import asyncio

from functools import partial

import uuid

from engineio import json

import pickle

from .async_manager import AsyncManager

class AsyncPubSubManager(AsyncManager):

"""Manage a client list attached to a pub/sub backend under asyncio.

This is a base class that enables multiple servers to share the list of

clients, with the servers communicating events through a pub/sub backend.

The use of a pub/sub backend also allows any client connected to the

backend to emit events addressed to Socket.IO clients.

The actual backends must be implemented by subclasses, this class only

provides a pub/sub generic framework for asyncio applications.

:param channel: The channel name on which the server sends and receives

notifications.

"""

name = 'asyncpubsub'

def __init__(self, channel='socketio', write_only=False, logger=None):

super().__init__()

self.channel = channel

self.write_only = write_only

self.host_id = uuid.uuid4().hex

self.logger = logger

def initialize(self):

super().initialize()

if not self.write_only:

self.thread = self.server.start_background_task(self._thread)

self._get_logger().info(self.name + ' backend initialized.')

async def emit(self, event, data, namespace=None, room=None, skip_sid=None,

callback=None, **kwargs):

"""Emit a message to a single client, a room, or all the clients

connected to the namespace.

This method takes care or propagating the message to all the servers

that are connected through the message queue.

The parameters are the same as in :meth:`.Server.emit`.

Note: this method is a coroutine.

"""

if kwargs.get('ignore_queue'):

return await super().emit(

event, data, namespace=namespace, room=room, skip_sid=skip_sid,

callback=callback)

namespace = namespace or '/'

if callback is not None:

if self.server is None:

raise RuntimeError('Callbacks can only be issued from the '

'context of a server.')

if room is None:

raise ValueError('Cannot use callback without a room set.')

id = self._generate_ack_id(room, callback)

callback = (room, namespace, id)

else:

callback = None

message = {'method': 'emit', 'event': event, 'data': data,

'namespace': namespace, 'room': room,

'skip_sid': skip_sid, 'callback': callback,

'host_id': self.host_id}

await self._handle_emit(message) # handle in this host

await self._publish(message) # notify other hosts

async def can_disconnect(self, sid, namespace):

if self.is_connected(sid, namespace):

# client is in this server, so we can disconnect directly

return await super().can_disconnect(sid, namespace)

else:

# client is in another server, so we post request to the queue

await self._publish({'method': 'disconnect', 'sid': sid,

'namespace': namespace or '/',

'host_id': self.host_id})

async def disconnect(self, sid, namespace, **kwargs):

if kwargs.get('ignore_queue'):

return await super().disconnect(

sid, namespace=namespace)

message = {'method': 'disconnect', 'sid': sid,

'namespace': namespace or '/', 'host_id': self.host_id}

await self._handle_disconnect(message) # handle in this host

await self._publish(message) # notify other hosts

async def enter_room(self, sid, namespace, room, eio_sid=None):

if self.is_connected(sid, namespace):

# client is in this server, so we can disconnect directly

return await super().enter_room(sid, namespace, room,

eio_sid=eio_sid)

else:

message = {'method': 'enter_room', 'sid': sid, 'room': room,

'namespace': namespace or '/', 'host_id': self.host_id}

await self._publish(message) # notify other hosts

async def leave_room(self, sid, namespace, room):

if self.is_connected(sid, namespace):

# client is in this server, so we can disconnect directly

return await super().leave_room(sid, namespace, room)

else:

message = {'method': 'leave_room', 'sid': sid, 'room': room,

'namespace': namespace or '/', 'host_id': self.host_id}

await self._publish(message) # notify other hosts

async def close_room(self, room, namespace=None):

message = {'method': 'close_room', 'room': room,

'namespace': namespace or '/', 'host_id': self.host_id}

await self._handle_close_room(message) # handle in this host

await self._publish(message) # notify other hosts

async def _publish(self, data):

"""Publish a message on the Socket.IO channel.

This method needs to be implemented by the different subclasses that

support pub/sub backends.

"""

raise NotImplementedError('This method must be implemented in a '

'subclass.') # pragma: no cover

async def _listen(self):

"""Return the next message published on the Socket.IO channel,

blocking until a message is available.

This method needs to be implemented by the different subclasses that

support pub/sub backends.

"""

raise NotImplementedError('This method must be implemented in a '

'subclass.') # pragma: no cover

async def _handle_emit(self, message):

# Events with callbacks are very tricky to handle across hosts

# Here in the receiving end we set up a local callback that preserves

# the callback host and id from the sender

remote_callback = message.get('callback')

remote_host_id = message.get('host_id')

if remote_callback is not None and len(remote_callback) == 3:

callback = partial(self._return_callback, remote_host_id,

*remote_callback)

else:

callback = None

await super().emit(message['event'], message['data'],

namespace=message.get('namespace'),

room=message.get('room'),

skip_sid=message.get('skip_sid'),

callback=callback)

async def _handle_callback(self, message):

if self.host_id == message.get('host_id'):

try:

sid = message['sid']

id = message['id']

args = message['args']

except KeyError:

return

await self.trigger_callback(sid, id, args)

async def _return_callback(self, host_id, sid, namespace, callback_id,

*args):

# When an event callback is received, the callback is returned back

# the sender, which is identified by the host_id

if host_id == self.host_id:

await self.trigger_callback(sid, callback_id, args)

else:

await self._publish({'method': 'callback', 'host_id': host_id,

'sid': sid, 'namespace': namespace,

'id': callback_id, 'args': args})

async def _handle_disconnect(self, message):

await self.server.disconnect(sid=message.get('sid'),

namespace=message.get('namespace'),

ignore_queue=True)

async def _handle_enter_room(self, message):

sid = message.get('sid')

namespace = message.get('namespace')

if self.is_connected(sid, namespace):

await super().enter_room(sid, namespace, message.get('room'))

async def _handle_leave_room(self, message):

sid = message.get('sid')

namespace = message.get('namespace')

if self.is_connected(sid, namespace):

await super().leave_room(sid, namespace, message.get('room'))

async def _handle_close_room(self, message):

await super().close_room(room=message.get('room'),

namespace=message.get('namespace'))

async def _thread(self):

while True:

try:

async for message in self._listen(): # pragma: no branch

data = None

if isinstance(message, dict):

data = message

else:

if isinstance(message, bytes): # pragma: no cover

try:

data = pickle.loads(message)

except:

pass

if data is None:

try:

data = json.loads(message)

except:

pass

if data and 'method' in data:

self._get_logger().debug('pubsub message: {}'.format(

data['method']))

try:

if data['method'] == 'callback':

await self._handle_callback(data)

elif data.get('host_id') != self.host_id:

if data['method'] == 'emit':

await self._handle_emit(data)

elif data['method'] == 'disconnect':

await self._handle_disconnect(data)

elif data['method'] == 'enter_room':

await self._handle_enter_room(data)

elif data['method'] == 'leave_room':

await self._handle_leave_room(data)

elif data['method'] == 'close_room':

await self._handle_close_room(data)

except asyncio.CancelledError:

raise # let the outer try/except handle it

except:

self.server.logger.exception(

'Unknown error in pubsub listening task')

except asyncio.CancelledError: # pragma: no cover

break

except: # pragma: no cover

import traceback

traceback.print_exc()