Flask Cyberpanel

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How to host or Deploy a Flask Python Application on a Cyberpanel Server.
With SMTP::

SMTP DETAILS

FLASK_APP=app
MAIL_SERVER=srv.lintsawa.com
MAIL_PORT=587
MAIL_USE_TLS=true
MAIL_USERNAME=dani@lintsawa.com
MAIL_PASSWORD=MGr3J3qupog3
RECEIVER_EMAIL=devinfo797@gmail.com

In this example, I'll be using Almalinux 8, Python version 3.8.20.

Steps

Step 1: Install Python First. You can refer to Python Section on how to install a specific Python version on your OS.

Step 2: Create a website on Cyberpanel for your Flask App.
For me, I'll be using a subdomain called "cyber-flask.lintsawa.com"

Step 3: Upload your Flask Application to the file manager public_html folder of your created domain.

Step 4: Login to your server via SSH.

Step 5: Create a virtual environment for your application.

python3 -m venv /home/cyber-flask.lintsawa.com/public_html/

Step 6: Activate the virtual environment.

source /home/cyber-flask.lintsawa.com/public_html/bin/activate

Step 7: Install your dependencies
pip install -r requirements.txt

Step 8: Create a WSGI entry point for your Flask app
It can be any file as passenger.py, or wsgi.py or passenger_wsgi.py.

For me I'll create passenger.py file on the root directory of my application.

Inside the file add the line below

Add a passenger.py file as the WSGI entry point for your Flask app

from app import application # Ensure application is defined in app/init.py

You should have something similar or close to this below.

/home/flaskapp.lintsawa.com/public_html/
├── app/
│ ├── init.py
│ ├── routes.py
│ ├── templates/
│ └── static/
├── passenger.py
├── requirements.txt
├── venv/ (virtual environment)

My app/init.py configuration is as below:
NOTE: This section may differ depending on how you've configured your application code. Adjust accordingly.

from flask import Flask
from flask_mail import Mail
from config import Config

mail = Mail()

def create_app():
app = Flask(name)
application = app
app.config.from_object(Config)

mail.init_app(app)

from .routes import main
app.register_blueprint(main)

return app

application = create_app() # Here Define application explicitly for the web server

The key line is: application = create_app().
This ensures application is a globally accessible variable.

If you don't get this part right, you may run into error 500 where you may see error as below.

tail -f /usr/local/lsws/logs/stderr.log
from flask import Flask
ModuleNotFoundError: No module named 'flask'
[UID:65534][248287] packetLen < 0
Traceback (most recent call last):
File "/home/kibe-cyberflask.lintsawa.com/public_html/passenger.py", line 1, in
from app import application
File "/home/kibe-cyberflask.lintsawa.com/public_html/app/init.py", line 1, in
from flask import Flask
ModuleNotFoundError: No module named 'flask'
[UID:65534][248287] packetLen < 0
^C

Step 9: Add the context inside vHOST on Cyberpanel.

Ensure you adjust the location, startupFile, and evn to match your application settings.

context / {
type appserver
location /home/cyber-flask.lintsawa.com/public_html
binPath /usr/local/lsws/fcgi-bin/lswsgi
appType wsgi
startupFile passenger.py
envType 1
env LS_PYTHONBIN=/home/cyber-flask.lintsawa.com/public_html/bin/python3
}

Step 10: Do a quick test to confirm your app is loading well.

Check Python Path for Flask

/home/cyber-flask.lintsawa.com/public_html/bin/python3 -m flask --version # This part uses your created virtual env. Get this right.

Test 2
Run passenger.py with Virtual Environment
Manually run the application using the virtual environment's Python binary:

/home/cyber-flask.lintsawa.com/public_html/bin/python3 passenger.py
No output should be displayed indicating all is working well.

Step 11: Restart your webserver - In this case, restart openlitespeed.

/usr/local/lsws/bin/lswsctrl restart

Step 11: Load your domain and it should be accessible online.

For me I did not have a home page thus the 404 error on home. But I had a route at /contact.

Troubleshooting.

Use command below to check for error messages and fix them.

tail -f /usr/local/lsws/logs/stderr.log

All Done!!

Flask Cyberpanel

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