diff options
Diffstat (limited to 'tests')
| -rw-r--r-- | tests/util/test_rwlock.py | 395 |
1 files changed, 337 insertions, 58 deletions
diff --git a/tests/util/test_rwlock.py b/tests/util/test_rwlock.py index 0774625b85..0c84226197 100644 --- a/tests/util/test_rwlock.py +++ b/tests/util/test_rwlock.py @@ -12,8 +12,10 @@ # See the License for the specific language governing permissions and # limitations under the License. +from typing import AsyncContextManager, Callable, Sequence, Tuple + from twisted.internet import defer -from twisted.internet.defer import Deferred +from twisted.internet.defer import CancelledError, Deferred from synapse.util.async_helpers import ReadWriteLock @@ -21,87 +23,187 @@ 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) + def _start_reader_or_writer( + self, + read_or_write: Callable[[str], AsyncContextManager], + key: str, + return_value: str, + ) -> Tuple["Deferred[str]", "Deferred[None]", "Deferred[None]"]: + """Starts a reader or writer which acquires the lock, blocks, then completes. + + Args: + read_or_write: A function returning a context manager for a lock. + Either a bound `ReadWriteLock.read` or `ReadWriteLock.write`. + key: The key to read or write. + return_value: A string that the reader or writer will resolve with when + done. + + Returns: + A tuple of three `Deferred`s: + * A `Deferred` that resolves with `return_value` once the reader or writer + completes successfully. + * A `Deferred` that resolves once the reader or writer acquires the lock. + * A `Deferred` that blocks the reader or writer. Must be resolved by the + caller to allow the reader or writer to release the lock and complete. + """ + acquired_d: "Deferred[None]" = Deferred() + unblock_d: "Deferred[None]" = Deferred() + + async def reader_or_writer(): + async with read_or_write(key): + acquired_d.callback(None) + await unblock_d + return return_value + + d = defer.ensureDeferred(reader_or_writer()) + return d, acquired_d, unblock_d + + def _start_blocking_reader( + self, rwlock: ReadWriteLock, key: str, return_value: str + ) -> Tuple["Deferred[str]", "Deferred[None]", "Deferred[None]"]: + """Starts a reader which acquires the lock, blocks, then releases the lock. + + See the docstring for `_start_reader_or_writer` for details about the arguments + and return values. + """ + return self._start_reader_or_writer(rwlock.read, key, return_value) + + def _start_blocking_writer( + self, rwlock: ReadWriteLock, key: str, return_value: str + ) -> Tuple["Deferred[str]", "Deferred[None]", "Deferred[None]"]: + """Starts a writer which acquires the lock, blocks, then releases the lock. + + See the docstring for `_start_reader_or_writer` for details about the arguments + and return values. + """ + return self._start_reader_or_writer(rwlock.write, key, return_value) + + def _start_nonblocking_reader( + self, rwlock: ReadWriteLock, key: str, return_value: str + ) -> Tuple["Deferred[str]", "Deferred[None]"]: + """Starts a reader which acquires the lock, then releases it immediately. + + See the docstring for `_start_reader_or_writer` for details about the arguments. + + Returns: + A tuple of two `Deferred`s: + * A `Deferred` that resolves with `return_value` once the reader completes + successfully. + * A `Deferred` that resolves once the reader acquires the lock. + """ + d, acquired_d, unblock_d = self._start_reader_or_writer( + rwlock.read, key, return_value + ) + unblock_d.callback(None) + return d, acquired_d + + def _start_nonblocking_writer( + self, rwlock: ReadWriteLock, key: str, return_value: str + ) -> Tuple["Deferred[str]", "Deferred[None]"]: + """Starts a writer which acquires the lock, then releases it immediately. + + See the docstring for `_start_reader_or_writer` for details about the arguments. + + Returns: + A tuple of two `Deferred`s: + * A `Deferred` that resolves with `return_value` once the writer completes + successfully. + * A `Deferred` that resolves once the writer acquires the lock. + """ + d, acquired_d, unblock_d = self._start_reader_or_writer( + rwlock.write, key, return_value + ) + unblock_d.callback(None) + return d, acquired_d + + def _assert_first_n_resolved( + self, deferreds: Sequence["defer.Deferred[None]"], n: int + ) -> None: + """Assert that exactly the first n `Deferred`s in the given list are resolved. - for i, d in enumerate(lst[first_false:]): + Args: + deferreds: The list of `Deferred`s to be checked. + n: The number of `Deferred`s at the start of `deferreds` that should be + resolved. + """ + for i, d in enumerate(deferreds[:n]): + self.assertTrue(d.called, msg="deferred %d was unexpectedly unresolved" % i) + + for i, d in enumerate(deferreds[n:]): self.assertFalse( - d.called, msg="%d was unexpectedly true" % (i + first_false) + d.called, msg="deferred %d was unexpectedly resolved" % (i + n) ) def test_rwlock(self): rwlock = ReadWriteLock() - - key = object() + key = "key" 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 + self._start_blocking_reader(rwlock, key, "0"), + self._start_blocking_reader(rwlock, key, "1"), + self._start_blocking_writer(rwlock, key, "2"), + self._start_blocking_writer(rwlock, key, "3"), + self._start_blocking_reader(rwlock, key, "4"), + self._start_blocking_reader(rwlock, key, "5"), + self._start_blocking_writer(rwlock, key, "6"), ] - ds = [defer.ensureDeferred(d) for d in ds] + # `Deferred`s that resolve when each reader or writer acquires the lock. + acquired_ds = [acquired_d for _, acquired_d, _ in ds] + # `Deferred`s that will trigger the release of locks when resolved. + release_ds = [release_d for _, _, release_d in ds] - self._assert_called_before_not_after(ds, 2) + # The first two readers should acquire their locks. + self._assert_first_n_resolved(acquired_ds, 2) - with ds[0].result: - self._assert_called_before_not_after(ds, 2) - self._assert_called_before_not_after(ds, 2) + # Release one of the read locks. The next writer should not acquire the lock, + # because there is another reader holding the lock. + self._assert_first_n_resolved(acquired_ds, 2) + release_ds[0].callback(None) + self._assert_first_n_resolved(acquired_ds, 2) - with ds[1].result: - self._assert_called_before_not_after(ds, 2) - self._assert_called_before_not_after(ds, 3) + # Release the other read lock. The next writer should acquire the lock. + self._assert_first_n_resolved(acquired_ds, 2) + release_ds[1].callback(None) + self._assert_first_n_resolved(acquired_ds, 3) - with ds[2].result: - self._assert_called_before_not_after(ds, 3) - self._assert_called_before_not_after(ds, 4) + # Release the write lock. The next writer should acquire the lock. + self._assert_first_n_resolved(acquired_ds, 3) + release_ds[2].callback(None) + self._assert_first_n_resolved(acquired_ds, 4) - with ds[3].result: - self._assert_called_before_not_after(ds, 4) - self._assert_called_before_not_after(ds, 6) + # Release the write lock. The next two readers should acquire locks. + self._assert_first_n_resolved(acquired_ds, 4) + release_ds[3].callback(None) + self._assert_first_n_resolved(acquired_ds, 6) - with ds[5].result: - self._assert_called_before_not_after(ds, 6) - self._assert_called_before_not_after(ds, 6) + # Release one of the read locks. The next writer should not acquire the lock, + # because there is another reader holding the lock. + self._assert_first_n_resolved(acquired_ds, 6) + release_ds[5].callback(None) + self._assert_first_n_resolved(acquired_ds, 6) - with ds[4].result: - self._assert_called_before_not_after(ds, 6) - self._assert_called_before_not_after(ds, 7) + # Release the other read lock. The next writer should acquire the lock. + self._assert_first_n_resolved(acquired_ds, 6) + release_ds[4].callback(None) + self._assert_first_n_resolved(acquired_ds, 