code: public void shutdown(final String taskId, String reasonFormat, Object... args)
    {
      giant.lock();
  
      try {
        Preconditions.checkNotNull(taskId, "taskId");
        for (final Task task : tasks) {
          if (task.getId().equals(taskId)) {
            notifyStatus(task, TaskStatus.failure(taskId), reasonFormat, args);
            break;
          }
        }
      }
      finally {
        giant.unlock();
      }
    }
docs: Shuts down a task if it has not yet finished.
  
  @param taskId task to kill