RuntimeError: There is no current event loop in thread

[summersz]

I have implemented the examples into a Flask api but receive the following error: RuntimeError: There is no current event loop in thread 'Thread-3'

It seems that get_event_loop() will only create a new event loop if it is running on the main thread. Is there a reason that the event loop is created like this rather than using asyncio.run()?

Alternatively, can the event loop be created using the following:

loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

I am unfamiliar with asyncio and am not sure what the ramifications are of using either option.

[serhiibuniak-okta]

@summersz Could you please, provide more details, maybe share some code or post some instructions what and when it happens, etc.?

Upd: asyncio.run() - introduced in Python3.7, you can use it. But if someone need to make it working with Python3.6+, then should use given approach

[summersz]

Thanks @serhiibuniak-okta. I have the below module to create a decorator that is called on protected routes. The error is thrown when a request is made to a protected route. I am using Python 3.7 so will proceed with using asyncio.run().

import asyncio
from flask import current_app, request
from okta_jwt_verifier import JWTVerifier
from functools import wraps

class JWTBaseException(Exception):
    pass

class NoAuthorizationError(JWTBaseException):
    pass

loop = asyncio.get_event_loop()

def token_required(f):
    @wraps(f)
    def wrapper(*args, **kwargs):
        try:
            verify_token()
        except:
            return "Unauthorized", 401
        return f(*args, **kwargs)
    return wrapper

def verify_token():
    if request.method == 'OPTIONS':
        return
    try:
        token = request.headers.get("Authorization").split("Bearer ")[1]
    except:
        raise NoAuthorizationError
    try: 
        is_access_token_valid(token) 
    except NoAuthorizationError:
        raise

def is_access_token_valid(token):
    jwt_verifier = JWTVerifier(current_app.config['OKTA_ISSUER'],current_app.config['OKTA_CLIENT_ID'], current_app.config['OKTA_AUDIENCE'])
    try:
        loop.run_until_complete(jwt_verifier.verify_access_token(token))
        # asyncio.run(jwt_verifier.verify_access_token(token))
        return
    except Exception:
        raise NoAuthorizationError

Traceback (most recent call last):
  File "C:\Users\summersra\Python\AutopilotAPI\AutopilotAPI\__init__.py", line 4, in <module>
    from AutopilotAPI.routes import initialize_routes
  File "C:\Users\summersra\Python\AutopilotAPI\AutopilotAPI\routes.py", line 3, in <module>
    from .Resources.CHK.BFM import *
  File "C:\Users\summersra\Python\AutopilotAPI\AutopilotAPI\Resources\CHK\BFM.py", line 1, in <module>
    from AutopilotAPI.okta_auth import token_required
  File "C:\Users\summersra\Python\AutopilotAPI\AutopilotAPI\okta_auth.py", line 12, in <module>
    loop = asyncio.get_event_loop()
  File "C:\Python38\Lib\asyncio\events.py", line 639, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
RuntimeError: There is no current event loop in thread 'Thread-3'.

[serhiibuniak-okta]

@summersz , usually, this kind of error happens, when no event loop is started. It would be good to see full code, but looks like the problem is in "token_required" function, from this doc https://flask.palletsprojects.com/en/2.0.x/async-await/ it should be like the following:

def extension(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        ...  # Extension logic
        return current_app.ensure_sync(func)(*args, **kwargs)

    return wrapper

A bit another approach how to handle async code, you can find within these samples https://github.com/okta/samples-python-flask

Let me know if anything helps. Otherwise, it would be good to see the whole code (without any sensitive info, of course) and I'll be able to help more.

[serhiibuniak-okta]

@summersz I'm closing this issue as stalled. Feel free to reopen this issue or create a new one if your problem exists still.