I'm using a websocket to feed a chart with live data. As soon as the websocket is opened, I want to send the client historical data, so that the chart doesn't start loading only with the current values.
I want to do something like this, if it was possible:
from channels.db import database_sync_to_async
class StreamConsumer(AsyncConsumer):
async def websocket_connect(self, event):
# When the connection is first opened, also send the historical data
data = get_historical_data(1)
await self.send({
'type': 'websocket.accept',
'text': data # This doesn't seem possible
})
# This is what I use to send the messages with the live data
async def stream(self, event):
data = event["data"]
await self.send({
'type': 'websocket.send',
'text': data
})
#database_sync_to_async
def get_historical_data(length):
.... fetch data from the DB
What's the right way to do it?
First you need to accept the connection before sending data to the client. I assume you're using AsyncWebsocketConsumer(and you should) as the more low-level AsyncConsumer has not method websocket_connect
from channels.db import database_sync_to_async
class StreamConsumer(AsyncWebsocketConsumer):
async def websocket_connect(self, event):
# When the connection is first opened, also send the historical data
data = get_historical_data(1)
await self.accept()
await self.send(data)
# This is what I use to send the messages with the live data
async def stream(self, event):
data = event["data"]
await self.send(data)
Related
I want to connect my Django WebSocket with a third-party web socket. This program is one I wrote, and it functions properly. To avoid having to re-login with the third-party API, I have now added the code to check whether the same room is present in my database. if we use the same API KEY to re-connect to the third-party API. It gives the following error:
{"event":"login","status":401,"message":"Connected from another location"}
I want to see if the same cryptocurrency coin is already connected or not. We don't want to logon with the same API KEY once we're connected. I have two issues here:
Don't send the login request to that web socket again.
Don't send the subscribe request, if the same coin already exists. Let's say BTCUSD already connected and giving me the data. I want to just connect to the next user to same room and get the data on next request.
import websocket
import time
import ssl
from channels.generic.websocket import AsyncWebsocketConsumer
from .models import Room
login = {
"event": "login",
"data": {
"apiKey": "API_KEY",
},
}
class CryptoConsumer(AsyncWebsocketConsumer):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.ws = websocket.WebSocket(sslopt={"cert_reqs": ssl.CERT_NONE})
self.ws.connect("wss://crypto.financialmodelingprep.com")
async def connect(self):
self.room_name = self.scope["url_route"]["kwargs"]["room_name"]
self.room_group_name = "crypto_%s" % self.room_name
# ****** Code Block ******
subscribe = {
"event": "subscribe",
"data": {
"ticker": self.room_name,
},
}
room = await Room.add(self.room_name) # Method in models.py to add the user and return True
if room is False:
self.ws.send(json.dumps(login))
print("The group with the name %s doesn't exist" % self.room_group_name)
time.sleep(1)
self.ws.send(json.dumps(subscribe))
# ****** End Code Block ******
# Join room group
await self.channel_layer.group_add(self.room_group_name, self.channel_name)
await self.accept()
async def disconnect(self, close_code):
unsubscribe = {
"event": "unsubscribe",
"data": {
"ticker": self.room_name,
},
}
self.ws.send(json.dumps(unsubscribe))
self.ws.close()
# Leave room group
await self.channel_layer.group_discard(self.room_group_name, self.channel_name)
# Receive message from WebSocket
async def receive(self, text_data="{'text': 'Dummy Text'}"):
text_data_json = json.loads(text_data)
message = text_data_json["message"]
message = str(self.ws.recv())
# Send message to room group
await self.channel_layer.group_send(
self.room_group_name, {"type": "chat_message", "message": message}
)
# Receive message from room group
async def chat_message(self, event):
message = event["message"]
# Send message to WebSocket
await self.send(text_data=json.dumps({"message": message}))
Note: Why I want to do this entire step because we don't want the API KEY made public.
So, the code coming from the front end will connect to our Django web socket, and then we'll connect to the third-party web socket and return the data that was sent by them.
