Synnefo » snf-ganeti

import time

class RunningTimeout(object):

  """Class to calculate remaining timeout when doing several operations.

  """

  __slots__ = [

    "_allow_negative",

    "_start_time",

    "_time_fn",

    "_timeout",

    ]

  def __init__(self, timeout, allow_negative, _time_fn=time.time):

    """Initializes this class.

    @type timeout: float

    @param timeout: Timeout duration

    @type allow_negative: bool

    @param allow_negative: Whether to return values below zero

    @param _time_fn: Time function for unittests

    """

    object.__init__(self)

    if timeout is not None and timeout < 0.0:

      raise ValueError("Timeout must not be negative")

    self._timeout = timeout

    self._allow_negative = allow_negative

    self._time_fn = _time_fn

    self._start_time = None

  def Remaining(self):

    """Returns the remaining timeout.

    """

    if self._timeout is None:

      return None

    # Get start time on first calculation

    if self._start_time is None:

      self._start_time = self._time_fn()

    # Calculate remaining time

    remaining_timeout = self._start_time + self._timeout - self._time_fn()

    if not self._allow_negative:

      # Ensure timeout is always >= 0

      return max(0.0, remaining_timeout)

    return remaining_timeout