PYTHON-4147 [v4.6]: Silence noisy thread.start() RuntimeError at shut…

…down (#1532)

Co-authored-by: Jib <jib.adegunloye@mongodb.com>

pymongo/periodic_executor.py

@@ -16,6 +16,7 @@
 
 from __future__ import annotations
 
+import sys
 import threading
 import time
 import weakref
@@ -92,7 +93,15 @@ def open(self) -> None:
             thread.daemon = True
             self._thread = weakref.proxy(thread)
             _register_executor(self)
-            thread.start()
+            # Mitigation to RuntimeError firing when thread starts on shutdown
+            # https://github.com/python/cpython/issues/114570
+            try:
+                thread.start()
+            except RuntimeError as e:
+                if "interpreter shutdown" in str(e) or sys.is_finalizing():
+                    self._thread = None
+                    return
+                raise
 
     def close(self, dummy: Any = None) -> None:
         """Stop. To restart, call open().

test/test_monitor.py

@@ -16,6 +16,7 @@
 from __future__ import annotations
 
 import gc
+import subprocess
 import sys
 from functools import partial
 
@@ -79,6 +80,17 @@ def test_cleanup_executors_on_client_close(self):
         for executor in executors:
             wait_until(lambda: executor._stopped, f"closed executor: {executor._name}", timeout=5)
 
+    def test_no_thread_start_runtime_err_on_shutdown(self):
+        """Test we silence noisy runtime errors fired when the MongoClient spawns a new thread
+        on process shutdown."""
+        command = [sys.executable, "-c", "from pymongo import MongoClient; c = MongoClient()"]
+        completed_process: subprocess.CompletedProcess = subprocess.run(
+            command, capture_output=True
+        )
+
+        self.assertFalse(completed_process.stderr)
+        self.assertFalse(completed_process.stdout)
+
 
 if __name__ == "__main__":
     unittest.main()