simple-heroku-mongo-flask-app

A simple Heroku Flask application that connects to MongoDB.

Prerequisites

You will need a Heroku account and the Heroku CLI to run this application. Heroku has a free tier. It is recommended that you follow Heroku's guide to getting started with Python before running this application.

You will also need a MongoDB database to run this application. You can get a free MongoDB database by signing up for MongoDB Atlas. MongoDB Atlas has a free tier which includes a simple cluster deployment.

This README assumes you are running on Linux.

You will need a Python 3 interpreter to run this application. The Python 3 interpreter should include the venv module.

Setup

Python

You will need to create a virtual environment to run this application. Run the following commands at the root of this repo:

python3 -m venv venv
source venv/bin/activate
pip install -Ur requirements.txt

Tell Heroku that you want this repo to be an application:

heroku create

SSL

To preserve consistency with running in the cloud, this application uses HTTPS even when running locally. You will need to run the following commands from the root of the repo to get ready for HTTPS:

mkdir ssl
cd ssl
openssl req -nodes -new -x509 -keyout server.key -out server.crt \
    -subj "/C=GB/ST=London/L=London/O=Local/OU=Local/CN=127.0.0.1"

The ssl folder is ignored by git so you should not need to worry about committing the generated key and certificate.

After generating the key and certificate, you are ready to run the application.

Environment Variables

To run this application, you need to set some environment variables:

• MONGO_USER - The username for the MongoDB connection
• MONGO_PASSWORD - The password for the MongoDB connection
• MONGO_HOST - The host to connect to for the MongoDB connection

Running the application

Local

Your run configuration should look like the following:

venv/bin/gunicorn \
    --certfile=ssl/server.crt \
    --keyfile=ssl/server.key \
    --worker-class eventlet \
    -w 1 \
    "application:create_flask_app()"

Make sure to run the application with the working directory set at the root of the repo.

The webapp should be accessible at https://127.0.0.1:8000

You will most likely need to tell your browser to accept the self-signed certificate.

Heroku Local

After setting up the environment variables, you can run the application locally. Be sure you have activated the virtual environment before running this command:

heroku local

You should then be able to access the application at https://0.0.0.0:5000 in your browser.

You will most likely need to tell your browser to accept the self-signed certificate.

Heroku Cloud

Once you have verified that the application works locally, you can deploy to Heroku:

git push heroku master

Once the deploy succeeds you can spin up a web dynamo to serve requests:

heroku ps:scale web=1

You can use the following command to open the Heroku deployment in your browser:

heroku open

Tests

You can use tox to run the tests in this repo.

First, install tox in the virtual environment:

pip install tox

Next, simply run tox in the root of the repo. In addition to running the unit tests, code linting and formatting will be performed using black, and flake8.

Database

This application creates a database called test. It also creates a collection in that database called test_collection.

This application creates a TTL index on test_collection so documents created by this application will be deleted after some time.