Tornado exit from a gen.sleep()

I want to exit from an existing gen.sleep state. USer will send a HTTP POST with a param to trigger this method.

I use a Tornado loop to start a process which refresh some authentication/tokens every 30 minutes. In some situations user revoke access but app is still in sleep state hence I want to restart workflow.

Example:

async def _loop(self):
    """Refresh logic."""
    while self.state() == "ACTIVE":     
      if self.auth_enabled():
        try:
          password = await _get_metadata()
          if password:
            _store_password(password)
        except Exception as e
          logger.exception(e)     
        await gen.sleep(retry_secs)
      else:
        logger.info("sleeping...")
        # Break pause here.
        await gen.sleep(SLEEP_SECS)

Class

class RefreshPassword:
 def __init__(self):
   self._event = locks.Event()

 def start(self):
    if self.state() != "ACTIVE":
      self._state = "ACTIVE":
      self._event.clear()
      ioloop.IOLoop.current().add_callback(self._loop)
      return

 def stop(self):
    if self.state() == "ACTIVE":
      self._state = "STOPPED"
      self._event.set()

 

class PasswordHandler(web.RequestHandler):
  """Handles HTTP requests"""

  SUPPORTED_METHODS = ["GET", "POST"]

  def init(self, calendar: RefreshPassword):
    """Initializes RefreshPassword calendar object.

    Args:
      calendar(RefreshPassword): Keeps Password updated.
    """
    self._calendar = calendar
  
  async def post(self):
    if self._calendar.state() == "ACTIVE":
      try:
        restart = self.get_argument("restart", default="false")
        if restart.lower() == "true":
          logger.info("Stopping refresh process")
          self._calendar.stop()
        else:
          logger.warning(msg)
          self.set_status(409)
          self.write(msg)
          self.finish()
          return
      except web.MissingArgumentError as exc:
        logger.exception(exc)
    # Initialize workflow
    self._calendar.start()
    self.set_status(201)
    self.write(msg)
    self.finish()    

I have tried the following, but tornado gets blocked on sleep.

async def _wait(self):
    done, _ = await asyncio.wait(
        [gen.sleep(SLEEP_SECS), self._event],
        return_when=asyncio.FIRST_COMPLETED,
    )
    logger.info("Wait done: %s", done)
    if self._event.is_set():
      logger.info("Wait interrupted")
      self._event.clear()
    else:
      logger.info("Wait completed")

  async def _refresh(self):
    # Wait for the collection of any task to be completed.
    # This allows restarting workflow when we are waiting for refresh.
    # If self._event is completed, exit and interrupt sleep event.
    ioloop.IOLoop.current().add_callback(self._wait)

That's not a good design. You need to queue up a callback in N seconds, which allows you to return to the main loop so it can continue processing. You can't do sleeps. You must return, just like in a GUI application.

You can use ioloop.IOLoop.current().add_timeout to request a callback after a period of time.