title: When sessions are closed in mysql when creating a sqlalchemy session
body: <p>I still have sessions hibernating, although after creating the session, I closed it with both session.close() and session.remove().
  BUT mysql sessions in sleep state close them themselves after a random time</p>
  <p>I want to know:</p>
  <ol>
  <li>How to manage closing sessions</li>
  <li>Who closes sleep sessions</li>
  <li>Why close() and remove() don't work</li>
  </ol>