Possible reasons for Django Channels intermittently functioning - django

Question

I am attempting to use Django Channels on my digital ocean ubuntu 18 droplet to serve a 'video' feed from a webcam attached to a raspberry pi. The raspberry pi is using python websockets-client and openCV to send jpeg images quickly (every 0.05 seconds).
The issue is that this will work great, streaming for 10+ minutes perfectly with good frame rate, and I will think I have got it working. Then the next day, it will stream for about 10 seconds before the frame rate on the browser becomes very laggy and then stops receiving images. The Raspberry pi then disconnects from the websocket from what appears to be my server disconnecting it, I cannot get it to stream longer than a few seconds. Why would it work perfectly one day, and not the next? Nothing obvious has changed.
The reason I think it is my server/channels/redis causing the problem:
Before the raspberry pi even seems to be having any trouble, the video feed being shown on the browser will become very laggy then will stop getting new images entirely. Then a few seconds later my raspberry pi socket will disconnect from the websocket.
What I have Tried:
I have done a speed test on my internet connection and it is 50mb down/15mb up.
I have tried reducing the frame rate to something very slow, like one image per second, and it will still stop working.
I have checked on my memory and CPU of both my droplet and raspberry pi. When a crash occurs, CPU on both machines are typically below 25% usage, and memory is typically below 40% usage.
I changed some of the redis settings in settings.py shown below, did not seem to have any effect.
What would cause an intermittently functioning websocket? I have changed my redis settings in settings.py, but I am not sure what else to change or attempt to debug.
I followed the tutorial on deployment here: Channels Docs
Channels code:
Consumers.py
from channels.generic.websocket import AsyncWebsocketConsumer
#import urllib.parse as urlparse
#from urllib.parse import parse_qs
from channels.db import database_sync_to_async
from accounts.models import CustomUser
from rest_framework.authtoken.models import Token
#websocket for video connection
class StreamConsumer(AsyncWebsocketConsumer):
async def connect(self):
self.room_name = self.scope['url_route']['kwargs']['device_id']
print(self.room_name)
self.room_group_name = 'stream_%s' % self.room_name
self.token_passed = self.scope['query_string'].decode() #token passed in with ws://url/?token
self.token_actual = await self.get_token(self.room_name) #go get actual token for this monitor
# Join room group
await self.channel_layer.group_add(
self.room_group_name,
self.channel_name
)
#check to ensure tokens match, if they do, allow connection
if self.token_passed == self.token_actual:
await self.accept()
print('True')
else:
print(self.token_passed)
print(self.token_actual)
await self.close()
async def disconnect(self, close_code):
# Leave room group
print(close_code)
print("closing")
await self.channel_layer.group_discard(
self.room_group_name,
self.channel_name
)
#database_sync_to_async
def get_token(self, monitor_serial):
try:
monitor = CustomUser.objects.get(deviceSerial=monitor_serial)
token = Token.objects.get(user=monitor)
return token.key
except:
return "user not available"
# Receive message from WebSocket
async def receive(self, bytes_data=None, text_data=None):
# Send message to room group
await self.channel_layer.group_send(
self.room_group_name,
{
'type': 'stream_data',
'bytes_data': bytes_data,
'text_data': text_data
}
)
# Receive message from room group
async def stream_data(self, event):
bytes_data = event['bytes_data']
text_data = event['text_data']
# Send message to WebSocket
await self.send(bytes_data=bytes_data, text_data=text_data)
class StatusConsumer(AsyncWebsocketConsumer):
async def connect(self):
self.room_name = self.scope['url_route']['kwargs']['device_id']
self.room_group_name = 'status_%s' % self.room_name
self.token_passed = self.scope['query_string'].decode() #token passed in with ws://url/?token
self.token_actual = await self.get_token(self.room_name) #go get actual token for this monitor
# Join room group
await self.channel_layer.group_add(
self.room_group_name,
self.channel_name
)
#check to ensure tokens match, if they do, allow connection
