Flask-MySQL disconnected after performing a sql operation

-sharp!/env/python
-sharpcoding: utf-8

import socketio
import eventlet
from flask import Flask, jsonify, render_template
from flaskext.mysql import MySQL
import pymysql

sio = socketio.Server(async_mode = "eventlet")
app = Flask(__name__)
app.wsgi_app = socketio.Middleware(sio, app.wsgi_app)
app.config["SECRET_KEY"] = "secret!"
app.config["JSON_SORT_KEYS"] = False

dbConfig = {
    "MYSQL_DATABASE_HOST": "127.0.0.1",
    "MYSQL_DATABASE_DB": "test",
    "MYSQL_DATABASE_USER": "root",
    "MYSQL_DATABASE_PASSWORD": "root1234"
}
for key,val in dbConfig.items():
    app.config[key] = val

@app.route("/")
def hello():
    mysql = MySQL( cursorclass = pymysql.cursors.DictCursor )
    mysql.init_app(app)
    cursor = self.__mysql.get_db().cursor()
    cursor.execute("select id uid,cellphone,nickname,sex,age from tb_user limit 3")
    data = cursor.fetchall()
    return jsonify({"code": 200, "message": "", "data": data})

class MyCustomNamespace(socketio.Namespace):
    def on_connect(self, sid, environ):
        print("New client connected - {sid} ".format(sid = sid))
        sio.emit("reply", {"data": "Connected", "count": 0}, 
            room = sid)

    def on_disconnect(self, sid):
        print("Client disconnected [ {sid} ]".format(sid = sid))

    def on_my_event(self, sid, data):
        self.emit("my_response", data)

    def on_disconnectRequest(self, sid):
        sio.disconnect(sid)

sio.register_namespace(MyCustomNamespace("/test"))

if __name__ == "__main__":
    eventlet.wsgi.server(eventlet.listen(("", 5000)), app)

then start server, to return data the first time you request the home page, but an error will be reported when you request the home page again:

Traceback (most recent call last):
  File "D:\Tools\Python363\lib\site-packages\eventlet\wsgi.py", line 539, in handle_one_response
    result = self.application(self.environ, start_response)
  File "D:\Tools\Python363\lib\site-packages\flask\app.py", line 1997, in __call__
    return self.wsgi_app(environ, start_response)
  File "D:\Tools\Python363\lib\site-packages\engineio\middleware.py", line 49, in __call__
    return self.wsgi_app(environ, start_response)
  File "D:\Tools\Python363\lib\site-packages\flask\app.py", line 1993, in wsgi_app
    ctx.auto_pop(error)
  File "D:\Tools\Python363\lib\site-packages\flask\ctx.py", line 387, in auto_pop
    self.pop(exc)
  File "D:\Tools\Python363\lib\site-packages\flask\ctx.py", line 353, in pop
    self.app.do_teardown_request(exc)
  File "D:\Tools\Python363\lib\site-packages\flask\app.py", line 1879, in do_teardown_request
    func(exc)
  File "D:\Tools\Python363\lib\site-packages\flaskext\mysql.py", line 58, in teardown_request
    ctx.mysql_db.close()
  File "D:\Tools\Python363\lib\site-packages\pymysql\connections.py", line 728, in close
    raise err.Error("Already closed")
pymysql.err.Error: Already closed

ask the bosses, what is the reason for this situation, and then what should I do with it?

Python

Mar.04,2021