Fix stale references in client routes handler

- Add type annotations to _ClientRoutesHandler.__init__
- Fix sleep() -> time.sleep()
- Fix dep -> cp variable name
- Add shutdown() method with _is_shutdown/_lock fields

Author: dkropachev

cassandra/client_routes.py

@@ -220,10 +220,12 @@ def __init__(self, config: 'ClientRoutesConfig', ssl_enabled: bool = False):
         if not isinstance(config, ClientRoutesConfig):
             raise TypeError("config must be a ClientRoutesConfig instance")
 
-        self.config = config
-        self.ssl_enabled = ssl_enabled
-        self._routes = _RouteStore()
-        self._initial_contact_points = {dep.connection_id for dep in config.contact_points}
+        self.config: ClientRoutesConfig = config
+        self.ssl_enabled: bool = ssl_enabled
+        self._routes: _RouteStore = _RouteStore()
+        self._initial_contact_points: Set[str] = {cp.connection_id for cp in config.contact_points}
+        self._is_shutdown: bool = False
+        self._lock = threading.RLock()
 
     def initialize(self, control_connection: 'ControlConnection') -> None:
         """
@@ -304,7 +306,7 @@ def handle_control_connection_reconnect(self, control_connection: 'ControlConnec
                 if attempt < max_attempts:
                     log.warning("[client routes] Transient failure reloading routes "
                                 "(attempt %d/%d): %s", attempt, max_attempts, e)
-                    sleep(1)
+                    time.sleep(1)
                 else:
                     log.error("[client routes] Failed to reload routes after %d attempts: %s",
                               max_attempts, e, exc_info=True)
@@ -395,3 +397,14 @@ def resolve_host(self, host_id: uuid.UUID) -> Optional[Tuple[str, int]]:
             return None
 
         return route.address, route.port
+
+    def shutdown(self) -> None:
+        """
+        Shutdown the handler and release resources.
+        """
+        with self._lock:
+            if self._is_shutdown:
+                return
+
+            self._is_shutdown = True
+            log.info("[client routes] Handler shutdown")