[Python + Flask] Gunicorn and its famous "sys.exit(run())" message!

[aldolammel]

Hello there.

I’m having a tough time in my first time with Render services (Web application with Python + Flask). Here is the application on Github: https://github.com/abcoo-ideias/portfolio

I’m trying to fix Gunicorn error messages. Check this out:

INFO==> Deploying...
INFO==> Using Node version 20.11.1 (default)
INFO==> Docs on specifying a Node version: https://render.com/docs/node-version
INFO==> Running 'gunicorn app:app'
INFOTraceback (most recent call last):
INFO  File "/opt/render/project/src/.venv/bin/gunicorn", line 8, in <module>
INFO    sys.exit(run())
INFO             ^^^^^
INFO  File "/opt/render/project/src/.venv/lib/python3.11/site-packages/gunicorn/app/wsgiapp.py", line 67, in run
INFO    WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
INFO  File "/opt/render/project/src/.venv/lib/python3.11/site-packages/gunicorn/app/base.py", line 236, in run
INFO    super().run()
INFO  File "/opt/render/project/src/.venv/lib/python3.11/site-packages/gunicorn/app/base.py", line 72, in run
INFO    Arbiter(self).run()

Locally, everything goes fine, however it doesn’t even run here on Render.

My start command is gunicorn app:app, based on Render Docs to Python+Flask.

Right below, it’s a snippet of my main Python file, called app.py:

from flask import Flask, render_template
from flask_sqlalchemy import SQLAlchemy                            # Install = Flask-SQLAlchemy
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column  # Install = SQLAlchemy
from sqlalchemy import Integer, String                             # Install = SQLAlchemy
from flask_bootstrap import Bootstrap5                             # Install = Bootstrap-Flask
import os
from datetime import date

APP_SECRET_KEY = os.environ["APP_SECRET_KEY"]

# Creating the app:
app = Flask(__name__, template_folder="templates", static_folder="static")
app.config["SECRET_KEY"] = APP_SECRET_KEY
app.jinja_env.finalize = lambda x: x if x is not None else ''  # make the jinja doesn't print out NONE values.
bootstrap = Bootstrap5(app)

You can check online the entire file on GitHub.

Current requirements.txt file:

Flask~=3.0.2
SQLAlchemy~=2.0.27
gunicorn~=21.2.0
Bootstrap-Flask~=2.3.3
Jinja2~=3.1.3

Some light on this topic would be very much appreciated, folks.

Cheers and crossed fingers.

[aldolammel]

I got it! The issue took place in the requirements.txt file.

Before the fix:

Flask~=3.0.2
SQLAlchemy~=2.0.27
gunicorn~=21.2.0
Bootstrap-Flask~=2.3.3
Jinja2~=3.1.3

After the fix:

Flask~=3.0.2
SQLAlchemy~=2.0.27
flask-sqlalchemy~=3.1.1
gunicorn~=21.2.0
Bootstrap-Flask~=2.3.3
jinja2~=3.1.3

Notice that jinja2 was misspelled (me), and flask-sqlalchemy module as ignorated (PyCharm).

The issue got started because I trusted on requirements.txt automatic generation from PyCharm. For some reason, its creation (Main menu >> Tools >> Sync Python Requirements) doesn’t track the necessity of jinja2 and flask-sqlalchemy in my project.

[John_B]

Great, thanks for sharing the solution here as well for everyone to learn!

John B
Render Support, UTC