Browse Source

Make memoize behave better in concurrent environments

Currently there is a chance for System view to raise sqlite3
exceptions because of table lock in PersistentDict.

1) Stop re-loading content on PersistentDict creation.
2) Retry OperationalError on all database accesses.
3) Rule out a race condition in __delitem__

Also refactor tests to remove excessive mocking.

Change-Id: I82726c41578700835f3b15d316aed562d68fbf67
changes/33/765333/1
Dmitry Tantsur 10 months ago
parent
commit
8d52482c79
  1. 1
      lower-constraints.txt
  2. 1
      requirements.txt
  3. 35
      sushy_tools/emulator/memoize.py
  4. 154
      sushy_tools/tests/unit/emulator/test_memoize.py

1
lower-constraints.txt

@ -55,6 +55,7 @@ Sphinx==2.0.0
sphinxcontrib-websupport==1.0.1
stestr==1.0.0
stevedore==1.20.0
tenacity==6.2.0
testrepository==0.0.20
testscenarios==0.4
testtools==2.2.0

1
requirements.txt

@ -5,3 +5,4 @@
pbr!=2.1.0,>=2.0.0 # Apache-2.0
Flask>=1.0.2 # BSD
requests>=2.14.2 # Apache-2.0
tenacity>=6.2.0 # Apache-2.0

35
sushy_tools/emulator/memoize.py

@ -26,6 +26,8 @@ import pickle
import sqlite3
import tempfile
import tenacity
# Python 3.8
MutableMapping = getattr(collections, 'abc', collections).MutableMapping
@ -71,6 +73,13 @@ def memoize(permanent_cache=None):
return decorator
_retry = tenacity.retry(
retry=tenacity.retry_if_exception_type(sqlite3.OperationalError),
wait=tenacity.wait_exponential(min=0.1, max=2, multiplier=1),
stop=tenacity.stop_after_delay(5),
reraise=True)
class PersistentDict(MutableMapping):
DBPATH = os.path.join(tempfile.gettempdir(), 'sushy-emulator')
@ -88,8 +97,6 @@ class PersistentDict(MutableMapping):
'(key blob primary key not null, value blob not null)'
)
self.update(dict(self))
@staticmethod
def encode(obj):
return pickle.dumps(obj)
@ -103,16 +110,10 @@ class PersistentDict(MutableMapping):
if not self._dbpath:
raise TypeError('Dict is not yet persistent')
connection = sqlite3.connect(self._dbpath)
try:
with sqlite3.connect(self._dbpath) as connection:
yield connection.cursor()
connection.commit()
finally:
connection.close()
@_retry
def __getitem__(self, key):
key = self.encode(key)
@ -128,6 +129,7 @@ class PersistentDict(MutableMapping):
return self.decode(value[0])
@_retry
def __setitem__(self, key, value):
key = self.encode(key)
value = self.encode(value)
@ -138,23 +140,19 @@ class PersistentDict(MutableMapping):
(key, value)
)
@_retry
def __delitem__(self, key):
key = self.encode(key)
with self.connection() as cursor:
cursor.execute(
'select count(*) from cache where key=?',
(key,)
)
if cursor.fetchone()[0] == 0:
raise KeyError(key)
cursor.execute(
'delete from cache where key=?',
(key,)
)
if not cursor.rowcount:
raise KeyError(key)
@_retry
def __iter__(self):
with self.connection() as cursor:
cursor.execute(
@ -165,6 +163,7 @@ class PersistentDict(MutableMapping):
for r in records:
yield self.decode(r[0])
@_retry
def __len__(self):
with self.connection() as cursor:
cursor.execute(