7) - with ds[6].result: - pass + # Release the write lock. + release_ds[6].callback(None) - d = defer.ensureDeferred(rwlock.write(key)) - self.assertTrue(d.called) - with d.result: - pass + # Acquire and release the write and read locks one last time for good measure. + _, acquired_d = self._start_nonblocking_writer(rwlock, key, "last writer") + self.assertTrue(acquired_d.called) - d = defer.ensureDeferred(rwlock.read(key)) - self.assertTrue(d.called) - with d.result: - pass + _, acquired_d = self._start_nonblocking_reader(rwlock, key, "last reader") + self.assertTrue(acquired_d.called) 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()) + d1, _, unblock = self._start_blocking_writer(rwlock, key, "write 1 completed") + d2, _ = self._start_nonblocking_writer(rwlock, key, "write 2 completed") self.assertFalse(d1.called) self.assertFalse(d2.called) @@ -111,5 +213,182 @@ class ReadWriteLockTestCase(unittest.TestCase): self.assertTrue(d2.called) # The `ReadWriteLock` should operate as normal. - d3 = defer.ensureDeferred(nonblocking_write()) + d3, _ = self._start_nonblocking_writer(rwlock, key, "write 3 completed") self.assertTrue(d3.called) + + def test_cancellation_while_holding_read_lock(self): + """Test cancellation while holding a read lock. + + A waiting writer should be given the lock when the reader holding the lock is + cancelled. + """ + rwlock = ReadWriteLock() + key = "key" + + # 1. A reader takes the lock and blocks. + reader_d, _, _ = self._start_blocking_reader(rwlock, key, "read completed") + + # 2. A writer waits for the reader to complete. + writer_d, _ = self._start_nonblocking_writer(rwlock, key, "write completed") + self.assertFalse(writer_d.called) + + # 3. The reader is cancelled. + reader_d.cancel() + self.failureResultOf(reader_d, CancelledError) + + # 4. The writer should take the lock and complete. + self.assertTrue( + writer_d.called, "Writer is stuck waiting for a cancelled reader" + ) + self.assertEqual("write completed", self.successResultOf(writer_d)) + + def test_cancellation_while_holding_write_lock(self): + """Test cancellation while holding a write lock. + + A waiting reader should be given the lock when the writer holding the lock is + cancelled. + """ + rwlock = ReadWriteLock() + key = "key" + + # 1. A writer takes the lock and blocks. + writer_d, _, _ = self._start_blocking_writer(rwlock, key, "write completed") + + # 2. A reader waits for the writer to complete. + reader_d, _ = self._start_nonblocking_reader(rwlock, key, "read completed") + self.assertFalse(reader_d.called) + + # 3. The writer is cancelled. + writer_d.cancel() + self.failureResultOf(writer_d, CancelledError) + + # 4. The reader should take the lock and complete. + self.assertTrue( + reader_d.called, "Reader is stuck waiting for a cancelled writer" + ) + self.assertEqual("read completed", self.successResultOf(reader_d)) + + def test_cancellation_while_waiting_for_read_lock(self): + """Test cancellation while waiting for a read lock. + + Tests that cancelling a waiting reader: + * does not cancel the writer it is waiting on + * does not cancel the next writer waiting on it + * does not allow the next writer to acquire the lock before an earlier writer + has finished + * does not keep the next writer waiting indefinitely + + These correspond to the asserts with explicit messages. + """ + rwlock = ReadWriteLock() + key = "key" + + # 1. A writer takes the lock and blocks. + writer1_d, _, unblock_writer1 = self._start_blocking_writer( + rwlock, key, "write 1 completed" + ) + + # 2. A reader waits for the first writer to complete. + # This reader will be cancelled later. + reader_d, _ = self._start_nonblocking_reader(rwlock, key, "read completed") + self.assertFalse(reader_d.called) + + # 3. A second writer waits for both the first writer and the reader to