A small Python Flask application to generate short links

• Generate short link
• Redirect to original link
• Show all generated links

Build and run the container.

docker build -t krunchly:latest .
docker run -d -p 8000:5000 --rm krunchly:latest

In order to connect to an external database, you can pass your own variables to the docker run command.

docker run -d -p 8000:5000 --rm -e SECRET_KEY=super-secret-key \
        -e DATABASE_URL=mysql+pymysql://<db_user>:<db_password>@<db_host>:<db_port>/<db_name> \
        krunchly:latest

Setup nginx as mentioned below.

These installation steps were done on Ubuntu 18.04 LTS. YMMV on other OS, but the general idea is the same. Basically you need a Python 3 environment, a webserver (I'm using gunicorn and nginx here) and a MySQL database.

sudo apt-get -y update
sudo apt-get -y install python3 python3-venv python3-dev python3-pip
sudo apt-get -y install mysql-server supervisor nginx git

git clone https://github.com/muhannad0/krunch-ly.git
cd krunch-ly
python3 -m venv venv
source venv/bin/activate
(venv) pip3 install -r requirements.txt
(venv) pip3 install gunicorn pymysql

Create .env file in base directory with variables below

SECRET_KEY=super-secret-key
DATABASE_URL=mysql+pymysql://<db_user>:<db_password>@localhost:3306/<db_name>

Export variable for entry point to Flask application

echo "export FLASK_APP=krunchly.py" >> ~/.profile

Login as with root user and create database and user. Remember to update .env file with the correct info used here.

CREATE DATABASE <db_name>;
CREATE USER '<db_user>'@'localhost' IDENTIFIED BY '<db_password>';
GRANT ALL PRIVILEGES ON <db_name>.* to '<db_user>'@'localhost';
FLUSH PRIVILEGES;
QUIT;

Populate the database.

(venv) flask db upgrade

Create a supervisor config to run the app using Gunicorn. Below is a sample configuration.

sudo vi /etc/supervisor/conf.d/krunchly.conf

[program:krunchly]
command=/home/ubuntu/krunch-ly/venv/bin/gunicorn -b localhost:8000 -w 4 krunchly:app
directory=/home/ubuntu/krunch-ly
user=ubuntu
autostart=true
autorestart=true
stopasgroup=true
killasgroup=true

Reload supervisor service for new config to be loaded

sudo supervisorctl reload

We will be deploying it as the only HTTP site on the server. To start we'll remove the default config.

sudo rm /etc/nginx/sites-enabled/default

Create a new virtualhost for our application.

sudo vi /etc/nginx/sites-available/krunchly

server {
    listen 80;
    server_name _;

    location / {
        proxy_pass http://localhost:8000;
        proxy_redirect off;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

    access_log /var/log/nginx/krunchly_access.log;
    error_log /var/log/nginx/krunchly_error.log;
}

Create a symlink to enable the virtualhost.

sudo ln -s /etc/nginx/sites-available/krunchly /etc/nginx/sites-enabled/krunchly

Reload nginx service.

sudo systemctl reload nginx

You should now be able to access the app from the browser.

Mohamed Muhannad (@monde_)

• The Flask Mega-Tutorial by Miguel Grinberg