PYTHON-5218 - Add logging statement when SRV polling fails (#2463)

Co-authored-by: Jib <Jibzade@gmail.com>

Author: NoahStapp

pymongo/asynchronous/monitor.py

@@ -423,12 +423,13 @@ async def _get_seedlist(self) -> Optional[list[tuple[str, Any]]]:
             if len(seedlist) == 0:
                 # As per the spec: this should be treated as a failure.
                 raise Exception
-        except Exception:
+        except Exception as exc:
             # As per the spec, upon encountering an error:
             # - An error must not be raised
             # - SRV records must be rescanned every heartbeatFrequencyMS
             # - Topology must be left unchanged
             self.request_check()
+            _debug_log(_SDAM_LOGGER, message="SRV monitor check failed", failure=repr(exc))
             return None
         else:
             self._executor.update_interval(max(ttl, common.MIN_SRV_RESCAN_INTERVAL))

pymongo/synchronous/monitor.py

@@ -421,12 +421,13 @@ def _get_seedlist(self) -> Optional[list[tuple[str, Any]]]:
             if len(seedlist) == 0:
                 # As per the spec: this should be treated as a failure.
                 raise Exception
-        except Exception:
+        except Exception as exc:
             # As per the spec, upon encountering an error:
             # - An error must not be raised
             # - SRV records must be rescanned every heartbeatFrequencyMS
             # - Topology must be left unchanged
             self.request_check()
+            _debug_log(_SDAM_LOGGER, message="SRV monitor check failed", failure=repr(exc))
             return None
         else:
             self._executor.update_interval(max(ttl, common.MIN_SRV_RESCAN_INTERVAL))

test/asynchronous/test_srv_polling.py

@@ -225,6 +225,19 @@ def response_callback(*args):
 
             await self.run_scenario(response_callback, False)
 
+    async def test_dns_failures_logging(self):
+        from dns import exception
+
+        with self.assertLogs("pymongo.topology", level="DEBUG") as cm:
+
+            def response_callback(*args):
+                raise exception.Timeout("DNS Failure!")
+
+            await self.run_scenario(response_callback, False)
+
+        srv_failure_logs = [r for r in cm.records if "SRV monitor check failed" in r.getMessage()]
+        self.assertEqual(len(srv_failure_logs), 1)
+
     async def test_dns_record_lookup_empty(self):
         response: list = []
         await self.run_scenario(response, False)

test/test_srv_polling.py

@@ -225,6 +225,19 @@ def response_callback(*args):
 
             self.run_scenario(response_callback, False)
 
+    def test_dns_failures_logging(self):
+        from dns import exception
+
+        with self.assertLogs("pymongo.topology", level="DEBUG") as cm:
+
+            def response_callback(*args):
+                raise exception.Timeout("DNS Failure!")
+
+            self.run_scenario(response_callback, False)
+
+        srv_failure_logs = [r for r in cm.records if "SRV monitor check failed" in r.getMessage()]
+        self.assertEqual(len(srv_failure_logs), 1)
+
     def test_dns_record_lookup_empty(self):
         response: list = []
         self.run_scenario(response, False)