PYTHON-3027 Fix server selection when topology type is Unknown

pymongo/topology_description.py

@@ -263,9 +263,10 @@ def apply_selector(self, selector, address=None, custom_selector=None):
                                              selector.min_wire_version,
                                              common_wv))
 
-        if self.topology_type in (TOPOLOGY_TYPE.Single,
-                                  TOPOLOGY_TYPE.LoadBalanced,
-                                  TOPOLOGY_TYPE.Unknown):
+        if self.topology_type == TOPOLOGY_TYPE.Unknown:
+            return []
+        elif self.topology_type in (TOPOLOGY_TYPE.Single,
+                                    TOPOLOGY_TYPE.LoadBalanced):
             # Ignore selectors for standalone and load balancer mode.
             return self.known_servers
         elif address:

test/mockupdb/test_rsghost.py

@@ -0,0 +1,52 @@
+# Copyright 2021-present MongoDB, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Test connections to RSGhost nodes."""
+
+import datetime
+
+from mockupdb import going, MockupDB
+from pymongo import MongoClient
+from pymongo.errors import ServerSelectionTimeoutError
+
+import unittest
+
+
+class TestRSGhost(unittest.TestCase):
+
+    def test_rsghost(self):
+        rsother_response = {
+            'ok': 1.0, 'ismaster': False, 'secondary': False,
+            'info': 'Does not have a valid replica set config',
+            'isreplicaset': True, 'maxBsonObjectSize': 16777216,
+            'maxMessageSizeBytes': 48000000, 'maxWriteBatchSize': 100000,
+            'localTime': datetime.datetime(2021, 11, 30, 0, 53, 4, 99000),
+            'logicalSessionTimeoutMinutes': 30, 'connectionId': 3,
+            'minWireVersion': 0, 'maxWireVersion': 15, 'readOnly': False}
+        server = MockupDB(auto_ismaster=rsother_response)
+        server.run()
+        self.addCleanup(server.stop)
+        # Default auto discovery yields a server selection timeout.
+        with MongoClient(server.uri, serverSelectionTimeoutMS=250) as client:
+            with self.assertRaises(ServerSelectionTimeoutError):
+                client.test.command('ping')
+        # Direct connection succeeds.
+        with MongoClient(server.uri, directConnection=True) as client:
+            with going(client.test.command, 'ping'):
+                request = server.receives(ping=1)
+                request.reply()
+
+
+if __name__ == '__main__':
+    unittest.main()

test/server_selection/server_selection/Unknown/read/ghost.json

@@ -0,0 +1,18 @@
+{
+  "topology_description": {
+    "type": "Unknown",
+    "servers": [
+      {
+        "address": "a:27017",
+        "avg_rtt_ms": 5,
+        "type": "RSGhost"
+      }
+    ]
+  },
+  "operation": "read",
+  "read_preference": {
+    "mode": "Nearest"
+  },
+  "suitable_servers": [],
+  "in_latency_window": []
+}

test/server_selection/server_selection/Unknown/write/ghost.json

@@ -0,0 +1,18 @@
+{
+  "topology_description": {
+    "type": "Unknown",
+    "servers": [
+      {
+        "address": "a:27017",
+        "avg_rtt_ms": 5,
+        "type": "RSGhost"
+      }
+    ]
+  },
+  "operation": "write",
+  "read_preference": {
+    "mode": "Nearest"
+  },
+  "suitable_servers": [],
+  "in_latency_window": []
+}

test/utils_selection_tests.py

@@ -63,7 +63,7 @@ def make_server_description(server, hosts):
         return ServerDescription(clean_node(server['address']), Hello({}))
 
     hello_response = {'ok': True, 'hosts': hosts}
-    if server_type != "Standalone" and server_type != "Mongos":
+    if server_type not in ("Standalone", "Mongos", "RSGhost"):
         hello_response['setName'] = "rs"
 
     if server_type == "RSPrimary":
@@ -72,6 +72,10 @@ def make_server_description(server, hosts):
         hello_response['secondary'] = True
     elif server_type == "Mongos":
         hello_response['msg'] = 'isdbgrid'
+    elif server_type == "RSGhost":
+        hello_response['isreplicaset'] = True
+    elif server_type == "RSArbiter":
+        hello_response['arbiterOnly'] = True
 
     hello_response['lastWrite'] = {
         'lastWriteDate': make_last_write_date(server)
@@ -149,7 +153,7 @@ def create_topology(scenario_def, **kwargs):
 
     # Assert that descriptions match
     assert (scenario_def['topology_description']['type'] ==
-           topology.description.topology_type_name)
+           topology.description.topology_type_name), topology.description.topology_type_name
 
     return topology