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# Copyright 2016 OpenMarket Ltd
#
# 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.
from twisted.internet import defer
from twisted.internet.defer import Deferred
from synapse.util.async_helpers import ReadWriteLock
from tests import unittest
class ReadWriteLockTestCase(unittest.TestCase):
def _assert_called_before_not_after(self, lst, first_false):
for i, d in enumerate(lst[:first_false]):
self.assertTrue(d.called, msg="%d was unexpectedly false" % i)
for i, d in enumerate(lst[first_false:]):
self.assertFalse(
d.called, msg="%d was unexpectedly true" % (i + first_false)
)
def test_rwlock(self):
rwlock = ReadWriteLock()
key = object()
ds = [
rwlock.read(key), # 0
rwlock.read(key), # 1
rwlock.write(key), # 2
rwlock.write(key), # 3
rwlock.read(key), # 4
rwlock.read(key), # 5
rwlock.write(key), # 6
]
ds = [defer.ensureDeferred(d) for d in ds]
self._assert_called_before_not_after(ds, 2)
with ds[0].result:
self._assert_called_before_not_after(ds, 2)
self._assert_called_before_not_after(ds, 2)
with ds[1].result:
self._assert_called_before_not_after(ds, 2)
self._assert_called_before_not_after(ds, 3)
with ds[2].result:
self._assert_called_before_not_after(ds, 3)
self._assert_called_before_not_after(ds, 4)
with ds[3].result:
self._assert_called_before_not_after(ds, 4)
self._assert_called_before_not_after(ds, 6)
with ds[5].result:
self._assert_called_before_not_after(ds, 6)
self._assert_called_before_not_after(ds, 6)
with ds[4].result:
self._assert_called_before_not_after(ds, 6)
self._assert_called_before_not_after(ds, 7)
with ds[6].result:
pass
d = defer.ensureDeferred(rwlock.write(key))
self.assertTrue(d.called)
with d.result:
pass
d = defer.ensureDeferred(rwlock.read(key))
self.assertTrue(d.called)
with d.result:
pass
def test_lock_handoff_to_nonblocking_writer(self):
"""Test a writer handing the lock to another writer that completes instantly."""
rwlock = ReadWriteLock()
key = "key"
unblock: "Deferred[None]" = Deferred()
async def blocking_write():
with await rwlock.write(key):
await unblock
async def nonblocking_write():
with await rwlock.write(key):
pass
d1 = defer.ensureDeferred(blocking_write())
d2 = defer.ensureDeferred(nonblocking_write())
self.assertFalse(d1.called)
self.assertFalse(d2.called)
# Unblock the first writer. The second writer will complete without blocking.
unblock.callback(None)
self.assertTrue(d1.called)
self.assertTrue(d2.called)
# The `ReadWriteLock` should operate as normal.
d3 = defer.ensureDeferred(nonblocking_write())
self.assertTrue(d3.called)
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