neutron/tests/tempest/common/utils.py

# Copyright 2011, VMware, Inc.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
#
# Borrowed from nova code base, more utilities will be added/borrowed as and
# when needed.

"""Utilities and helper functions."""

import threading
import eventlet

class classproperty(object):
    def __init__(self, f):
        self.func = f

    def __get__(self, obj, owner):
	return self.func(owner)

class WaitTimeout(Exception):
    """Default exception coming from wait_until_true() function."""


class LockWithTimer(object):
    def __init__(self, threshold):
        self._threshold = threshold
        self.timestamp = 0
        self._lock = threading.Lock()

    def acquire(self):
        return self._lock.acquire(False)

    def release(self):
        return self._lock.release()

    def time_to_wait(self):
        return self.timestamp - time.time() + self._threshold

def wait_until_true(predicate, timeout=60, sleep=1, exception=None):
    """
    Wait until callable predicate is evaluated as True
    :param predicate: Callable deciding whether waiting should continue.
    Best practice is to instantiate predicate with functools.partial()
    :param timeout: Timeout in seconds how long should function wait.
    :param sleep: Polling interval for results in seconds.
    :param exception: Exception instance to raise on timeout. If None is passed
                      (default) then WaitTimeout exception is raised.
    """
    try:
        with eventlet.Timeout(timeout):
            while not predicate():
                eventlet.sleep(sleep)
    except eventlet.Timeout:
        if exception is not None:
            #pylint: disable=raising-bad-type
            raise exception
        raise WaitTimeout("Timed out after %d seconds" % timeout)