182 lines
7.4 KiB
Python
182 lines
7.4 KiB
Python
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from functools import partial
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import uuid
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from engineio import json
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import pickle
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from .base_manager import BaseManager
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class PubSubManager(BaseManager):
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"""Manage a client list attached to a pub/sub backend.
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This is a base class that enables multiple servers to share the list of
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clients, with the servers communicating events through a pub/sub backend.
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The use of a pub/sub backend also allows any client connected to the
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backend to emit events addressed to Socket.IO clients.
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The actual backends must be implemented by subclasses, this class only
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provides a pub/sub generic framework.
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:param channel: The channel name on which the server sends and receives
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notifications.
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"""
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name = 'pubsub'
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def __init__(self, channel='socketio', write_only=False, logger=None):
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super(PubSubManager, self).__init__()
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self.channel = channel
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self.write_only = write_only
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self.host_id = uuid.uuid4().hex
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self.logger = logger
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def initialize(self):
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super(PubSubManager, self).initialize()
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if not self.write_only:
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self.thread = self.server.start_background_task(self._thread)
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self._get_logger().info(self.name + ' backend initialized.')
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def emit(self, event, data, namespace=None, room=None, skip_sid=None,
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callback=None, **kwargs):
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"""Emit a message to a single client, a room, or all the clients
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connected to the namespace.
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This method takes care or propagating the message to all the servers
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that are connected through the message queue.
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The parameters are the same as in :meth:`.Server.emit`.
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"""
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if kwargs.get('ignore_queue'):
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return super(PubSubManager, self).emit(
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event, data, namespace=namespace, room=room, skip_sid=skip_sid,
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callback=callback)
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namespace = namespace or '/'
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if callback is not None:
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if self.server is None:
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raise RuntimeError('Callbacks can only be issued from the '
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'context of a server.')
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if room is None:
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raise ValueError('Cannot use callback without a room set.')
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id = self._generate_ack_id(room, callback)
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callback = (room, namespace, id)
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else:
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callback = None
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self._publish({'method': 'emit', 'event': event, 'data': data,
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'namespace': namespace, 'room': room,
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'skip_sid': skip_sid, 'callback': callback,
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'host_id': self.host_id})
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def can_disconnect(self, sid, namespace):
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if self.is_connected(sid, namespace):
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# client is in this server, so we can disconnect directly
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return super().can_disconnect(sid, namespace)
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else:
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# client is in another server, so we post request to the queue
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self._publish({'method': 'disconnect', 'sid': sid,
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'namespace': namespace or '/'})
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def disconnect(self, sid, namespace=None, **kwargs):
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if kwargs.get('ignore_queue'):
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return super(PubSubManager, self).disconnect(
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sid, namespace=namespace)
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self._publish({'method': 'disconnect', 'sid': sid,
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'namespace': namespace or '/'})
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def close_room(self, room, namespace=None):
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self._publish({'method': 'close_room', 'room': room,
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'namespace': namespace or '/'})
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def _publish(self, data):
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"""Publish a message on the Socket.IO channel.
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This method needs to be implemented by the different subclasses that
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support pub/sub backends.
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"""
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raise NotImplementedError('This method must be implemented in a '
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'subclass.') # pragma: no cover
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def _listen(self):
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"""Return the next message published on the Socket.IO channel,
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blocking until a message is available.
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This method needs to be implemented by the different subclasses that
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support pub/sub backends.
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"""
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raise NotImplementedError('This method must be implemented in a '
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'subclass.') # pragma: no cover
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def _handle_emit(self, message):
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# Events with callbacks are very tricky to handle across hosts
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# Here in the receiving end we set up a local callback that preserves
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# the callback host and id from the sender
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remote_callback = message.get('callback')
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remote_host_id = message.get('host_id')
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if remote_callback is not None and len(remote_callback) == 3:
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callback = partial(self._return_callback, remote_host_id,
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*remote_callback)
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else:
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callback = None
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super(PubSubManager, self).emit(message['event'], message['data'],
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namespace=message.get('namespace'),
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room=message.get('room'),
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skip_sid=message.get('skip_sid'),
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callback=callback)
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def _handle_callback(self, message):
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if self.host_id == message.get('host_id'):
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try:
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sid = message['sid']
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id = message['id']
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args = message['args']
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except KeyError:
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return
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self.trigger_callback(sid, id, args)
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def _return_callback(self, host_id, sid, namespace, callback_id, *args):
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# When an event callback is received, the callback is returned back
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# to the sender, which is identified by the host_id
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self._publish({'method': 'callback', 'host_id': host_id,
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'sid': sid, 'namespace': namespace, 'id': callback_id,
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'args': args})
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def _handle_disconnect(self, message):
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self.server.disconnect(sid=message.get('sid'),
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namespace=message.get('namespace'),
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ignore_queue=True)
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def _handle_close_room(self, message):
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super(PubSubManager, self).close_room(
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room=message.get('room'), namespace=message.get('namespace'))
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def _thread(self):
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for message in self._listen():
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data = None
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if isinstance(message, dict):
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data = message
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else:
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if isinstance(message, bytes): # pragma: no cover
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try:
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data = pickle.loads(message)
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except:
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pass
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if data is None:
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try:
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data = json.loads(message)
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except:
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pass
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if data and 'method' in data:
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self._get_logger().info('pubsub message: {}'.format(
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data['method']))
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try:
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if data['method'] == 'emit':
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self._handle_emit(data)
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elif data['method'] == 'callback':
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self._handle_callback(data)
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elif data['method'] == 'disconnect':
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self._handle_disconnect(data)
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elif data['method'] == 'close_room':
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self._handle_close_room(data)
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except:
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self.server.logger.exception(
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'Unknown error in pubsub listening thread')
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