mirror of
https://github.com/avatao-content/baseimage-tutorial-framework
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133 lines
3.8 KiB
Python
133 lines
3.8 KiB
Python
# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
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# All Rights Reserved. See LICENSE file for details.
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import logging
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from abc import ABC, abstractmethod
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from inspect import currentframe
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from typing import Iterable
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from .tfw_server_connector import TFWServerConnector
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LOG = logging.getLogger(__name__)
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class EventHandlerBase(ABC):
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"""
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Abstract base class for all Python based EventHandlers. Useful implementation template
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for other languages.
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Derived classes must implement the handle_event() method
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"""
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def __init__(self, key):
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self.server_connector = TFWServerConnector()
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self.keys = []
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if isinstance(key, str):
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self.keys.append(key)
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elif isinstance(key, Iterable):
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self.keys = list(key)
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self.subscribe(*self.keys)
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self.server_connector.register_callback(self.event_handler_callback)
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@property
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def key(self):
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"""
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Returns the oldest key this EventHandler was subscribed to.
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"""
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return self.keys[0]
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def event_handler_callback(self, message):
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"""
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Callback that is invoked when receiving a message.
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Dispatches messages to handler methods and sends
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a response back in case the handler returned something.
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This is subscribed in __init__().
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"""
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if not self.check_key(message):
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return
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response = self.dispatch_handling(message)
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if response:
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self.send_message(response)
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def send_message(self, message):
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self.server_connector.send_message(message)
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def check_key(self, message):
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"""
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Checks whether the message is intended for this
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EventHandler.
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This is necessary because ZMQ handles PUB - SUB
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connetions with pattern matching (e.g. someone
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subscribed to 'fsm' will receive 'fsm_update'
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messages as well.
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"""
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if '' in self.keys:
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return True
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return message['key'] in self.keys
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def dispatch_handling(self, message):
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"""
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Used to dispatch messages to their specific handlers.
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:param message: the message received
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:returns: the message to send back
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"""
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return self.handle_event(message)
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@abstractmethod
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def handle_event(self, message):
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"""
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Abstract method that implements the handling of messages.
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:param message: the message received
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:returns: the message to send back
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"""
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raise NotImplementedError
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def subscribe(self, *keys):
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"""
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Subscribe this EventHandler to receive events for given keys.
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Note that you can subscribe to the same key several times in which
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case you will need to unsubscribe multiple times in order to stop
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receiving events.
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:param keys: list of keys to subscribe to
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"""
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for key in keys:
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self.server_connector.subscribe(key)
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self.keys.append(key)
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def unsubscribe(self, *keys):
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"""
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Unsubscribe this eventhandler from the given keys.
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:param keys: list of keys to unsubscribe from
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"""
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for key in keys:
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self.server_connector.unsubscribe(key)
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self.keys.remove(key)
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def stop(self):
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self.server_connector.close()
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self.cleanup()
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def cleanup(self):
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"""
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Perform cleanup actions such as releasing database
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connections and stuff like that.
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"""
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@classmethod
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def get_local_instances(cls):
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frame = currentframe()
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if frame is None:
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raise EnvironmentError('inspect.currentframe() is not supported!')
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locals_values = frame.f_back.f_locals.values()
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return {
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instance for instance in locals_values
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if isinstance(instance, cls)
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}
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