Does the windows environment cause multiple client links to block

[zhenzi0322]

Hello, I am using Flask-SocketIO to process tasks, if a user sends multiple tasks, it will cause the link Flask-SocketIO to block, my environment is windows

[miguelgrinberg]

Flask-SocketIO does not block. My guess is that the tasks that you are running are blocking your server. Or if you are using an asynchronous server (eventlet, gevent) then you are writing blocking tasks that are incompatible with these frameworks.

May I ask you to not write issues on this package when you have a question? There is a discussions board for questions. Thank you.

[miguelgrinberg]

What you do in your task is what will may cause blocking. The start_background_task() always starts background tasks in a way that is compatible with the async framework that you are using.

[zhenzi0322]

What you do in your task is what will may cause blocking. The start_background_task() always starts background tasks in a way that is compatible with the async framework that you are using.

Since there are tasks executing in the background, it blocks the Flask-SocketIO link. Is there any way to make my task not block the Flask-SocketIO link?
Is it possible to use the following startup method to not block the Flask-SocketIO link.

gunicorn -k geventwebsocket.gunicorn.workers.GeventWebSocketWorker -w 1 app:app

Examples：
For example: I open a client A to link Flask-SocketIO, client A sends a hundred tasks to start_background_task for processing, and then I open a new client B. At this point client B blocks, causing Flask-SocketIO to wait for the link.

[miguelgrinberg]

@zhenzi0322 I think you need to familiarize yourself with gevent and learn how concurrency works under this framework. Background tasks should be perfectly fine, as long as they don't block the gevent loop. If you are not familiar with asynchronous development, then my recommendation is that you use the threading concurrency mode, which is based on regular threads and will be easier to manage for you.

[zhenzi0322]

@zhenzi0322 I think you need to familiarize yourself with gevent and learn how concurrency works under this framework. Background tasks should be perfectly fine, as long as they don't block the gevent loop. If you are not familiar with asynchronous development, then my recommendation is that you use the threading concurrency mode, which is based on regular threads and will be easier to manage for you.

Ok, Because I send a message to the foreground via emit after processing a task in the background task. And that's when it causes blocking. The background task itself does not block if it does not send an emit.

Example:

from gevent import monkey

monkey.patch_all()
from gevent.pool import Pool
import random
import time
from config import socketio


def background_thread():
    """start_background_task"""
    p = Pool(size=20)
    count = 0
    while True:
        count += 1
        value = queue.get_wait()
        if value:
            time.sleep(random.randint(2, 8))
            p.spawn(socketio.emit, "result", {"data": "ok"}, to="xxx")

[miguelgrinberg]

I don't understand what the problem is. The emit function is non-blocking, all it does is store the message in a queue and returns. The actual data transfer happens in the background. So I don't see how emit can be blocking. There is also no need to put the emit call in a pool, you can just call socket.emit() directly in the function and you'll get the same result.