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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