[FIXED] Flask on Heroku: failed to find attribute <app_name> in run script: error H10 desc="App crashed"

Issue

This is my first (proper) flask app and is essentially an extension of the Corey Schafer Flask YouTube tutorials.

Root folder:

Procfile:

web: gunicorn --bind 0.0.0.0:$PORT run:bsstg

run.py:

from bsstg import create_app

app = create_app()

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

bsstg folder:

Full error listing:

2021-08-21T14:57:45.224522+00:00 heroku[web.1]: State changed from starting to up
2021-08-21T14:57:47.689647+00:00 app[web.1]: /app/.heroku/python/lib/python3.9/site-packages/flask_sqlalchemy/__init__.py:872: FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True or False to suppress this warning.
2021-08-21T14:57:47.689676+00:00 app[web.1]: warnings.warn(FSADeprecationWarning(
2021-08-21T14:57:47.691540+00:00 app[web.1]: /app/.heroku/python/lib/python3.9/site-packages/flask_sqlalchemy/__init__.py:872: FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True or False to suppress this warning.
2021-08-21T14:57:47.691542+00:00 app[web.1]: warnings.warn(FSADeprecationWarning(
2021-08-21T14:57:48.011870+00:00 app[web.1]: Failed to find attribute 'bsstg' in 'run'.
2021-08-21T14:57:48.012140+00:00 app[web.1]: [2021-08-21 14:57:48 +0000] [8] [INFO] Worker exiting (pid: 8)
2021-08-21T14:57:48.012928+00:00 app[web.1]: Failed to find attribute 'bsstg' in 'run'.
2021-08-21T14:57:48.013176+00:00 app[web.1]: [2021-08-21 14:57:48 +0000] [7] [INFO] Worker exiting (pid: 7)
2021-08-21T14:57:48.130969+00:00 app[web.1]: [2021-08-21 14:57:48 +0000] [4] [INFO] Shutting down: Master
2021-08-21T14:57:48.131000+00:00 app[web.1]: [2021-08-21 14:57:48 +0000] [4] [INFO] Reason: App failed to load.
2021-08-21T14:57:48.194499+00:00 heroku[web.1]: Process exited with status 4
2021-08-21T14:57:48.281397+00:00 heroku[web.1]: State changed from up to crashed
2021-08-21T14:57:55.591575+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=bsstg.herokuapp.com request_id=3418126a-a6f6-4e31-93c9-0c688104f8e3 fwd="109.153.222.121" dyno= connect= service= status=503 bytes= protocol=https
2021-08-21T14:57:56.000370+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=bsstg.herokuapp.com request_id=c9360a07-edaa-4857-b5d6-4dcd445adbf7 fwd="109.153.222.121" dyno= connect= service= status=503 bytes= protocol=https

The error

Failed to find attribute 'bsstg' in 'run'"

(bsstg is the name of my app and folder where it exists) is what I have used as the title of the question but maybe this has been leading me around in circles. Two days on this now so any pointers greatly appreciated.

Solution

Your Procfile is almost certainly wrong:

web: gunicorn --bind 0.0.0.0:$PORT run:bsstg

This runs Gunicorn as a web process (one that accepts incoming HTTP and HTTPS requests). Gunicorn expects a WSGI app as an argument. You are passing in run:bsstg, which tells Gunicorn to run whatever bsstg is in the run module.

That leads to the error you are seeing:

Failed to find attribute 'bsstg' in 'run'

There is no bsstg in run.py; the the WSGI app is called app. Try changing it to

web: gunicorn --bind 0.0.0.0:$PORT run:app

Then commit and redeploy.

Answered By - Chris