Flask App Deployment: Internal Server Error

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I recently tried to deploy a flask app using Heroku. However, I encountered an internal server error. My code can be found here: https://github.com/chaneth8/Task_List. This is the message that appeared on my log in Heroku - what could the error be?

2021-08-11T08:45:22.861047+00:00 app[web.1]:     return fn(*args, **kwargs)
2021-08-11T08:45:22.861047+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/create.py", line 522, in create_engine
2021-08-11T08:45:22.861047+00:00 app[web.1]:     entrypoint = u._get_entrypoint()
2021-08-11T08:45:22.861048+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/url.py", line 636, in _get_entrypoint
2021-08-11T08:45:22.861048+00:00 app[web.1]:     cls = registry.load(name)
2021-08-11T08:45:22.861048+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/util/langhelpers.py", line 343, in load
2021-08-11T08:45:22.861048+00:00 app[web.1]:     raise exc.NoSuchModuleError(
2021-08-11T08:45:22.861049+00:00 app[web.1]: sqlalchemy.exc.NoSuchModuleError: Can't load plugin: sqlalchemy.dialects:postgres
2021-08-11T08:45:22.862035+00:00 app[web.1]: 10.1.24.101 - - [11/Aug/2021:08:45:22 +0000] "GET /main HTTP/1.1" 500 290 "https://evening-sands-15945.herokuapp.com/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36"
2021-08-11T08:45:22.862177+00:00 heroku[router]: at=info method=GET path="/main" host=evening-sands-15945.herokuapp.com request_id=4bc8206e-cdb1-4d4b-8cc4-05122855e894 fwd="58.177.96.125" dyno=web.1 connect=0ms service=17ms status=500 bytes=539 protocol=https

Thanks in advance.

flask heroku sqlalchemy python
2 Answers

I studied your code and hosted the same on https://ethan-flask.herokuapp.com/

The blunders you did:

from flask_session import Session - remove this

Session(app) - remove this

And add the following code at the end -

if __name__ == "main":
    app.run(port=8000)

I will create a PR on your repo soon Thanks ;)

user_148606030

Any error in your code will reflect upon your application, even after you have hosted your web app.

Try:

  • Looking for any errors in your code.
  • Debugging your code(there is a specific debugger for flask if you're using vs code, or you can set the flask mode to DEBUG (debug=True))
  • Make sure that you packed up the code correctly for Heroku deployment.
user_166382870
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