fix: support pool_pre_ping in SQLAlchemy ORM MySQL dialect

aws_advanced_python_wrapper/sqlalchemy/mysql_orm_dialect.py

@@ -77,6 +77,20 @@ def create_connect_args(self, url):
         # Return empty args list and kwargs dict
         return [], opts
 
+    def do_ping(self, dbapi_connection) -> bool:
+        """
+        Liveness check for SQLAlchemy's pool_pre_ping.
+        The parent pings dbapi_connection directly, but AwsWrapperConnection
+        has no ping(), so ping the wrapped driver connection instead.
+        Return False on the native error so the pool invalidates and reconnects;
+        SQLAlchemy cannot classify it because import_dbapi reports the wrapper as the DBAPI.
+        """
+        try:
+            dbapi_connection.target_connection.ping(reconnect=False)
+            return True
+        except Error:
+            return False
+
     def _detect_charset(self, connection: Connection) -> str:
         if isinstance(connection, CMySQLConnection):
             return connection.charset

tests/unit/test_mysql_orm_dialect.py

@@ -0,0 +1,43 @@
+#  Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+#  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.
+
+import pytest
+from mysql.connector.errors import OperationalError
+
+from aws_advanced_python_wrapper import AwsWrapperConnection
+from aws_advanced_python_wrapper.sqlalchemy.mysql_orm_dialect import \
+    SqlAlchemyOrmMysqlDialect
+
+
+@pytest.fixture
+def dialect():
+    # __init__ requires a live DBAPI, so bypass it to unit test do_ping in isolation.
+    return SqlAlchemyOrmMysqlDialect.__new__(SqlAlchemyOrmMysqlDialect)
+
+
+@pytest.fixture
+def dbapi_connection(mocker):
+    connection = mocker.MagicMock(spec=AwsWrapperConnection)
+    connection.target_connection = mocker.MagicMock()
+    return connection
+
+
+def test_do_ping_pings_wrapped_target_connection(dialect, dbapi_connection):
+    assert dialect.do_ping(dbapi_connection) is True
+    dbapi_connection.target_connection.ping.assert_called_once_with(reconnect=False)
+
+
+def test_do_ping_returns_false_on_dead_connection(dialect, dbapi_connection):
+    dbapi_connection.target_connection.ping.side_effect = OperationalError("MySQL server has gone away")
+    assert dialect.do_ping(dbapi_connection) is False