mirror of
https://github.com/avatao-content/baseimage-tutorial-framework
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71 lines
2.4 KiB
Python
71 lines
2.4 KiB
Python
import logging
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from tfw.crypto import KeyManager, sign_message, verify_message
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from tfw.networking import Scope
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from tfw.components import FSMUpdater
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LOG = logging.getLogger(__name__)
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class FSMManagingEventHandler:
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keys = ['fsm']
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"""
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EventHandler responsible for managing the state machine of
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the framework (TFW FSM).
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tfw.networking.TFWServer instances automatically send 'trigger'
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commands to the event handler listening on the 'fsm' key,
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which should be an instance of this event handler.
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This event handler accepts messages that have a
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data['command'] key specifying a command to be executed.
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An 'fsm_update' message is broadcasted after every successful
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command.
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"""
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def __init__(self, *, fsm_type, require_signature=False):
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self.fsm = fsm_type()
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self._fsm_updater = FSMUpdater(self.fsm)
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self.auth_key = KeyManager().auth_key
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self._require_signature = require_signature
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self.command_handlers = {
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'trigger': self.handle_trigger,
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'update': self.handle_update
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}
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def handle_event(self, message, server_connector):
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try:
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message = self.command_handlers[message['data']['command']](message)
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if message:
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fsm_update_message = self._fsm_updater.fsm_update
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sign_message(self.auth_key, message)
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sign_message(self.auth_key, fsm_update_message)
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server_connector.send_message(fsm_update_message, Scope.BROADCAST)
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except KeyError:
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LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)
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def handle_trigger(self, message):
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"""
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Attempts to step the FSM with the supplied trigger.
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:param message: TFW message with a data field containing
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the action to try triggering in data['value']
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"""
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trigger = message['data']['value']
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if self._require_signature:
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if not verify_message(self.auth_key, message):
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LOG.error('Ignoring unsigned trigger command: %s', message)
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return None
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if self.fsm.step(trigger):
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return message
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return None
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def handle_update(self, message):
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"""
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Does nothing, but triggers an 'fsm_update' message.
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"""
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# pylint: disable=no-self-use
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return message
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