[Python] Flask-Socketio not emitting in worker thread

I have a program with a queue and a worker thread that executes everything in the queue. When the thread is done processing a job, it should emit some data. It says it is emitting, but the client side doesn't receive the message. When I emit something using the exact same command in the test endpoint, it does work.

from flask import Flask, render_template, request, session
from flask_socketio import SocketIO, emit
from threading import Thread
from queue import Queue
import time

app = Flask(__name__)
socketio = SocketIO(app, engineio_logger=True, logger=True, cors_allowed_origins="*")
job_queue = Queue()

def worker():
while True:
sid, job = job_queue.get()
if job is None:
break

print(f"Processing {job}", flush=True)
time.sleep(2)


socketio.emit("response", {"filename": job}, to=sid)
print(f"Emitted response to {sid}", flush=True)

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

@app.route("/test", methods=["POST"])
def test():
sid = request.args.get('sid')
job_queue.put((sid, "test"))
socketio.emit("response", {"filename": "test"}, to=sid)
return "OK", 200

@socketio.on('connect', namespace='/')
def connected():
print("Connected", flush=True)

if __name__ == '__main__':
Thread(target=worker, daemon=True).start()
socketio.run(app, debug=True)


I have added the sid as a parameter to the emit because clients are given a room with their sid name. Like this, I can get past the socketio emitting out of scope error.

I have also tried to use socketio.start_background_task(), but this didn't work either.

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