when use copy_current_request_context and ThreadPoolExecutor, I got error.

[Alvin4567]

I want to use the main thread's request context in the sub-thread. So I use the decorator copy_current_request_context. But I got an error that <Token var=<ContextVar name='flask.request_ctx' at 0x1067aef90> at 0x106c71280> was created in a different Context.

The weirdest thing is when I debug the code one by one, I will get the expected results sometimes.

This is a simple code.

import random
import string
import requests

from flask import Flask, copy_current_request_context
from concurrent.futures import ThreadPoolExecutor

app = Flask(__name__)

def get_trace_id(number):
    trace_id =  "".join(random.sample(string.ascii_letters, number))
    print(requests.get("https://www.google.com").text)
    return trace_id


@app.route("/")
def hello():
    @copy_current_request_context
    def inner_func(number):
        return get_trace_id(number)

    with ThreadPoolExecutor(20) as executor:
        res_iter = executor.map(inner_func, [1, 2, 3, 4, 5])
    return list(res_iter)


if __name__ == '__main__':
    app.run()

Environment:

• Python version: 3.8.17
• Flask version: 2.3.3

[danderwald]

I am facing the same issue after upgrading flask to v 2.2.5 (python 3.11)

[danderwald]

Interesting.

not working:

    @copy_current_request_context
    def do_something(param):
       pass

    loop.run_in_executor(
        executor,
        do_something
        param
    )

working:

    def do_something(param):
       pass

    loop.run_in_executor(
        executor,
        copy_current_request_context(do_something)
        param
    )

after removing copy_current_request_context as a decorator and call it explicitly, I could not reproduce the behavior until now.

[zschneider]

I'm also encountering this issue, and neither approaches above worked for me. I'm on flask v 2.3.3 on Python 3.11. Were you able to get that to work consistently @danderwald?