From 0f7e1b011024b19b5ec755cc3302032bc5a36008 Mon Sep 17 00:00:00 2001
From: Jib <jib.adegunloye@mongodb.com>
Date: Mon, 5 Feb 2024 08:46:32 -0500
Subject: [PATCH] PYTHON-4147: Silence noisy thread.start() RuntimeError at
 shutdown (#1486)

---
 doc/changelog.rst            |  3 +++
 pymongo/periodic_executor.py | 11 ++++++++++-
 test/test_monitor.py         | 12 ++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/doc/changelog.rst b/doc/changelog.rst
index c5fd8758dd..3feae4c2a4 100644
--- a/doc/changelog.rst
+++ b/doc/changelog.rst
@@ -29,6 +29,9 @@ PyMongo 4.7 brings a number of improvements including:
 
 .. _orjson: https://github.com/ijl/orjson
 
+- Fixed a bug appearing in Python 3.12 where "RuntimeError: can't create new thread at interpreter shutdown"
+  could be written to stderr when a MongoClient's thread starts as the python interpreter is shutting down.
+
 Changes in Version 4.6.1
 ------------------------
 
diff --git a/pymongo/periodic_executor.py b/pymongo/periodic_executor.py
index 25d519187f..9e9ead61fc 100644
--- a/pymongo/periodic_executor.py
+++ b/pymongo/periodic_executor.py
@@ -16,6 +16,7 @@
 
 from __future__ import annotations
 
+import sys
 import threading
 import time
 import weakref
@@ -91,7 +92,15 @@ 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().
diff --git a/test/test_monitor.py b/test/test_monitor.py
index 0495a8cbc7..8ccec7fd0b 100644
--- a/test/test_monitor.py
+++ b/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(
+            " ".join(command), shell=True, capture_output=True
+        )
+
+        self.assertFalse(completed_process.stderr)
+        self.assertFalse(completed_process.stdout)
+
 
 if __name__ == "__main__":
     unittest.main()