How to Deploy Flask App on Droplets

Hey!

Great job on getting your Flask app running on a DigitalOcean Droplet! To ensure your app stays online 24/7 and to set up a subdomain pointing to it, you’ll need to follow a few important steps.

To keep your app running continuously, especially after closing the terminal or in case of errors, using a process manager like Gunicorn is crucial. Moreover, integrating Gunicorn with systemd allows your Flask app to auto-start on boot and restart in case it crashes. Let’s set this up:

1. Install Gunicorn:

   pip3 install gunicorn
   

2. Test Run Gunicorn: First, ensure Gunicorn can serve your Flask app correctly. Replace main:app with your file and application name.

   gunicorn --workers 3 --bind unix:myapp.sock -m 007 main:app
   

   Here, main:app indicates that your Flask application instance is named app and is located in the main.py file. The command starts your app with 3 worker processes, using a Unix socket for communication, which is both efficient and secure.

3. Create a systemd Service File for Your App: Next, create a systemd service file to manage your app. Create a new file named /etc/systemd/system/yourapp.service with the following content:

   [Unit]
   Description=Gunicorn instance to serve your Flask app
   After=network.target
   
   [Service]
   User=your_user
   Group=www-data
   WorkingDirectory=/var/www/your_project
   Environment="PATH=/var/www/your_project/venv/bin"
   ExecStart=/var/www/your_project/venv/bin/gunicorn --workers 3 --bind unix:yourapp.sock -m 007 main:app
   
   [Install]
   WantedBy=multi-user.target
   

   Replace your_user, /var/www/your_project, and other paths as necessary for your setup. This service file tells systemd how to start and manage your Gunicorn process.

4. Enable and Start Your Flask App Service:

   sudo systemctl start yourapp.service
   sudo systemctl enable yourapp.service
   

   These commands start the service and enable it to start on boot, respectively.

5. Configure Nginx to Proxy Requests to Gunicorn: Update your Nginx configuration to proxy requests to the Gunicorn socket as described in the previous message. Make sure to adjust the proxy_pass directive to point to the correct socket file path.

You can also follow a more in-depth guide on how to do that here:

https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-22-04

For the subdomain setup, the process remains the same. Ensure your DNS A record points to the Droplet’s IP, configure Nginx with your subdomain, and consider securing it with an SSL certificate using Let’s Encrypt:

https://www.digitalocean.com/community/tutorials/how-to-create-a-self-signed-ssl-certificate-for-nginx-in-ubuntu-22-04#step-2-–-configuring-nginx-to-use-ssl

Hope that this helps and happy coding and deployment!

Best,

Bobby

Heya @fa452710b73e4632997145b18bc820,

First, you’ll need to configure Nginx to run as a reverse proxy so that you don’t have to call the port by only the IP or your domain to open the flask app:

https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-20-04

In the tutorial you’ll see how to configure your Flask app with Nginx and Gunicorn. Which should do the trick for you and keep the app online 24/7

Alternatively, you can take a look at pm2. You can check that tutorial and while it’s for nodeJS, it can easily be done with your flask app as well:

https://www.digitalocean.com/community/tutorials/how-to-use-pm2-to-setup-a-node-js-production-environment-on-an-ubuntu-vps

Anyway, the standard approach is using the first article I gave you.