cluster: use dynamic whitelist policy for proxy access

cassandra/client_routes.py

@@ -294,7 +294,7 @@ def handle_client_routes_change(self, connection: 'Connection', timeout: float,
             return
 
         routes = self._query_routes_for_change_event(connection, timeout, pairs)
-        self._routes.merge(routes, affected_host_ids=set(host_uuids))
+        self._routes.merge(routes, affected_host_ids={host_id for _, host_id in pairs})
 
     def _query_all_routes_for_connections(self, connection: 'Connection', timeout: float,
                                           connection_ids: Set[str]) -> List[_Route]:
@@ -322,27 +322,25 @@ def _query_all_routes_for_connections(self, connection: 'Connection', timeout: f
     def _query_routes_for_change_event(self, connection: 'Connection', timeout: float,
                                        route_pairs: List[Tuple[str, uuid.UUID]]) -> List[_Route]:
         """
-        Query specific routes affected by a CLIENT_ROUTES_CHANGE event.
+        Query current routes for hosts affected by a CLIENT_ROUTES_CHANGE event.
 
-        Takes a list of (connection_id, host_id) pairs that represent the exact
-        routes affected by an operation. This provides precise updates without
-        fetching unrelated routes.
-
-        If the pairs list is empty or None, falls back to a complete refresh
-        of all routes for safety.
+        The in-memory route store keeps a single preferred route per host. When
+        any configured connection_id changes for a host, fetch all configured
+        connection_ids for that host so the existing preferred route can be
+        retained if it is still present.
 
         :param connection: Connection to execute query on
         :param timeout: Query timeout in seconds
-        :param route_pairs: List of (connection_id, host_id) tuples
+        :param route_pairs: List of affected (connection_id, host_id) tuples
         :return: List of _Route
         """
         unique_pairs = list(dict.fromkeys(route_pairs))
 
-        conn_ids = list(dict.fromkeys(cid for cid, _ in unique_pairs))
+        conn_ids = sorted(self._connection_ids)
         host_ids = list(dict.fromkeys(hid for _, hid in unique_pairs))
 
-        log.debug("[client routes] Querying route pairs from CLIENT_ROUTES_CHANGE "
-                  "(first 5 of %d): %s", len(unique_pairs), unique_pairs[:5])
+        log.debug("[client routes] Querying routes from CLIENT_ROUTES_CHANGE "
+                  "for host_ids (first 5 of %d): %s", len(host_ids), host_ids[:5])
 
         conn_ph = ', '.join('?' for _ in conn_ids)
         host_ph = ', '.join('?' for _ in host_ids)