title: Is the whole job restarted if one task fails
body: <p>I have a job that has stateful operators and has also enabled checkpointing. One of the tasks of the staful operator fails due to some reason and has be restarted and recover the checkpointed state.</p>
  <p>I would ask which of the followings is the restart behavor:</p>
  <ol>
  <li>only the failed task is restarted and restored</li>
  <li>all of the operator(contain failed task)'s tasks are restarted and restored</li>
  <li>the whole job is restarted and restored</li>
  </ol>