Add tests for database transaction callbacks (#12198)

Signed-off-by: Sean Quah <seanq@element.io>
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Sean Quah 2022-03-15 15:40:34 +00:00 committed by GitHub
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2 changed files with 104 additions and 1 deletions

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changelog.d/12198.misc Normal file
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Add tests for database transaction callbacks.

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@ -12,7 +12,18 @@
# See the License for the specific language governing permissions and
# limitations under the License.
from synapse.storage.database import make_tuple_comparison_clause
from typing import Callable, Tuple
from unittest.mock import Mock, call
from twisted.test.proto_helpers import MemoryReactor
from synapse.server import HomeServer
from synapse.storage.database import (
DatabasePool,
LoggingTransaction,
make_tuple_comparison_clause,
)
from synapse.util import Clock
from tests import unittest
@ -22,3 +33,94 @@ class TupleComparisonClauseTestCase(unittest.TestCase):
clause, args = make_tuple_comparison_clause([("a", 1), ("b", 2)])
self.assertEqual(clause, "(a,b) > (?,?)")
self.assertEqual(args, [1, 2])
class CallbacksTestCase(unittest.HomeserverTestCase):
"""Tests for transaction callbacks."""
def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
self.store = hs.get_datastores().main
self.db_pool: DatabasePool = self.store.db_pool
def _run_interaction(
self, func: Callable[[LoggingTransaction], object]
) -> Tuple[Mock, Mock]:
"""Run the given function in a database transaction, with callbacks registered.
Args:
func: The function to be run in a transaction. The transaction will be
retried if `func` raises an `OperationalError`.
Returns:
Two mocks, which were registered as an `after_callback` and an
`exception_callback` respectively, on every transaction attempt.
"""
after_callback = Mock()
exception_callback = Mock()
def _test_txn(txn: LoggingTransaction) -> None:
txn.call_after(after_callback, 123, 456, extra=789)
txn.call_on_exception(exception_callback, 987, 654, extra=321)
func(txn)
try:
self.get_success_or_raise(
self.db_pool.runInteraction("test_transaction", _test_txn)
)
except Exception:
pass
return after_callback, exception_callback
def test_after_callback(self) -> None:
"""Test that the after callback is called when a transaction succeeds."""
after_callback, exception_callback = self._run_interaction(lambda txn: None)
after_callback.assert_called_once_with(123, 456, extra=789)
exception_callback.assert_not_called()
def test_exception_callback(self) -> None:
"""Test that the exception callback is called when a transaction fails."""
_test_txn = Mock(side_effect=ZeroDivisionError)
after_callback, exception_callback = self._run_interaction(_test_txn)
after_callback.assert_not_called()
exception_callback.assert_called_once_with(987, 654, extra=321)
def test_failed_retry(self) -> None:
"""Test that the exception callback is called for every failed attempt."""
# Always raise an `OperationalError`.
_test_txn = Mock(side_effect=self.db_pool.engine.module.OperationalError)
after_callback, exception_callback = self._run_interaction(_test_txn)
after_callback.assert_not_called()
exception_callback.assert_has_calls(
[
call(987, 654, extra=321),
call(987, 654, extra=321),
call(987, 654, extra=321),
call(987, 654, extra=321),
call(987, 654, extra=321),
call(987, 654, extra=321),
]
)
self.assertEqual(exception_callback.call_count, 6) # no additional calls
def test_successful_retry(self) -> None:
"""Test callbacks for a failed transaction followed by a successful attempt."""
# Raise an `OperationalError` on the first attempt only.
_test_txn = Mock(
side_effect=[self.db_pool.engine.module.OperationalError, None]
)
after_callback, exception_callback = self._run_interaction(_test_txn)
# Calling both `after_callback`s when the first attempt failed is rather
# surprising (#12184). Let's document the behaviour in a test.
after_callback.assert_has_calls(
[
call(123, 456, extra=789),
call(123, 456, extra=789),
]
)
self.assertEqual(after_callback.call_count, 2) # no additional calls
exception_callback.assert_not_called()