complete. + writer2_d, _ = self._start_nonblocking_writer(rwlock, key, "write 2 completed") + self.assertFalse(writer2_d.called) + + # 4. The waiting reader is cancelled. + # Neither of the writers should be cancelled. + # The second writer should still be waiting, but only on the first writer. + reader_d.cancel() + self.failureResultOf(reader_d, CancelledError) + self.assertFalse(writer1_d.called, "First writer was unexpectedly cancelled") + self.assertFalse( + writer2_d.called, + "Second writer was unexpectedly cancelled or given the lock before the " + "first writer finished", + ) + + # 5. Unblock the first writer, which should complete. + unblock_writer1.callback(None) + self.assertEqual("write 1 completed", self.successResultOf(writer1_d)) + + # 6. The second writer should take the lock and complete. + self.assertTrue( + writer2_d.called, "Second writer is stuck waiting for a cancelled reader" + ) + self.assertEqual("write 2 completed", self.successResultOf(writer2_d)) + + def test_cancellation_while_waiting_for_write_lock(self): + """Test cancellation while waiting for a write lock. + + Tests that cancelling a waiting writer: + * does not cancel the reader or writer it is waiting on + * does not cancel the next writer waiting on it + * does not allow the next writer to acquire the lock before an earlier reader + and writer have finished + * does not keep the next writer waiting indefinitely + + These correspond to the asserts with explicit messages. + """ + rwlock = ReadWriteLock() + key = "key" + + # 1. A reader takes the lock and blocks. + reader_d, _, unblock_reader = self._start_blocking_reader( + rwlock, key, "read completed" + ) + + # 2. A writer waits for the reader to complete. + writer1_d, _, unblock_writer1 = self._start_blocking_writer( + rwlock, key, "write 1 completed" + ) + + # 3. A second writer waits for both the reader and first writer to complete. + # This writer will be cancelled later. + writer2_d, _ = self._start_nonblocking_writer(rwlock, key, "write 2 completed") + self.assertFalse(writer2_d.called) + + # 4. A third writer waits for the second writer to complete. + writer3_d, _ = self._start_nonblocking_writer(rwlock, key, "write 3 completed") + self.assertFalse(writer3_d.called) + + # 5. The second writer is cancelled, but continues waiting for the lock. + # The reader, first writer and third writer should not be cancelled. + # The first writer should still be waiting on the reader. + # The third writer should still be waiting on the second writer. + writer2_d.cancel() + self.assertNoResult(writer2_d) + self.assertFalse(reader_d.called, "Reader was unexpectedly cancelled") + self.assertFalse(writer1_d.called, "First writer was unexpectedly cancelled") + self.assertFalse( + writer3_d.called, + "Third writer was unexpectedly cancelled or given the lock before the first " + "writer finished", + ) + + # 6. Unblock the reader, which should complete. + # The first writer should be given the lock and block. + # The third writer should still be waiting on the second writer. + unblock_reader.callback(None) + self.assertEqual("read completed", self.successResultOf(reader_d)) + self.assertNoResult(writer2_d) + self.assertFalse( + writer3_d.called, + "Third writer was unexpectedly given the lock before the first writer " + "finished", + ) + + # 7. Unblock the first writer, which should complete. + unblock_writer1.callback(None) + self.assertEqual("write 1 completed", self.successResultOf(writer1_d)) + + # 8. The second writer should take the lock and release it immediately, since it + # has been cancelled. + self.failureResultOf(writer2_d, CancelledError) + + # 9. The third writer should take the lock and complete. + self.assertTrue( + writer3_d.called, "Third writer is stuck waiting for a cancelled writer" + ) + self.assertEqual("write 3 completed", self.successResultOf(writer3_d)) |