The SQL update does not seem to be being enacted upon, and no errors are being thrown either. Below is a simplified version of my code. For context, the "choice" field in the model is a Boolean Field with a default of False, and a user may (ideally) change this by sending a JSON package with the "CHOICE" event and "Yes" message.
consumers.py
import json
from channels.generic.websocket import AsyncJsonWebsocketConsumer
from asgiref.sync import sync_to_async
from .models import Room
class Consumer(AsyncJsonWebsocketConsumer):
async def connect(self):
self.room_code = self.scope['url_route']['kwargs']['room_code']
#Websockets connection code
async def disconnect(self):
#Websockets disconnect code
async def receive(self, text_data):
response = json.loads(text_data)
event = response.get("event", None)
message = response.get("message", None)
if event == "CHOICE":
room_set = await sync_to_async(Room.objects.filter)(room_code=self.room_code)
room = await sync_to_async(room_set.first)()
if (not room.choice) and message["choice"] == 'Yes':
sync_to_async(room_set.update)(choice=True) #line seems to not be working
elif room.choice and message["choice"] == 'No':
sync_to_async(room_set.update)(choice=False)
#code to send message to group over Websockets
#code regarding other events
async def send_message(self, res):
#Websockets send message code
I've tried to only include the relevant code here, but if more is needed please let me know. Thanks in advance!
I fixed this issue by adding await before the sync_to_async(room.update)(choice=True) lines. It seems without an await it will move onto the next line of code before completing the SQL update, causing the update to not go through.
I am using AsyncWebsocketConsumer in channels to create basic group messaging
saving in a database or any other process who's data should not be sent to WebSocket works fine, but when I try to fetch all previous messages at socket open function, it is not sending data to socket but data is retrieved...
basically, it is running both processes parallelly, so do I need to use syncWebsocketConsumer and use async and await were required ? or is there anything to make few things synchronized in async consumers ?
class ChatConsumer(AsyncWebsocketConsumer):
...
async def receive(self, text_data):
text_data_json = json.loads(text_data)
message = text_data_json['message']
user = text_data_json['user']
print(text_data_json['type'])
#using init_messages for fetching
await self.channel_layer.group_send(
self.room_group_name,{
'type': text_data_json['type'],
'message':message,
'user': text_data_json['user']
}
)
print("sended")
async def init_messages(self,event):
messages = await sync_to_async(get_last_10_messages)(self.room_name)
print(messages)
messages = self.parse_messages(messages)
self.send(text_data=json.dumps({
'messages':messages,
}))
parse_messages simply gives dictionary
In room.html
chatSocket.onopen = function(e){
chatSocket.send(JSON.stringify({
'type': "init_messages",
'message':"",
'user': user_username,
}));
console.log('for debug')
}
I am using a combination of DRF 3.11.0 and Channels 2.4.0 to implement a backend, and it is hosted on Heroku on 1 dyno with a Redis resource attached. I have a socket on my React frontend that successfully sends/received from the backend server.
I am having an issues where any message sent back to the front end over the socket is being sent twice. I have confirmed through console.log that the front end is only pinging the back end once. I can confirm through print() inside of the API call that the function is only calling async_to_sync(channel_layer.group_send) once as well. The issue is coming from my consumer - when I use print(self.channel_name) inside of share_document_via_videocall(), I can see that two instances with different self.channel_names are being called (specific.AOQenhTn!fUybdYEsViaP and specific.AOQenhTn!NgtWxuiHtHBw. It seems like the consumer has connected to two separate channels, but I'm not sure why. When I put print() statements in my connect() I only see it go through the connect process once.
How do I ensure that I am only connected to one channel?
in settings.py:
CHANNEL_LAYERS = {
'default': {
'BACKEND': 'channels_redis.core.RedisChannelLayer',
'CONFIG': {
#"hosts": [('127.0.0.1', 6379)],
"hosts": [(REDIS_HOST)],
},
},
}
Consumer:
import json
from asgiref.sync import async_to_sync
from channels.db import database_sync_to_async
from channels.generic.websocket import AsyncWebsocketConsumer
from rest_framework.authtoken.models import Token
from django.contrib.auth.models import AnonymousUser
from .exceptions import ClientError
import datetime
from django.utils import timezone
class HeaderConsumer(AsyncWebsocketConsumer):
async def connect(self):
print("connecting")
await self.accept()
print("starting")
print(self.channel_name)
await self.send("request_for_token")
async def continue_connect(self):
print("continuing")
print(self.channel_name)
await self.get_user_from_token(self.scope['token'])
await self.channel_layer.group_add(
"u_%d" % self.user['id'],
self.channel_name,
)
#... more stuff
async def disconnect(self, code):
await self.channel_layer.group_discard(
"u_%d" % self.user['id'],
self.channel_name,
)
async def receive(self, text_data):
text_data_json = json.loads(text_data)
if 'token' in text_data_json:
self.scope['token'] = text_data_json['token']
await self.continue_connect()
async def share_document_via_videocall(self, event):
# Send a message down to the client
print("share_document received")
print(event)
print(self.channel_name)
print(self.user['id'])
await self.send(text_data=json.dumps(
{
"type": event['type'],
"message": event["message"],
},
))
#database_sync_to_async
def get_user_from_token(self, t):
try:
print("trying token" + t)
token = Token.objects.get(key=t)
self.user = token.user.get_profile.json()
except Token.DoesNotExist:
print("failed")
self.user = AnonymousUser()
REST API call:
class ShareViaVideoChat(APIView):
permission_classes = (permissions.IsAuthenticated,)
def post(self, request, format=None):
data = request.data
recipient_list = data['recipient_list']
channel_layer = get_channel_layer()
for u in recipient_list:
if u['id'] != None:
print("sending to:")
print('u_%d' % u['id'])
async_to_sync(channel_layer.group_send)(
'u_%d' % u['id'],
{'type': 'share_document_via_videocall',
'message': {
'document': {'data': {}},
'sender': {'name': 'some name'}
}
}
)
return Response()
with respect to you getting to calls with different channel names are you sure your frontend has not connected twice to the consumer? Check in the debug console in your browser.
