chore: stabilize MySQL tests by aligning isolation levels (#28028)

tests/integration_tests/charts/data/api_tests.py

@@ -21,6 +21,7 @@ import unittest
 import copy
 from datetime import datetime
 from io import BytesIO
+import time
 from typing import Any, Optional
 from unittest import mock
 from zipfile import ZipFile
@@ -723,8 +724,12 @@ class TestPostChartDataApi(BaseTestChartDataApi):
         app._got_first_request = False
         async_query_manager_factory.init_app(app)
         self.login(ADMIN_USERNAME)
+        # Introducing time.sleep to make test less flaky with MySQL
+        time.sleep(1)
         rv = self.post_assert_metric(CHART_DATA_URI, self.query_context_payload, "data")
+        time.sleep(1)
         self.assertEqual(rv.status_code, 202)
+        time.sleep(1)
         data = json.loads(rv.data.decode("utf-8"))
         keys = list(data.keys())
         self.assertCountEqual(