Sync to spec

Author: NoahStapp

pymongo/topology_description.py

@@ -352,13 +352,26 @@ def apply_selector(
                     if custom_selector:
                         sds = custom_selector(sds)
                     return sds
+            # All primaries are deprioritized
+            if deprioritized_servers:
+                for sd in deprioritized_servers:
+                    if sd.server_type == SERVER_TYPE.RSPrimary:
+                        sds = [sd]
+                        if custom_selector:
+                            sds = custom_selector(sds)
+                        return sds
             # No primary found, return an empty list.
             return []
 
         selection = Selection.from_topology_description(self)
         # Ignore read preference for sharded clusters.
         if self.topology_type != TOPOLOGY_TYPE.Sharded:
             selection = selector(selection)
+            # No suitable servers found, apply preference again but include deprioritized servers.
+            if not selection and deprioritized_servers:
+                self._filter_servers(None)
+                selection = Selection.from_topology_description(self)
+                selection = selector(selection)
 
         # Apply custom selector followed by localThresholdMS.
         if custom_selector is not None and selection:

test/server_selection/server_selection/ReplicaSetWithPrimary/read/DeprioritizedPrimary.json

@@ -43,7 +43,23 @@
     }
   ],
   "suitable_servers": [
+    {
+      "address": "a:27017",
+      "avg_rtt_ms": 5,
+      "type": "RSPrimary",
+      "tags": {
+        "data_center": "nyc"
+      }
+    }
   ],
   "in_latency_window": [
+    {
+      "address": "a:27017",
+      "avg_rtt_ms": 5,
+      "type": "RSPrimary",
+      "tags": {
+        "data_center": "nyc"
+      }
+    }
   ]
 }

test/server_selection/server_selection/ReplicaSetWithPrimary/read/DeprioritizedSecondary.json

@@ -56,7 +56,31 @@
     }
   ],
   "suitable_servers": [
+    {
+      "address": "b:27017",
+      "avg_rtt_ms": 5,
+      "type": "RSSecondary",
+      "tags": {
+        "data_center": "nyc"
+      }
+    },
+    {
+      "address": "c:27017",
+      "avg_rtt_ms": 100,
+      "type": "RSSecondary",
+      "tags": {
+        "data_center": "nyc"
+      }
+    }
   ],
   "in_latency_window": [
+    {
+      "address": "b:27017",
+      "avg_rtt_ms": 5,
+      "type": "RSSecondary",
+      "tags": {
+        "data_center": "nyc"
+      }
+    }
   ]
 }

test/server_selection/server_selection/ReplicaSetWithPrimary/write/DeprioritizedSecondaryPreferred.json

@@ -48,7 +48,23 @@
     }
   ],
   "suitable_servers": [
+    {
+      "address": "a:27017",
+      "avg_rtt_ms": 26,
+      "type": "RSPrimary",
+      "tags": {
+        "data_center": "nyc"
+      }
+    }
   ],
   "in_latency_window": [
+    {
+      "address": "a:27017",
+      "avg_rtt_ms": 26,
+      "type": "RSPrimary",
+      "tags": {
+        "data_center": "nyc"
+      }
+    }
   ]
 }