i get same problem with nextjs as a frontend of Django channels WebSocket server.
and after searching i found the problem related with tow things:
1- react strict mode (the request sending twice) :
to disable react strict mode in next.js , go to module name "next.config.js" , and change the value for strict mode to false , as the following :
/** #type {import('next').NextConfig} */
const nextConfig = {
reactStrictMode: false,
}
module.exports = nextConfig
2- in nextjs the code run twice (outside useEffect Hook) , one on server side and the second on the client side (which means each user will connect to websocket server twice, and got two channels name , and join to same group twice each time with different channel name . ) ,
so i changed my codes to connect with Django channels server only from client side , if you like see my full code / example , kindly visit the following URL , and note the checking code about "typeof window === "undefined":
frontend nextjs code :
https://stackoverflow.com/a/72288219/12662056
i don't know if my problem same your problem , but i hope that helpful.
Django Channels docs has following basic example of a Server Sent Events. AsyncHttpConsumer
from datetime import datetime
from channels.generic.http import AsyncHttpConsumer
class ServerSentEventsConsumer(AsyncHttpConsumer):
async def handle(self, body):
await self.send_headers(headers=[
(b"Cache-Control", b"no-cache"),
(b"Content-Type", b"text/event-stream"),
(b"Transfer-Encoding", b"chunked"),
])
while True:
payload = "data: %s\n\n" % datetime.now().isoformat()
await self.send_body(payload.encode("utf-8"), more_body=True)
await asyncio.sleep(1)
I want to accept messages sent via channel_layer and send them as events.
I changed the handle method, so it subscribes the new channel to a group. And I'm planning to send messages to the channel layer via channel_layer.group_send
But I couldn't figure out how to get the messages sent to the group, within handle method. I tried awaiting for the channel_layer.receive, it doesn't seem to work.
class ServerSentEventsConsumer(AsyncHttpConsumer):
group_name = 'my_message_group'
async def myevent(self, event):
# according to the docs, this method will be called \
# when a group received a message with type 'myevent'
# I'm not sure how to get this event within `handle` method's while loop.
pass
async def handle(self, body):
await self.channel_layer.group_add(
self.group_name,
self.channel_name
)
await self.send_headers(headers=[
(b"Cache-Control", b"no-cache"),
(b"Content-Type", b"text/event-stream"),
(b"Transfer-Encoding", b"chunked"),
])
while True:
payload = "data: %s\n\n" % datetime.now().isoformat()
result = await self.channel_receive()
payload = "data: %s\n\n" % 'received'
I'm sending the messages to channel_layer like below: ( from a management command)
def send_event(event_data):
group_name = 'my_message_group'
channel_layer = get_channel_layer()
async_to_sync(channel_layer.group_send)(
group_name,
{
'type': 'myevent',
'data': [event_data]
}
)
I had the same issue and I even went to dig into Django Channels code but without success.
... Until I found this answer in this (still opened) issue: https://github.com/django/channels/issues/1302#issuecomment-508896846
That should solve your issue.
In your case the code would be (or something quite similar):
class ServerSentEventsConsumer(AsyncHttpConsumer):
group_name = 'my_message_group'
async def http_request(self, message):
if "body" in message:
self.body.append(message["body"])
if not message.get("more_body"):
await self.handle(b"".join(self.body))
async def myevent(self, event):
# according to the docs, this method will be called \
# when a group received a message with type 'myevent'
# I'm not sure how to get this event within `handle` method's while loop.
pass
async def handle(self, body):
await self.channel_layer.group_add(
self.group_name,
self.channel_name
)
await self.send_headers(headers=[
(b"Cache-Control", b"no-cache"),
(b"Content-Type", b"text/event-stream"),
(b"Transfer-Encoding", b"chunked"),
])