Lets go through step by step tutorial on how to deploy flask app on Ubuntu Server or Google Cloud Platform’s Virtual Machine using Nginx and Gunicorn.
Step 1. Install the required packages
sudo apt updateNow let’s install python3, python3-pip, and Nginx using the commands below:
sudo apt install python3-pip python3-dev nginxStep 2. After installing python, pip and nginx, Create a directory (for our flask app) and virtual environment.
First install virtual environment.
sudo pip3 install virtualenv
mkdir myFlaskApp && cd myFlaskAppRun the following command to create a virtual environment named env.
virtualenv envAnd then activate the virtual environment.
source env/bin/activateNow lets install flask and gunicorn using pip.
pip3 install flask gunicornStep 3. Create a demo project and wsgi entry point
sudo nano app.pyPaste the contents below to app.py file
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return "Hello World!"
if __name__ == '__main__':
app.run(debug=True,host='0.0.0.0')Now, we’ll create a file that will serve as the entry point for our application. This will tell our Gunicorn server how to interact with the application.
sudo nano wsgi.pycopy the contents below to wsgi.py
from app import app
if __name__ == "__main__":
app.run()Install the app requirement
pip install -r requirement.txtnow run the command below:
gunicorn --bind 0.0.0.0:5000 wsgi:appThis was just to test the app is running or not. Now lets deactivate our virtual environment now:
deactivateStep 4. Creating a systemd service
sudo nano /etc/systemd/system/app.serviceNow paste the contents below to this file:
[Unit]
# specifies metadata and dependencies
Description=Gunicorn instance to serve myproject
After=network.target
# tells the init system to only start this after the networking target has been reached
# We will give our regular user account ownership of the process since it owns all of the relevant files
[Service]
# Service specify the user and group under which our process will run.
User=osmlist
# give group ownership to the www-data group so that Nginx can communicate easily with the Gunicorn processes.
Group=www-data
# We'll then map out the working directory and set the PATH environmental variable so that the init system knows where our the executables for the process are located (within our virtual environment).
WorkingDirectory=/home/osmlist/myFlaskApp/
Environment="PATH=/home/osmlist/myFlaskApp/env/bin"
# We'll then specify the commanded to start the service
ExecStart=/home/osmlist/myFlaskApp/env/bin/gunicorn --workers 3 --bind unix:app.sock -m 007 wsgi:app
# This will tell systemd what to link this service to if we enable it to start at boot. We want this service to start when the regular multi-user system is up and running:
[Install]
WantedBy=multi-user.targetActivate this service with the command below:
sudo systemctl start app
sudo systemctl enable appA file named app.sock will be automatically created.
Step 5. Configuring Nginx
Create a file named app inside /etc/nginx/sites-available
sudo nano /etc/nginx/sites-available/appserver {
listen 80;
server_name 172.158.155.154;
location / {
include proxy_params;
proxy_pass http://unix:/home/osmlist/myFlaskApp/app.sock;
}
} Activate this configuration by executing the command below:
sudo ln -s /etc/nginx/sites-available/app /etc/nginx/sites-enabledsudo systemctl restart nginxIf it is not running you may need to go to your firewall settings and allow the port 80 and you should get it work just fine, or just run sudo ufw allow ‘Nginx Full’ command in the server.
You may need to install ufw in some server with sudo apt install ufw and you are good to go.
