Run async functions with Python + Flask application

Help
1

Hey!

I need to run asynchronous functions in my Python + Flask application for a Slack app, which requires a response within 3 seconds while allowing longer processing.

I tried everything that Vercel’s AI suggested + other things I found online like:

  • Using from concurrent.futures import ThreadPoolExecutor
  • Using import threading
  • Using Flask-Executor

The last one gave me this error:

RuntimeWarning: coroutine 'test_async' was never awaited
executor.submit(test_async(command))

And a mix of async python packages, in all of them the function ends as soon as I return on the request.

I saw that there is a waitUntil function in JS, but I didn’t find anything like that for python.

This is the code I’m testing:

@app.route('/slack/commands', methods=['POST'])
async def handle_commands():
    if not signature_verifier.is_valid_request(request.get_data().decode('utf-8'), request.headers):
        return jsonify({'status': 'invalid_request'}), 403

    # Acknowledge Slack's command immediately to avoid timeouts
    command = request.form
    executor.submit(test_async(command))

    # Return an immediate acknowledgment to Slack to avoid timeout
    return jsonify("We are finding your stuff, give us a moment :grimacing:"), 200


async def test_async(command):
    response_url = command.get('response_url')
    try:
        requests.post(response_url, json={"text": "Hello, World!", "response_type": "in_channel",})

        # Simulate some long-running task
        await asyncio.sleep(10)
        
        requests.post(response_url, json={"text": "Waiting for 10 seconds!", "response_type": "in_channel",})
    except Exception as e:
        print(f"Error sending message to response_url: {e}")

(this is a test workflow to test this before we add our core functionality (that takes around 10 seconds) here.

Thanks for your time!

2

Hi, @estefaniarabadan! Welcome to the Vercel Community.

You’re correct that Python doesn’t have a direct equivalent to JavaScript’s waitUntil function. However, we can achieve a similar effect using Python’s asynchronous features. You could maybe try to use the asyncio library along with the aiohttp library for asynchronous HTTP requests?

It’s worth noting that running asynchronous Python applications on Vercel might require some additional configuration. Vercel primarily supports serverless functions, which may have limitations on long-running processes.

Let us know how you get on!

3

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