Ensure polling thread is resilient to errors and exceptions (#60)

* Ensure polling thread is resilient to API errors

* Ensure polling thread is resilient to request exceptions

* Use proper logger

* Remove intermediate mocks

* Prefer mocker fixture

* Remove unecessary return_value with side_effect

---------

Co-authored-by: Kim Gustyr <[email protected]>

Author: goncalossilva

flagsmith/polling_manager.py

@@ -1,10 +1,17 @@
+import logging
 import threading
 import time
 import typing
 
+import requests
+
+from flagsmith.exceptions import FlagsmithAPIError
+
 if typing.TYPE_CHECKING:
     from flagsmith import Flagsmith
 
+logger = logging.getLogger(__name__)
+
 
 class EnvironmentDataPollingManager(threading.Thread):
     def __init__(
@@ -21,7 +28,10 @@ def __init__(
 
     def run(self) -> None:
         while not self._stop_event.is_set():
-            self.main.update_environment()
+            try:
+                self.main.update_environment()
+            except (FlagsmithAPIError, requests.RequestException):
+                logger.exception("Failed to update environment")
             time.sleep(self.refresh_interval_seconds)
 
     def stop(self) -> None:

tests/test_polling_manager.py

@@ -1,6 +1,9 @@
 import time
 from unittest import mock
 
+import requests
+
+from flagsmith import Flagsmith
 from flagsmith.polling_manager import EnvironmentDataPollingManager
 
 
@@ -35,3 +38,35 @@ def test_polling_manager_calls_update_environment_on_each_refresh():
     # for each subsequent refresh
     assert flagsmith.update_environment.call_count == 3
     polling_manager.stop()
+
+
+def test_polling_manager_is_resilient_to_api_errors(mocker, server_api_key):
+    # Given
+    session_mock = mocker.patch("requests.Session")
+    session_mock.get.return_value = mock.MagicMock(status_code=500)
+    flagsmith = Flagsmith(
+        environment_key=server_api_key,
+        enable_local_evaluation=True,
+        environment_refresh_interval_seconds=0.1,
+    )
+    polling_manager = flagsmith.environment_data_polling_manager_thread
+
+    # Then
+    assert polling_manager.is_alive()
+    polling_manager.stop()
+
+
+def test_polling_manager_is_resilient_to_request_exceptions(mocker, server_api_key):
+    # Given
+    session_mock = mocker.patch("requests.Session")
+    session_mock.get.side_effect = requests.RequestException()
+    flagsmith = Flagsmith(
+        environment_key=server_api_key,
+        enable_local_evaluation=True,
+        environment_refresh_interval_seconds=0.1,
+    )
+    polling_manager = flagsmith.environment_data_polling_manager_thread
+
+    # Then
+    assert polling_manager.is_alive()
+    polling_manager.stop()