I am only using one channel name and my expectation is that only one
instance of the background worker class should be initiated/used. Instead,
I am seeing a new class being initiated for each call routed to the
background worker class. This is unexpected...
On Thursday, June 21, 2018 at 3:55:23 PM UTC-4, Andrew Godwin wrote:
>
> The worker server tries to keep one application instance open per incoming
> channel name, but that's no guarantee. It will always make a new instance
> for different channel names. What kind of behaviour are you expecting?
>
> Andrew
>
> On Tue, Jun 19, 2018 at 6:45 AM itsnate_b <nathan...@gmail.com
> <javascript:>> wrote:
>
>> I am using Django 2.0.5, Python 3.6.2, Django Channels 2.1.1, aiohttp
>> 3.1.3.
>>
>> I have created a background worker class which is initialized on a route
>> to the appropriate event/function. Problem is that it initializes a *new*
>> instance of the class on every triggered call, meaning that I cannot access
>> contextual variables (they don't persist). Is there a way to trigger the
>> same (i.e. first) and only class repeatedly on each routed call? I can
>> change it all to function calls with global variables stored for the
>> relevant asyncio futures and/or booleans, but would really prefer not to do
>> that....any suggestions?
>>
>> My (simplified) code:
>>
>> *consumers.py*
>>
>> from channels.generic.websocket import AsyncWebsocketConsumer
>> from channels.consumer import AsyncConsumer
>> from channels.layers import get_channel_layer
>> import json
>> import asyncio
>> import aiohttp
>> import datetime
>>
>>
>> class mainConsumer(AsyncWebsocketConsumer):
>>
>> async def connect(self):
>> await self.channel_layer.group_add('myGroup', self.channel_name)
>> await self.accept()
>>
>> async def disconnect(self, closeCode):
>> await self.channel_layer.group_discard('myGroup',
>> self.channel_name)
>>
>> async def receive(self, text_data):
>> eventData = json.loads(text_data)
>> print(eventData)
>> if eventData['toggle'] == 'on':
>> await self.channel_layer.send('myToggle',{"type":
>> "openConnection"})
>> elif eventData['toggle'] == 'off':
>> await self.channel_layer.send('myToggle',{"type":
>> "closeConnection"})
>>
>> async def myUpdate(self, data):
>> updateMsg = #some data processing here
>> await self.send(text_data=json.dumps(updateMsg))
>>
>>
>> class backgroundConsumer(AsyncConsumer):
>>
>> def __init__(self, scope):
>> self.scope = scope
>> self.turnOnListener = True
>> self.channelLayer = get_channel_layer()
>> self.t1 = None
>> print('inside init') # this will print init on every
>> channel_layer.send to 'myToggle' in mainConsumer
>>
>> async def listen(self):
>>
>> async with aiohttp.ClientSession() as session:
>> async with session.ws_connect('...streaming url...',
>> ssl=False) as ws:
>> await ws.send_str('...some string...')
>> async for msg in ws:
>> if msg.type == aiohttp.WSMsgType.TEXT:
>> if msg.data.startswith('2'):
>> await ws.send_str('3')
>> else:
>> await self.parseListenData(msg)
>>
>> async def parseListenData(self, msgContent):
>> # process and create updateMsg dict with type: 'myUpdate' (so
>> that it gets to the myUpdate function in main Consumer)
>> await self.channelLayer.group_send('myGroup', updateMsg)
>>
>> async def openConnection(self, event):
>> if(self.turnOnListener): *# THIS IS ALWAYS TRUE BECAUSE THE
>> ROUTE INITIALIZES A NEW INSTANCE OF THIS CLASS!!*
>> await self.channelLayer.group_add(
>> 'myGroup',
>> self.channel_name,
>> )
>> self.turnOnListener = False # This only changes it for the
>> current instance (obviously)
>> loop = asyncio.get_event_loop()
>> self.t1 = asyncio.run_coroutine_threadsafe(self.listen(),
>> loop=loop)
>> else:
>> print('already turned on listener')
>>
>> async def closeConnection(self, event):
>> loop = asyncio.get_event_loop()
>> loop.call_soon_threadsafe(self.t1.cancel) *# t1 is always None
>> because the route initialized a new instance of this class!!*
>>
>> *routing.py*
>> from channels.auth import AuthMiddlewareStack
>> from channels.routing import ProtocolTypeRouter, URLRouter,
>> ChannelNameRouter
>> import dashboard.routing
>> from dashboard.consumers import backgroundConsumer
>>
>> application = ProtocolTypeRouter({
>> # (http->django views is added by default)
>> 'websocket': AuthMiddlewareStack(
>> URLRouter(
>> dashboard.routing.websocket_urlpatterns
>> )
>> ),
>> 'channel': ChannelNameRouter({
>> "myToggle": backgroundConsumer,
>> }),
>> })
>>
>>
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