baseimage-tutorial-framework/lib/tfw/builtins/frontend_event_handler.py

from tfw.networking import Scope
from tfw.components import FrontendMessageStorage

from .event_handler import EventHandler


class FrontendEventHandler(EventHandler):
    def __init__(self):
        frontend_keys = ('message', 'queueMessages', 'dashboard', 'console')
        self._frontend_message_storage = FrontendMessageStorage(frontend_keys)
        super().__init__((*frontend_keys, 'recover'), scope=Scope.WEBSOCKET)

    def handle_event(self, message):
        self._frontend_message_storage.save_message(message)
        if message['key'] == 'recover':
            self.recover_frontend()
        self.send_message(message)

    def recover_frontend(self):
        for message in self._frontend_message_storage.messages:
            self.send_message(message)