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')
}
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.
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)
I am using Django Channels and RabbitMQ pika, for the first time. I am trying to consume from RabbitMQ queue. I am using Django Channels AsyncConsumer to group send it to everyone connected in the websocket.
User type 1 : Can create a task
User type 2 : Can accept the task.
Use case : When user type 1 creates the task it is published in the rabbitmq. When it is consumed from the queue, it has to be group-sent to frontend. And when the user type 2 accepts the task other instances of user type 2 cannot accept the same and we consume from the queue again and send the next task in the queue to everyone.
I have created the connection in a different thread using sync_to_async I am appending it to an in-memory list from the callback function.
And whenever someone accepts I just pop it out of the list and acknowledge the queue.
class AcceptTaskConsumer(AsyncConsumer):
body = [] #IN MEMORY LIST
delivery = {} #To store ack delivery_tag
async def websocket_connect(self, event):
print("AcceptTaskConsumer connected", event)
AcceptTaskConsumer.get_task() #STARTS Queue listener in new thread
self.room_group_name = "user_type_2"
await self.channel_layer.group_add(
self.room_group_name,
self.channel_name
)
await self.send({
"type": "websocket.accept"
})
async def websocket_receive(self, event):
if event["text"] == "Hi": #If connecting first time
if AcceptTaskConsumer.body:
await self.channel_layer.group_send(
self.room_group_name,
{
"type": "message",
"text": AcceptTaskConsumer.body[0]["body"]
}
)
else:
await self.channel_layer.group_send(
self.room_group_name,
{
"type": "message",
"text": "No New Tasks"
}
)
else: #When someone accepts a task-> ack and send next task in queue
print(json.loads(event["text"])["id"])
AcceptTaskConsumer.channel.basic_ack(delivery_tag=AcceptTaskConsumer.delivery[json.loads(event["text"])["id"]])
AcceptTaskConsumer.delivery.pop(json.loads(event["text"])["id"])
AcceptTaskConsumer.body.pop(0)
await self.channel_layer.group_send(
self.room_group_name,
{
"type": "message",
"text": "No New Tasks"
}
)
if AcceptTaskConsumer.body:
await self.channel_layer.group_send(
self.room_group_name,
{
"type": "message",
"text": AcceptTaskConsumer.body[0]["body"]
}
)
async def message(self, event):
await self.send({
"type": "websocket.send",
"text": event["text"]
})
#classmethod
#sync_to_async
def get_task(cls): #pika consumer
cls.connection = pika.BlockingConnection(
pika.ConnectionParameters(host='localhost'))
cls.channel = cls.connection.channel()
cls.channel.queue_declare(queue='task_', arguments={"x-max-priority": 3})
cls.channel.basic_consume(
queue='task_', on_message_callback=AcceptTaskConsumer.callback, auto_ack=False)
cls.channel.start_consuming()
#classmethod
def callback(cls, ch, method, properties, body):
task_obj = {"body": json.dumps(body.decode("utf-8")),
"delivery_tag": method.delivery_tag}
AcceptTaskConsumer.body.append(task_obj)
AcceptTaskConsumer.delivery[json.loads(json.loads(task_obj["body"]))["id"]] = method.delivery_tag
cls.channel.stop_consuming()
async def websocket_disconnect(self, event):
print(event)
await self.send({
"type": "websocket.close"
})
await self.channel_layer.group_discard(
self.room_group_name,
self.channel_name
)
I am pretty sure this is not the right way to do it, because it's not working as expected
I run into frequent errors like.
39 of 169 channels over capacity in group delivery
pika.exceptions.StreamLostError: Stream connection lost: BrokenPipeError(32, 'Broken pipe')
I tried running the queue listener like this answer as well. Nothing working.
Any one experienced has any thoughts about this? Is there a better way to approach this problem.?
you should move the rabitMQ cosumering logic out of the websocket consumer.
Just have a django command that runs the Rabbit Consumer, that consumer can take messages from RabbitMQ and then use send_group to send them over groups to channels.
if your django command you will need to call send_group see https://channels.readthedocs.io/en/latest/topics/channel_layers.html#using-outside-of-consumers
from channels.layers import get_channel_layer
channel_layer = get_channel_layer()
async_to_sync(
channel_layer.group_send
)(
"user_type_2",
{"type": "message", "msg": 123}
)
Then in the websocket consumer you should subscribe to the groups that the user wants/has permition to get.
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"),
])
Take a look at this example.