if self.token_passed == self.token_actual:
await self.accept()
else:
print(self.token_passed)
print(self.token_actual)
await self.close()
async def disconnect(self, close_code):
# Leave room group
print(close_code)
print("closing")
await self.channel_layer.group_discard(
self.room_group_name,
self.channel_name
)
#database_sync_to_async
def get_token(self, monitor_serial):
monitor = CustomUser.objects.get(deviceSerial=monitor_serial)
token = Token.objects.get(user=monitor)
return token.key
# Receive message from WebSocket
async def receive(self, text_data=None):
# Send message to room group
await self.channel_layer.group_send(
self.room_group_name,
{
'type': 'status_data',
'text_data': text_data
}
)
# Receive message from room group
async def status_data(self, event):
#bytes_data = event['bytes_data']
text_data = event['text_data']
# Send message to WebSocket
#await self.send(bytes_data=bytes_data, text_data=text_data)
await self.send(text_data=text_data)
asgi.py
import os
from django.conf.urls import url
from django.core.asgi import get_asgi_application
# Fetch Django ASGI application early to ensure AppRegistry is populated
# before importing consumers and AuthMiddlewareStack that may import ORM
# models.
try:
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "polysensesite.settings")
except:
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mysite.settings")
django_asgi_app = get_asgi_application()
from channels.auth import AuthMiddlewareStack
from channels.routing import ProtocolTypeRouter, URLRouter
from .consumers import StreamConsumer, StatusConsumer
application = ProtocolTypeRouter({
# Django's ASGI application to handle traditional HTTP requests
"http": django_asgi_app,
# WebSocket chat handler
"websocket": AuthMiddlewareStack(
URLRouter([
url(r"^stream/(?P<device_id>[\d\-]+)/$", StreamConsumer.as_asgi()),
url(r"^status/(?P<device_id>[\d\-]+)/$", StatusConsumer.as_asgi()),
])
),
})
settings.py
CHANNEL_LAYERS = {
"default": {
"BACKEND": "channels_redis.core.RedisChannelLayer",
"CONFIG": {
"hosts": [("localhost", 6379)],
"capacity": 5000,
"expiry": 5,
},
},
}
I put some print statements on the browser, consumers, and raspberry pi, and it seems like everything is working except the raspberry pi stops receiving messages (but is still attempting to send images) then the socket closes abruptly and I get this message from Daphne:
127.0.0.1:37154 - - [30/May/2021:16:56:32] "WSDISCONNECT /stream/XXXXXXX/" - -
1001
closing
2021-05-30 16:56:33,364 ERROR Exception inside application:
Traceback (most recent call last):
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/routing.py", line 71, in __call__
return await application(scope, receive, send)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/sessions.py", line 47, in __call__
return await self.inner(dict(scope, cookies=cookies), receive, send)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/sessions.py", line 254, in __call__
return await self.inner(wrapper.scope, receive, wrapper.send)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/auth.py", line 181, in __call__
return await super().__call__(scope, receive, send)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/middleware.py", line 26, in __call__
return await self.inner(scope, receive, send)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/routing.py", line 160, in __call__
send,
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/consumer.py", line 94, in app
return await consumer(scope, receive, send)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/consumer.py", line 59, in __call__
[receive, self.channel_receive], self.dispatch
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/utils.py", line 51, in await_many_dispatch
await dispatch(result)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/consumer.py", line 73, in dispatch
await handler(message)
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels/generic/websocket.py", line 198, in websocket_receive
await self.receive(bytes_data=message["bytes"])
File "./polysensesite/consumers.py", line 69, in receive
'text_data': text_data
File "/home/polysense/polysensesite/psvirtualenv/lib/python3.6/site-packages/channels_redis/core.py", line 667, in group_send
key, min=0, max=int(time.time()) - int(self.expiry)
aioredis.errors.ConnectionForcedCloseError