Example of a scalable Flask API

This the back-end of the Arborator-Grew redevelopement of the arborator-server.

Useful Resources

Before starting to dive deep in the code, you should refer to these following important resources :

• Flask-RESTx : How to build a restful server with python
• Some Flask good practives : How to use static typing and testing procedure with flask.

Setting the environment config

Create a .flaskenv file with the following config

FLASK_ENV=dev|prod|test

Run the backend

To run the backend we use the docker, the steps of the docker installation are here

• To ensure the communication between the containers of the backend and the frontend we need to create network

docker network create external-network

• Run the container of the backend using docker-compose

docker-compose up --build

Handle keys + auth_config

Ask an admin of Arborator the keys.zip and the auth_config.py, and locate them in (from root)

app/auth/auth_config.py
keys/

Manage the database

If first time, initialize the database

python manage.py seed_db

Type "Y" to accept the message (which is just there to prevent you accidentally deleting things -- it's just a local SQLite database)

Database automatic migration

An migration is set using Flask-Migrate. For the moment this migration should only be done on dev mode.

To enable the migrations run the following commands after the git pull: flask db init The register it and enabling automatic migrations by setting a name (here it is "access migration") flask db migrate -m "access migration." Apply the migration flask db upgrade

This migration adds a table alembic_version in the database in order to track migration history. To display migration history please run flask db history.

Handling superadmin

For adding a superadmin, run the following command

python manage.py add_super_admin --username $username

For removing a superadmin

python manage.py remove_super_admin --username $username

Run the app for local development

In .flaskenv, set the FLASK_ENV to dev and FLASK_APP to wsgi.py

FLASK_ENV=dev
FLASK_APP=wsgi.py

Then, you can run the app with flask and a secured certificate protocole.

flask run --cert=adhoc

We need to specify cert because we use Google and Github credentials login and it required an https connection.

Running tests

To run the test suite, simply pip install it and run from the root directory like so

pip install pytest
pytest

Production

Pulling last changes on prod

1. ssh to server
2. go to backend folder
3. pull latests changes : git pull origin main
4. restart service : sudo systemctl restart arborator-backend.service

Deploy the app in production for the first time

Set the environment

On the server, create the project folder

mkdir /var/www/flask_api_example

In the project folder, create a python virtual environment

python -m venv ven

Install the python packages requirements

pip install -r requirements.txt

In .flaskenv, set FLASK_ENV to prod

FLASK_ENV=prod

Initialize the DB (or paste an existant one)

python migrate.py seed_db

Proxy setting

If needed to, allow the folder access to the server user that will have control the app

sudo chown -Rf <admin>:<group> /var/www/flask_api_example/

Debugging and logging

To see the arborator logs :

tail -f /var/log/arborator-backend/arborator-backend.log

To see tge nginx logs :

sudo tail -f /var/log/nginx/access.log

To see all last commands run on the server :

history

source : https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-uswgi-and-nginx-on-ubuntu-18-04

Navigate to the posted URL in your terminal to be greeted with Swagger, where you can test out the API.