As you can see, some sort of event is constantly being sent to the client. I want to imitate this using Django-Channels, inside consumers.py. Here's a simplified version of what I have:
class ChatConsumer(AsyncConsumer):
async def ws_connect(self, event):
self.send = get_db_object()
....
await self.send({
"type": "websocket.accept"
})
# I need to CONSTANTLY receive & send data
async def ws_receive(self, event):
obj = ...# query DB and get the newest object
json_obj = {
'field_1': obj.field_1,
'field_2': obj.field_2,
}
await self.send({
"type": "websocket.send",
"text": json.dumps(json_obj)
})
#database_sync_to_async
def get_db_object(self, **kwargs):
return Some_Model.objects.get(**kwargs)[0]
Here, I want my Django backend to constantly:
Query DB
Receive obj from DB
Send the received obj to Front-End WebSocket as event
How can I achieve this? The important thing is that I need to CONSTANTLY send data to the client.
Most of the Django-Channels resources on the internet cover only Chat Apps, which don't necessarily constantly send data to the client. I couldn't find any working code that does this job.
Please, no more recommendation for Redis or channels documentation... or some random 3rd party libraries that lacks good documentation... It's easy to recommend but hard to implement. For example, I found someone recommending Snorky, but it really lacks documentation on how to implement it.
However, if there's a website that specifically does this job, I might take a look at it, even if it doesn't use Django-Channels.
consumers.py
import asyncio
from channels.consumer import AsyncConsumer
class ChatConsumer(AsyncConsumer):
async def websocket_connect(self, event):
self.connected = True
print("connected", event)
await self.send({
"type": "websocket.accept"
})
while self.connected:
await asyncio.sleep(2)
obj = # do_something (Ex: constantly query DB...)
await self.send({
'type': 'websocket.send',
'text': # obj,
})
async def websocket_receive(self, event):
print("receive", event)
async def websocket_disconnect(self, event):
print("disconnected", event)
self.connected = False
Javascript
var loc = window.location;
var wsStart = 'ws://';
if (loc.protocol == 'https:') {
wsStart = 'wss://'
}
var endpoint = wsStart + loc.host + loc.pathname;
var socket = new WebSocket(endpoint);
socket.onmessage = function(e){
console.log("message", e);
};
socket.onopen = function(e){
console.log("open", e);
};
socket.onerror = function(e){
console.log("error", e)
};
socket.onclose = function(e){
console.log("close", e)
};
All you need to do is just modify obj and send it. You can extend this function as much as you want. So, right now I'm interested in getting the latest inserted row in my PostgreSQL and injecting that row into my WebSocket. I can query my DB every 2 seconds as it was specified by await asyncio.sleep(2), and inject it into the Front-End socket.
Using channels==1.* and Django==1.* you can use the threading module for example:
# Some view.py
import threading
import time
class Publisher(threading.Thread):
def __init__(self, reply_channel, frequency=0.5):
super(Publisher, self).__init__()
self._running = True
self._reply_channel = reply_channel
self._publish_interval = 1.0 / frequency
def run(self):
while self._running:
self._reply_channel.send({'text': 'some data'})
time.sleep(self._publish_interval)
def stop(self):
self._running = False
publishers = {}
def ws_connect(message):
message.reply_channel.send({'accept': True})
publisher = Publisher(reply_channel=message.reply_channel)
publisher.start()
publishers[message.reply_channel] = publisher
def ws_disconnect(message):
publisher = publishers[message.reply_channel]
publisher.stop()
del publishers[message.reply_channel]
A little late to the party here, but when it comes to Django you should always try to do things "their way" first...
So, to do this I simply used Django Channels. My client sends a message to the server, which the server then responds to with the needed database info. It looks as follows:
class SettingsConsumer(WebsocketConsumer):
def connect(self):
self.accept()
def disconnect(self, close_code):
pass
def receive(self, text_data):
settings = get_settings(self.scope["user"])
self.send(
text_data=json.dumps(
{
"playMode": settings.play_mode,
"isRecording": settings.is_recording,
}
)
)
Now, as for the JS to trigger constant events... I simply use SetInterval to request updates from the consumer every .25s!
My logic is that it's the client so if it's doing a little extra work no biggie, as the server is gonna be responding anyways. The JS looks as follows...
const chatSocket = new WebSocket(
'ws://'
+ window.location.host
+ '/ws/macros/update/'
);
chatSocket.onmessage = function(e) {
const data = JSON.parse(e.data);
if(data["playMode"] == true) {
$('#playmode-checkbox').attr('checked', true);
} else {
$('#playmode-checkbox').attr('checked', false);
}
if(data["isRecording"] == true) {
$('#recording-checkbox').attr('checked', true);
} else {
$('#recording-checkbox').attr('checked', false);
}
};
chatSocket.onclose = function(e) {
console.error('Chat socket closed unexpectedly');
};
window.setInterval(function() {
chatSocket.send(JSON.stringify({
'message': "start"
}));
}, 250);
And yes, you can do more to make this more async-friendly and optimized. But, you asked for simple and working so I hope this helps!