UUID sentinel

Add a private _UUIDSentinels() class to oslo_utils.fixture that behaves
like a mock.sentinel, but returns specifically UUIDs. Expose a
(singleton) instance of it called uuidsentinel. This is mostly copied
from [1], with the following differences:

- We don't do the enforced-singleton thing [2]. But importing the
  uuidsentinel global yields the same behavior.
- We don't do the local import thing [3][4], because we're already in
  the right lib, so no issues with circular imports.
- Locking is added to make this threadsafe. (See discussion at [5])

Note that there is some question as to whether it is more appropriate
for this to live here or in oslotest [6]. This has been discussed on the
dev ML [7] and it was concluded [8] that it should live here.

[1] 722d5b4772/nova/tests/uuidsentinel.py
[2] 722d5b4772/nova/tests/uuidsentinel.py (L30)
[3] 722d5b4772/nova/tests/uuidsentinel.py (L18-L19)
[4] 722d5b4772/nova/tests/uuidsentinel.py (L26)
[5] http://eavesdrop.openstack.org/irclogs/%23openstack-oslo/%23openstack-oslo.2018-08-20.log.html#t2018-08-20T20:10:33
[6] https://review.openstack.org/#/c/594068/
[7] http://lists.openstack.org/pipermail/openstack-dev/2018-August/133670.html
[8] http://lists.openstack.org/pipermail/openstack-dev/2018-August/133861.html

Change-Id: I214ff21b461fa1ca4b83476e1d0a763efe986217
This commit is contained in:
Eric Fried 2018-08-21 08:00:54 -05:00
parent e49586e458
commit 63d7649ed5
2 changed files with 62 additions and 0 deletions

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@ -20,9 +20,12 @@ Test fixtures.
.. versionadded:: 1.3
"""
import threading
import fixtures
from oslo_utils import timeutils
from oslo_utils import uuidutils
class TimeFixture(fixtures.Fixture):
@ -49,3 +52,41 @@ class TimeFixture(fixtures.Fixture):
def advance_time_seconds(self, seconds):
"""Advance overridden time by seconds."""
timeutils.advance_time_seconds(seconds)
class _UUIDSentinels(object):
"""Registry of dynamically created, named, random UUID strings.
An instance of this class will dynamically generate attributes as they are
referenced, associating a random UUID string with each. Thereafter,
referring to the same attribute will give the same UUID for the life of the
instance. Plan accordingly.
Usage:
from oslo_utils.fixture import uuidsentinel as uuids
...
foo = uuids.foo
do_a_thing(foo)
# Referencing the same sentinel again gives the same value
assert foo == uuids.foo
# But a different one will be different
assert foo != uuids.bar
"""
def __init__(self):
self._sentinels = {}
self._lock = threading.Lock()
def __getattr__(self, name):
if name.startswith('_'):
raise ValueError('Sentinels must not start with _')
with self._lock:
if name not in self._sentinels:
self._sentinels[name] = uuidutils.generate_uuid()
return self._sentinels[name]
# Singleton sentinel instance. Caveat emptor: using this multiple times in the
# same process (including across multiple modules) will result in the same
# values
uuidsentinel = _UUIDSentinels()

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@ -17,9 +17,12 @@
import datetime
from oslotest import base as test_base
import six
from oslo_utils import fixture
from oslo_utils.fixture import uuidsentinel as uuids
from oslo_utils import timeutils
from oslo_utils import uuidutils
class TimeFixtureTest(test_base.BaseTestCase):
@ -61,3 +64,21 @@ class TimeFixtureTest(test_base.BaseTestCase):
time_fixture.advance_time_seconds(2)
expected_time = datetime.datetime(2015, 1, 2, 3, 4, 8, 7)
self.assertEqual(expected_time, timeutils.utcnow())
class UUIDSentinelsTest(test_base.BaseTestCase):
def test_different_sentinel(self):
uuid1 = uuids.foobar
uuid2 = uuids.barfoo
self.assertNotEqual(uuid1, uuid2)
def test_returns_uuid(self):
self.assertTrue(uuidutils.is_uuid_like(uuids.foo))
def test_returns_string(self):
self.assertIsInstance(uuids.foo, str)
def test_with_underline_prefix(self):
ex = self.assertRaises(ValueError, getattr, uuids, '_foo')
self.assertIn("Sentinels must not start with _", six.text_type(ex))