}
      }
    }
  }

  /**
   * Checks if the executor has been shut down and increments the running task count.
   *
   * @throws RejectedExecutionException if the executor has been previously shutdown
   */
  private void startTask() {
    synchronized (lock) {
      if (shutdown) {
        throw new RejectedExecutionException("Executor already shutdown");
      }
      runningTasks++;
    }
  }

Sometimes there's an action required like calling the application layer or responding to a ping, and the thread discovering the action is not the thread that should do the work. We enqueue a runnable on this executor and it gets handled by one of the executor's threads.

### Locks

We have 3 different things that we synchronize on.

#### Http2Connection

          @Override
          public String get(long time, TimeUnit unit) {
            return "foo"; // BAD!!
          }

          @Override
          public void addListener(Runnable runnable, Executor executor) {
            executor.execute(runnable);
          }
        };
    Future<?> future = newFutureInstance();
    future
        .getClass()
        .getMethod(
            "setFuture",

          @Override
          public String get(long time, TimeUnit unit) {
            return "foo"; // BAD!!
          }

          @Override
          public void addListener(Runnable runnable, Executor executor) {
            executor.execute(runnable);
          }
        };
    Future<?> future = newFutureInstance();
    future
        .getClass()
        .getMethod(
            "setFuture",

  ForwardingFluentFuture(ListenableFuture<V> delegate) {
    this.delegate = checkNotNull(delegate);
  }

  @Override
  public void addListener(Runnable listener, Executor executor) {
    delegate.addListener(listener, executor);
  }

  @Override
  public boolean cancel(boolean mayInterruptIfRunning) {
    return delegate.cancel(mayInterruptIfRunning);
  }

  @Override
  public boolean isCancelled() {

              @Override
              public Closeable call(DeferredCloser closer) throws Exception {
                return closer.eventuallyClose(mockCloseable, executor);
              }
            },
            executor);
    FluentFuture<Closeable> unused = closingFuture.finishToFuture();
    assertThrows(
        IllegalStateException.class,
        () -> {

   *
   * <p>RuntimeExceptions thrown by a listener will be caught and logged. Any exception thrown
   * during {@code Executor.execute} (e.g., a {@code RejectedExecutionException}) will be caught and
   * logged.
   *
   * @param listener the listener to run when the service changes state is complete
   * @param executor the executor in which the listeners callback methods will be run. For fast,

    return awaitTerminationUninterruptibly(executor, toNanosSaturated(timeout), NANOSECONDS);
  }

  /**
   * Invokes {@code executor.}{@link ExecutorService#awaitTermination(long, TimeUnit)
   * awaitTermination(long, TimeUnit)} uninterruptibly.
   *
   * @since 30.0
   */
  @J2ktIncompatible
  @GwtIncompatible // concurrency
  @SuppressWarnings("GoodTime")

      ListenableFuture<? extends V> input,
      Class<X> exceptionType,
      Function<? super X, ? extends V> fallback,
      Executor executor) {
    CatchingFuture<V, X> future = new CatchingFuture<>(input, exceptionType, fallback);
    input.addListener(future, rejectionPropagatingExecutor(executor, future));
    return future;
  }

  static <X extends Throwable, V extends @Nullable Object> ListenableFuture<V> createAsync(

   * calling thread. Tasks are run to completion before a {@code Future} is returned to the caller
   * (unless the executor has been shutdown).
   *
   * <p>The returned executor is backed by the executor returned by {@link
   * MoreExecutors#newDirectExecutorService} and subject to the same constraints.
   *