unable to find "application" callable in file /app/webapp.py

I am converting a flask application to Docker using uwsgi-nginx-flask-docker. I am using flask_restful to support a restful interface only.

Here are the relevant parts of my webapp.py (equivalent of main.py in the example):

#!flask/bin/python
import os, sys; sys.path.append(os.path.dirname(os.path.realpath(__file__)))
from flask import Flask, jsonify, make_response
from flask_restful import Api
from flask_cors import CORS
from actual_app.frontend import resources, useradmin, entityadmin
from flask_jwt_extended import JWTManager
import logging, logging.handlers

app = Flask(__name__, static_folder='static', static_url_path='')
app.config['CORS_HEADERS'] = 'Content-Type'

cors = CORS(app, resources={r"/api": {"origins": "http://localhost"}})

logging.basicConfig(level=logging.INFO)

app.debug = True
app.config['SECRET_KEY'] = 'app-is-cool'
app.config['JWT_ACCESS_LIFESPAN'] = {'hours': 24}
app.config['JWT_REFRESH_LIFESPAN'] = {'days': 30}

jwt = JWTManager(app)

api = Api(app)

api.add_resource(resources.Login, '/api/login', methods=['POST'])
api.add_resource(resources.Logout, '/api/logout', methods=['POST'])
api.add_resource(resources.RegisterOtp, '/api/register_otp', methods=['POST'])

...

@app.route('/', methods=['POST', 'GET'])
def index():
    return "<h1>Example Limited</h1>"

@app.errorhandler(404)
def not_found(error):
    return make_response(jsonify({'error': 'Not found'}), 404)

@app.errorhandler(500)
def server_error(e):
    logging.exception('An error occurred during a request. %s', e)
    return "An internal error occurred", 500

if __name__ == '__main__':
    app.run(host='0.0.0.0', debug=True, port=80, use_reloader=False)

I run it as docker run --name app_name -d -e URL=http://localhost -e EMAIL=Dev -e CLIENT=dev -e CACHE="1 Month" -v /datanew:/datanew -p 80:80 --rm myapp/web:v01

I have the Flask application named ‘app’ as required but get this error:

unable to find "application" callable in file /app/webapp.py
unable to load app 0 (mountpoint='') (callable not found or import error)
*** no app loaded. GAME OVER ***

Ideas on what might be wrong?

[tiangolo]

The problem is that the image is not being able to find your Flask app. The module in this case is webapp, by the error, it seems you seem to have that correctly set. But the callable is not application, but app. The callable is the variable with the Flask app.

Check the docs here: https://github.com/tiangolo/uwsgi-nginx-flask-docker#custom-uwsgiini-configurations

This is what I think your /app/uwsgi.ini file should look like:

[uwsgi]
module = webapp
callable = app

---

About migrating to FastAPI, I guess that code could look like:

@app.post("/register_otp/")
def register_OTP(user = Depends(get_current_user), email: str = Body(..., embed=True)):
    url = pyqrcode.create(user.get_totp_uri(users_file))
    users_cache.update(email, user, users_file)
    stream = BytesIO()
    url.svg(stream, scale=5)
    return {'register_otp': base64.b64encode(stream.getvalue()).decode()}

That would expect a JSON like:

{"email": "[e-mail]"}

And the dependency get_current_user would be re-usable and would extract the JWT as described here: https://fastapi.tiangolo.com/tutorial/security/oauth2-jwt/

If you want to separate all the HTTP methods for /register-otp/, you could put them in a single Python file (a Python module), with a “router”, and then include them using the prefix URL /register_otp.

In that case, that would look like:

from fastapi import FastAPI, Body, Depends


@app.post("/")
def register_OTP(user = Depends(get_current_user), email: str = Body(..., embed=True)):
    url = pyqrcode.create(user.get_totp_uri(users_file))
    users_cache.update(email, user, users_file)
    stream = BytesIO()
    url.svg(stream, scale=5)
    return {'register_otp': base64.b64encode(stream.getvalue()).decode()}

Notice the @app.post("/") without /register_otp/.

And your docs would look like:

[tiangolo]

Great! Thanks for reporting back and closing the issue.