I got quart websocket example running on Python 3.6.4. Now I want to read data from a

reading from redis queue and sending data to webpage about quart HOT 4 CLOSED

juntiedt2 commented on July 18, 2024

reading from redis queue and sending data to webpage

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Comments (4)

pgjones commented on July 18, 2024

I think splitting this into producing and consuming tasks makes sense, although I'm not sure. Does this work and make sense to you? I think it is the right idea.

@copy_current_websocket_context
async def send():
    while True:
        data = await aioredis.receive()
        await websocket.send(data)

@copy_current_websocket_context
async def receive():
    while True:
        data = await websocket.receive()
        await aioredis.send(data)

@app.websocket('/')
async def index():
    sender = asyncio.ensure_future(send())
    receiver = asyncio.ensure_future(receive())
    gathered = asyncio.gather(sender, receiver)
    try:
        await gathered
    except CancelledError:  # Is raised when websocket connection closes
        gathered.cancel()

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juntiedt2 commented on July 18, 2024

Hi Phil, thank you very much! Yes, it looks very good. I found a similar example on the websockets page but did not know how to put it into Quart. I tried to solve the problem with different namespaces – actually one websocket for sending and another for receiving, but yours looks much better. Regards Hannes Von: Phil Jones <[email protected]> Gesendet: Donnerstag, 1. März 2018 21:26 An: pgjones/quart <[email protected]> Cc: juntiedt2 <[email protected]>; Author <[email protected]> Betreff: Re: [pgjones/quart] reading from redis queue and sending data to webpage (#10) I think splitting this into producing and consuming tasks makes sense, although I'm not sure. Does this work and make sense to you? I think it is the right idea. @copy_current_websocket_context async def send(): while True: data = await aioredis.receive() await websocket.send(data) @copy_current_websocket_context async def receive(): while True: data = await websocket.receive() await aioredis.send(data) @app.websocket('/') async def index(): sender = asyncio.ensure_future(send()) receiver = asyncio.ensure_future(receive()) gathered = asyncio.gather(sender, receiver) try: await gathered except CancelledError: # Is raised when websocket connection closes gathered.cancel() — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://github.com/pgjones/quart/issues/10#issuecomment-369719961> , or mute the thread <https://github.com/notifications/unsubscribe-auth/Aig1jHssEP4ycwcYg2Q_81IgLBGET2zyks5taFlzgaJpZM4SWpCP> . <https://github.com/notifications/beacon/Aig1jCb2qe9WUqp44p6IBnwKSidoE_pEks5taFlzgaJpZM4SWpCP.gif>

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juntiedt2 commented on July 18, 2024

I tried the following code together with your example Quart echo web page.
Receiving data from redis queue and sending it to the webpage works ok. But receiving data from the webpage does not work. Why?

from quart import Quart, render_template, websocket
from RedisQueue import RedisQueue

app = Quart(__name__)
q_in = RedisQueue('ws_2')
q_out = RedisQueue('ws_3')

async def aioredis_receive():
    #return q_in.get()
    return q_in.get().decode("utf-8")
    
async def aioredis_send(data):
    q_out.put(data)    

@app.route('/')
async def index():
    return await render_template('index.html')

@app.websocket('/ws')
async def send():                        #send to Web-Page
    while True:
        data = await aioredis_receive()
        print("From redis queue: ", data)
        await websocket.send(data)

@app.websocket('/ws')
async def receive():                     #receive from Web-Page
    while True:
        data = await websocket.receive()
        print("From Web-Page: ", data)
        await aioredis_send(data)

@app.websocket('/ws')
async def ws():
    sender = asyncio.ensure_future(send())
    receiver = asyncio.ensure_future(receive())
    gathered = asyncio.gather(sender, receiver)
    try:
        await gathered
    except CancelledError:  # Is raised when websocket connection closes
        gathered.cancel()
        
if __name__ == '__main__':
    app.run(port=5000)

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pgjones commented on July 18, 2024

I don't think redis queue is based on asyncio, so it will likely block the event loop. It may work to switch to use asyncio.run_in_executor but I think asyncio-redis is a better choice.

I'm also ensure what happens if you define a route many times (@app.websocket('/ws')), I don't think you need to and I think ~~the last call will overwrite the previous ones~~ only the first one counts.

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