154
sushy_tools/tests/unit/emulator/test_memoize.py

@ -12,6 +12,9 @@
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import pickle
import sqlite3
from unittest import mock
from oslotest import base
@ -82,112 +85,145 @@ class MemoizeTestCase(base.BaseTestCase):
self.assertEqual(0, driver.call_count)
@mock.patch.object(sqlite3, 'connect', autospec=True)
class PersistentDictTestCase(base.BaseTestCase):
@mock.patch.object(memoize, 'sqlite3', autospec=True)
def test_make_permanent(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_sqlite3.assert_called_once_with('/file.sqlite')
mock_sqlite3.connect.assert_called_with('/file.sqlite')
@mock.patch.object(memoize, 'pickle', autospec=True)
def test_encode(self, mock_pickle):
def test_encode(self, mock_sqlite3):
pd = memoize.PersistentDict()
value = pd.encode({1: '2'})
self.assertEqual(pickle.dumps({1: '2'}), value)
pd.encode({1: '2'})
mock_pickle.dumps.assert_called_once_with({1: '2'})
def test_decode(self, mock_sqlite3):
pd = memoize.PersistentDict()
value = pd.decode(pickle.dumps({1: '2'}))
self.assertEqual({1: '2'}, value)
@mock.patch.object(memoize, 'pickle', autospec=True)
def test_decode(self, mock_pickle):
def test___getitem__(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
pd.decode('blob')
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
mock_cursor.fetchone.return_value = [pickle.dumps('pickled-value')]
mock_pickle.loads.assert_called_once_with('blob')
result = pd[1]
self.assertEqual('pickled-value', result)
@mock.patch.object(memoize, 'pickle', autospec=True)
@mock.patch.object(memoize, 'sqlite3', autospec=True)
def test___getitem__(self, mock_sqlite3, mock_pickle):
mock_cursor.execute.assert_called_with(
'select value from cache where key=?', (pickle.dumps(1),))
def test___getitem__retries(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_pickle.dumps.return_value = 'pickled-key'
mock_connection = mock_sqlite3.connect.return_value
mock_cursor = mock_connection.cursor.return_value
mock_cursor.fetchone.return_value = ['pickled-value']
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
mock_cursor.execute.side_effect = [
sqlite3.OperationalError,
None
]
mock_cursor.fetchone.return_value = [pickle.dumps('pickled-value')]
pd[1]
result = pd[1]
self.assertEqual('pickled-value', result)
mock_cursor.execute.assert_called_with(
'select value from cache where key=?', ('pickled-key',))
mock_pickle.loads.assert_called_once_with('pickled-value')
'select value from cache where key=?', (pickle.dumps(1),))
self.assertEqual(2, mock_cursor.execute.call_count)
@mock.patch.object(memoize, 'pickle', autospec=True)
@mock.patch.object(memoize, 'sqlite3', autospec=True)
def test___setitem__(self, mock_sqlite3, mock_pickle):
def test___setitem__(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_pickle.dumps.side_effect = [
'pickled-key', 'pickled-value']
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
mock_connection = mock_sqlite3.connect.return_value
mock_cursor = mock_connection.cursor.return_value
pd[1] = 2
mock_cursor.execute.assert_called_once_with(
'insert or replace into cache values (?, ?)',
(pickle.dumps(1), pickle.dumps(2)))
def test___setitem__retries(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
mock_cursor.execute.side_effect = [
sqlite3.OperationalError,
None
]
pd[1] = 2
mock_cursor.execute.assert_called_with(
'insert or replace into cache values (?, ?)',
('pickled-key', 'pickled-value'))
(pickle.dumps(1), pickle.dumps(2)))
self.assertEqual(2, mock_cursor.execute.call_count)
@mock.patch.object(memoize, 'pickle', autospec=True)
@mock.patch.object(memoize, 'sqlite3', autospec=True)
def test___delitem__(self, mock_sqlite3, mock_pickle):
def test___delitem__(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_pickle.dumps.return_value = 'pickled-key'
mock_connection = mock_sqlite3.connect.return_value
mock_cursor = mock_connection.cursor.return_value
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
del pd[1]
mock_cursor.execute.assert_called_with(
'delete from cache where key=?', ('pickled-key',))
mock_cursor.execute.assert_called_once_with(
'delete from cache where key=?', (pickle.dumps(1),))
@mock.patch.object(memoize, 'pickle', autospec=True)
@mock.patch.object(memoize, 'sqlite3', autospec=True)
def test___iter__(self, mock_sqlite3, mock_pickle):
def test___delitem__fails(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_pickle.dumps.return_value = 'pickled-key'
mock_connection = mock_sqlite3.connect.return_value
mock_cursor = mock_connection.cursor.return_value
mock_cursor.fetchall.return_value = [['pickled-key']]
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
mock_cursor.rowcount = 0
for x in pd:
x += x
def _del():
del pd[1]
mock_cursor.execute.assert_called_with('select key from cache')
mock_pickle.loads.assert_called_once_with('pickled-key')
self.assertRaises(KeyError, _del)
@mock.patch.object(memoize, 'pickle', autospec=True)
@mock.patch.object(memoize, 'sqlite3', autospec=True)
def test___len__(self, mock_sqlite3, mock_pickle):
mock_cursor.execute.assert_called_once_with(
'delete from cache where key=?', (pickle.dumps(1),))
def test___iter__(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_connection = mock_sqlite3.connect.return_value
mock_cursor = mock_connection.cursor.return_value
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
mock_cursor.fetchall.return_value = [[pickle.dumps('pickled-key')]]
self.assertEqual(['pickled-key'], list(iter(pd)))
mock_cursor.execute.assert_called_once_with('select key from cache')
expected = 1
def test___len__(self, mock_sqlite3):
pd = memoize.PersistentDict()
pd.make_permanent('/', 'file')
mock_cursor.fetchone.return_value = [expected]
mock_conn = mock_sqlite3.return_value.__enter__.return_value
mock_cursor = mock_conn.cursor.return_value
mock_cursor.execute.reset_mock()
mock_cursor.fetchone.return_value = [42]
self.assertEqual(expected, len(pd))
self.assertEqual(42, len(pd))
mock_cursor.execute.assert_called_with('select count(*) from cache')
mock_cursor.execute.assert_called_once_with(
'select count(*) from cache')
Loading…
Cancel
Save