PYTHON-5202 WaitQueueTimeoutError should not clear the pool (#2192) [v4.11] (#2196)

Co-authored-by: Shane Harvey <shnhrv@gmail.com>

pymongo/asynchronous/topology.py

@@ -40,6 +40,7 @@ from pymongo.errors import (
     OperationFailure,
     PyMongoError,
     ServerSelectionTimeoutError,
+    WaitQueueTimeoutError,
     WriteError,
 )
 from pymongo.hello import Hello
@@ -877,6 +878,8 @@ class Topology:
                 # Clear the pool.
                 await server.reset(service_id)
         elif isinstance(error, ConnectionFailure):
+            if isinstance(error, WaitQueueTimeoutError):
+                return
             # "Client MUST replace the server's description with type Unknown
             # ... MUST NOT request an immediate check of the server."
             if not self._settings.load_balanced:

pymongo/synchronous/topology.py

@@ -36,6 +36,7 @@ from pymongo.errors import (
     OperationFailure,
     PyMongoError,
     ServerSelectionTimeoutError,
+    WaitQueueTimeoutError,
     WriteError,
 )
 from pymongo.hello import Hello
@@ -875,6 +876,8 @@ class Topology:
                 # Clear the pool.
                 server.reset(service_id)
         elif isinstance(error, ConnectionFailure):
+            if isinstance(error, WaitQueueTimeoutError):
+                return
             # "Client MUST replace the server's description with type Unknown
             # ... MUST NOT request an immediate check of the server."
             if not self._settings.load_balanced:

test/asynchronous/test_client.py

@@ -111,6 +111,7 @@ from pymongo.errors import (
     NetworkTimeout,
     OperationFailure,
     ServerSelectionTimeoutError,
+    WaitQueueTimeoutError,
     WriteConcernError,
 )
 from pymongo.monitoring import ServerHeartbeatListener, ServerHeartbeatStartedEvent
@@ -1311,8 +1312,16 @@ class TestClient(AsyncIntegrationTest):
         self.assertAlmostEqual(30, client.options.server_selection_timeout)
 
     async def test_waitQueueTimeoutMS(self):
-        client = await self.async_rs_or_single_client(waitQueueTimeoutMS=2000)
-        self.assertEqual((await async_get_pool(client)).opts.wait_queue_timeout, 2)
+        listener = CMAPListener()
+        client = await self.async_rs_or_single_client(
+            waitQueueTimeoutMS=10, maxPoolSize=1, event_listeners=[listener]
+        )
+        pool = await async_get_pool(client)
+        self.assertEqual(pool.opts.wait_queue_timeout, 0.01)
+        async with pool.checkout():
+            with self.assertRaises(WaitQueueTimeoutError):
+                await client.test.command("ping")
+        self.assertFalse(listener.events_by_type(monitoring.PoolClearedEvent))
 
     async def test_socketKeepAlive(self):
         pool = await async_get_pool(self.client)

test/test_client.py

@@ -100,6 +100,7 @@ from pymongo.errors import (
     NetworkTimeout,
     OperationFailure,
     ServerSelectionTimeoutError,
+    WaitQueueTimeoutError,
     WriteConcernError,
 )
 from pymongo.monitoring import ServerHeartbeatListener, ServerHeartbeatStartedEvent
@@ -1270,8 +1271,16 @@ class TestClient(IntegrationTest):
         self.assertAlmostEqual(30, client.options.server_selection_timeout)
 
     def test_waitQueueTimeoutMS(self):
-        client = self.rs_or_single_client(waitQueueTimeoutMS=2000)
-        self.assertEqual((get_pool(client)).opts.wait_queue_timeout, 2)
+        listener = CMAPListener()
+        client = self.rs_or_single_client(
+            waitQueueTimeoutMS=10, maxPoolSize=1, event_listeners=[listener]
+        )
+        pool = get_pool(client)
+        self.assertEqual(pool.opts.wait_queue_timeout, 0.01)
+        with pool.checkout():
+            with self.assertRaises(WaitQueueTimeoutError):
+                client.test.command("ping")
+        self.assertFalse(listener.events_by_type(monitoring.PoolClearedEvent))
 
     def test_socketKeepAlive(self):
         pool = get_pool(self.client)