PYTHON-4537 - Use selector asyncio loop on windows tests

pymongo/asynchronous/periodic_executor.py

@@ -65,7 +65,17 @@ def __repr__(self) -> str:
         return f"<{self.__class__.__name__}(name={self._name}) object at 0x{id(self):x}>"
 
     def _run_async(self) -> None:
-        asyncio.run(self._run())  # type: ignore[func-returns-value]
+        # The default asyncio loop implementation on Windows
+        # has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
+        # We explicitly use a different loop implementation here to prevent that issue
+        if sys.platform == "win32":
+            loop = asyncio.SelectorEventLoop()
+            try:
+                loop.run_until_complete(self._run())  # type: ignore[func-returns-value]
+            finally:
+                loop.close()
+        else:
+            asyncio.run(self._run())  # type: ignore[func-returns-value]
 
     def open(self) -> None:
         """Start. Multiple calls have no effect.

pymongo/synchronous/periodic_executor.py

@@ -65,7 +65,17 @@ def __repr__(self) -> str:
         return f"<{self.__class__.__name__}(name={self._name}) object at 0x{id(self):x}>"
 
     def _run_async(self) -> None:
-        asyncio.run(self._run())  # type: ignore[func-returns-value]
+        # The default asyncio loop implementation on Windows
+        # has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
+        # We explicitly use a different loop implementation here to prevent that issue
+        if sys.platform == "win32":
+            loop = asyncio.SelectorEventLoop()
+            try:
+                loop.run_until_complete(self._run())  # type: ignore[func-returns-value]
+            finally:
+                loop.close()
+        else:
+            asyncio.run(self._run())  # type: ignore[func-returns-value]
 
     def open(self) -> None:
         """Start. Multiple calls have no effect.

test/__init__.py

@@ -79,6 +79,16 @@
 
 _IS_SYNC = True
 
+# The default asyncio loop implementation on Windows
+# has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
+# We explicitly use a different loop implementation here to prevent that issue
+if (
+    not _IS_SYNC
+    and sys.platform == "win32"
+    and asyncio.get_event_loop_policy() == asyncio.WindowsProactorEventLoopPolicy
+):
+    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())  # type: ignore[attr-defined]
+
 
 class ClientContext:
     client: MongoClient

test/asynchronous/__init__.py

@@ -79,6 +79,16 @@
 
 _IS_SYNC = False
 
+# The default asyncio loop implementation on Windows
+# has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
+# We explicitly use a different loop implementation here to prevent that issue
+if (
+    not _IS_SYNC
+    and sys.platform == "win32"
+    and asyncio.get_event_loop_policy() == asyncio.WindowsProactorEventLoopPolicy
+):
+    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())  # type: ignore[attr-defined]
+
 
 class AsyncClientContext:
     client: AsyncMongoClient