoreExecutors#newSequentialExecutor} */
  SequentialExecutor(Executor executor) {
    this.executor = Preconditions.checkNotNull(executor);
  }

  /**
   * Adds a task to the queue and makes sure a worker thread is running.
   *
   * <p>If this method throws, e.g. a {@code RejectedExecutionException} from the delegate executor,
   * execution of tasks will stop until a call to this method is made.
   */

  /** Use {@link MoreExecutors#newSequentialExecutor} */
  SequentialExecutor(Executor executor) {
    this.executor = Preconditions.checkNotNull(executor);
  }

  /**
   * Adds a task to the queue and makes sure a worker thread is running.
   *
   * <p>If this method throws, e.g. a {@code RejectedExecutionException} from the delegate executor,
   * execution of tasks will stop until a call to this method is made.
   */

{* ../../docs_src/background_tasks/tutorial001_py39.py hl[14] *}

`.add_task()` recibe como argumentos:

* Una función de tarea para ejecutar en segundo plano (`write_notification`).
* Cualquier secuencia de argumentos que deba pasarse a la función de tarea en orden (`email`).

  }

  /**
   * Adds a listener that will be called using the given executor when events are later {@link
   * #enqueue enqueued} and {@link #dispatch dispatched}.
   */
  public void addListener(L listener, Executor executor) {
    checkNotNull(listener, "listener");
    checkNotNull(executor, "executor");
    listeners.add(new PerListenerQueue<>(listener, executor));
  }

  /**

   */
  public <T extends @Nullable Object> ListenableFuture<T> submitAsync(
      AsyncCallable<T> callable, Executor executor) {
    checkNotNull(callable);
    checkNotNull(executor);
    TaskNonReentrantExecutor taskExecutor = new TaskNonReentrantExecutor(executor, this);
    AsyncCallable<T> task =
        new AsyncCallable<T>() {
          @Override

   */
  public static <K, V> RemovalListener<K, V> asynchronous(
      RemovalListener<K, V> listener, Executor executor) {
    checkNotNull(listener);
    checkNotNull(executor);
    return (RemovalNotification<K, V> notification) ->
        executor.execute(() -> listener.onRemoval(notification));
  }

    )

  fun connectionCount(): Int = connectionCount.get()

  fun shutdown() {
    serverSocket!!.close()
    executor.shutdown()
    if (!executor.awaitTermination(5, TimeUnit.SECONDS)) {
      throw IOException("Gave up waiting for executor to shut down")
    }
  }

  private fun service(from: Socket) {
    val name = "SocksProxy ${from.remoteSocketAddress}"
    threadName(name) {

    barrier.await(1, SECONDS);
    assertFalse(executor.isShutdown());
    assertFalse(executor.isTerminated());

    executor.shutdown();
    assertTrue(executor.isShutdown());
    assertThrows(RejectedExecutionException.class, () -> executor.submit(() -> {}));
    assertFalse(executor.isTerminated());

    // WAIT #2
    barrier.await(1, SECONDS);
    assertFalse(executor.awaitTermination(20, MILLISECONDS));