push with python + asyncio + websockets = missing messages

Question

I'm trying to create a websocket server on which a single client will push its messages (I know this is not the usual way to use websocket but this part is not my choice). To this end, I'm using python 3.7 and websockets 7.0.

My issue is: Numerous messages pushed by the client are not received by the server. Here is the simple code I'm using.

import asyncio
import websockets


async def get_tag_data(websocket, path):
    # print('received')
    data = await websocket.recv()
    print(data)


loop = asyncio.get_event_loop()
anchors_server = websockets.serve(get_tag_data, 'localhost', 9001)
loop.run_until_complete(asyncio.gather(anchors_server))
loop.run_forever()

Conversely, when I try the python-websocket-server (which uses threads for reception), all my messages are correctly received.

As far as I understand asyncio & websockets, it is supposed to manage backpressure: messages sent while the server is busy (to process older messages) are "buffered" and will be treat shortly....

What am I missing? Do I need to thread the websocket reception with asyncio to avoid losing messages?

Thank you for your answers!

miotani · Accepted Answer · 2019-01-22 15:16:10Z

1

Ok, I get it. My function was running only once, next messages was not buffered. The following code resolve the issue :

import asyncio
import websockets
import signal
import sys

async def get_tag_data(websocket, path):
    while True:
        async for data in websocket:
            print(data)

loop = asyncio.get_event_loop()
anchors_server = websockets.serve(get_tag_data, '', 9001)
loop.run_until_complete(asyncio.gather(anchors_server))
loop.run_forever()

note the

while True:
    async for data in websocket

edited Jan 22, 2019 at 15:16

answered Jan 10, 2019 at 13:12

miotani

115 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Darkhan ZD · Accepted Answer · 2021-09-23 05:09:04Z

1

Shoud be without while loop.

import asyncio
import websockets
import signal
import sys

async def get_tag_data(websocket, path):
    async for data in websocket:
        print(data)

answered Sep 23, 2021 at 5:09

Darkhan ZD

6209 silver badges16 bronze badges

Collectives™ on Stack Overflow

push with python + asyncio + websockets = missing messages

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related