In this episode of Running in Production, Francisco Barcena goes over building an internal food order processing system for the city of Los Angeles, CA with Flask and Python. It’s hosted on a single DigitalOcean server and has been up and running since 2016.

Francisco talks about developing a freelance project for a client as a solo developer, scraping the USDA’s site, working with Flask-SocketIO to create a real-time ordering service and getting everything up and running on a single server without using Docker, CI or configuration management tools.

Topics Include

• 3:15 – Replacing spreadsheets with a web app as the single dev on this project
• 4:12 – It was better off making a hand rolled solution instead of using an existing platform
• 5:08 – Motivation for using Flask instead of Django and other frameworks
• 5:56 – It’s a single monolithic app that was built up in phases / stages
• 6:20 – The Scrapy library is used to scrape CSV links from the USDA site
• 7:01 – The app uses server rendered Jinja 2 templates with a few ajax calls
• 8:35 – Websockets with Flask-SocketIO is used to provide a real time order placing page
• 11:28 – Caching some of the daily values with Flask-Cache
• 12:48 – SQLAlchemy with PostgreSQL is used for the database back-end
• 12:59 – Tracking down database session issues by disabling an accidental DEBUG flag
• 13:59 – gunicorn is being used as the Flask app server
• 14:21 – DigitalOcean is being used to host the app
• 15:15 – Docker isn’t being used at the moment since he didn’t know about it ~3 years ago
• 17:52 – The DigitalOcean server has 1 GB of memory and 2 CPU cores
• 19:05 – Ubuntu 16.04 LTS is the Linux distro being run on the server
• 19:24 – Configuration of the server was done by hand
• 20:14 – Process management is done with a “YOLO but call me” strategy
• 21:21 – nginx is set up with Let’s Encrypt and Certbot to secure the site over HTTPS
• 21:53 – nginx is also used to serve static files (images, CSS, etc.) directly
• 22:17 – Flask-Mail is used to send out emails such as password passwords
• 23:06 – The app itself doesn’t handle payments in real time, it takes food orders
• 23:46 – The deployment process is to push to BitBucket and pull it from the server
• 24:16 – Secret values aren’t in version control
• 24:53 – There’s no automated tests, but things are extensively tested by the few end users
• 26:55 – The server and data is backed up daily with DigitalOcean’s droplet backup feature
• 28:21 – Best tips? Have automated tests for your code base
• 30:40 – Find a bunch of info about Francisco on his personal site (also built in Flask)

Links

• https://scrapy.org/
• https://www.usda.gov/
• https://en.wikipedia.org/wiki/Linear_regression
• https://www.postgresql.org/
• https://nginx.org/en/
• https://github.com/certbot/certbot

• flask →
• python →
• digitalocean →
• lets-encrypt →
• nginx →
• postgres →
• ubuntu →
• websockets →

• https://www.chartjs.org/
• https://github.com/miguelgrinberg/Flask-SocketIO
• https://github.com/thadeusb/flask-cache
• https://gunicorn.org/
• https://www.sqlalchemy.org/
• https://github.com/mattupstate/flask-mail

Support the Show

This episode does not have a sponsor and this podcast is a labor of love. If you want to support the show, the best way to do it is to purchase one of my courses or suggest one to a friend.

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