remove redundant checks and utilize new API

sky/serve/core.py

@@ -685,33 +685,26 @@ def sync_down_logs(service_name: str,
  service_component = serve_utils.ServiceComponent(service_component)
  if not isinstance(service_component, serve_utils.ServiceComponent):
  with ux_utils.print_exception_no_traceback():
- raise ValueError(
- f'`service_component` must be a string or '
- f'sky.serve.ServiceComponent, got {type(service_component)}.')
+ raise ValueError('`service_component` must be a string or '
+  'sky.serve.ServiceComponent, '
+  f'got {type(service_component)}.')
  if service_component == serve_utils.ServiceComponent.REPLICA:
  if replica_id is None:
  with ux_utils.print_exception_no_traceback():
  raise ValueError('`replica_id` must be specified when '
- 'using service_component=REPLICA.')
+  'using service_component=REPLICA.')
  else:
  if replica_id is not None:
  with ux_utils.print_exception_no_traceback():
- raise ValueError('`replica_id` must be None when using '
- 'service_component=CONTROLLER/LOAD_BALANCER.')
+ raise ValueError(
+ '`replica_id` must be None when using '
+ 'service_component=CONTROLLER/LOAD_BALANCER.')
 
  logger.info(f'Syncing down logs for {service_name}...')
  controller_handle = backend_utils.is_controller_accessible(
  controller=controller_utils.Controllers.SKY_SERVE_CONTROLLER,
  stopped_message='No service is found.')
 
- # Prepare logs for download.
- ssh_credentials = backend_utils.ssh_credential_from_yaml(
- controller_handle.cluster_yaml, controller_handle.docker_user)
- runner = command_runner.SSHCommandRunner(
- node=(controller_handle.head_ip, controller_handle.head_ssh_port),
- **ssh_credentials,
- )
-
  # Define local directory for logs and get the current timestamp.
  sky_logs_directory = os.path.expanduser(skylet_constants.SKY_LOGS_DIRECTORY)
  run_timestamp = backend_utils.get_run_timestamp()
@@ -741,6 +734,7 @@ def sync_down_logs(service_name: str,
  raise RuntimeError(e.error_msg) from e
 
  # Define remote directory for logs and download them.
+ runner = controller_handle.get_command_runners()
  remote_service_dir_name = (
  serve_utils.generate_remote_service_dir_name(service_name))
  dir_for_download = os.path.join(remote_service_dir_name, run_timestamp)
@@ -777,6 +771,7 @@ def sync_down_logs(service_name: str,
 
  if (sync_down_all_components or
  service_component == serve_utils.ServiceComponent.CONTROLLER):
+ runner = controller_handle.get_command_runners()
  controller_log_file_name = (
  serve_utils.generate_remote_controller_log_file_name(service_name))
  logger.info('Downloading the controller logs...')
@@ -793,6 +788,7 @@ def sync_down_logs(service_name: str,
 
  if (sync_down_all_components or
  service_component == serve_utils.ServiceComponent.LOAD_BALANCER):
+ runner = controller_handle.get_command_runners()
  load_balancer_log_file_name = (
  serve_utils.generate_remote_load_balancer_log_file_name(
  service_name))