Flask + Celery + SQLAlchemy Example App

This example app demonstrates how to write Celery tasks that work with Flask and SQLAlchemy. I had a hard time finding a complete example that worked correctly.

Based on the the Flask-User-Starter-App. Other references :

Code characteristics

Tested on Python 3.10
Well organized directories with lots of comments
- app
  - celeryapp
  - core
  - dashapp
  - oauth
  - rssapp
  - static
  - templates
  - commands.py
  - extensions.py
  - scheduled_tasks.py
  - settings.py
- tests
Includes test framework (py.test)
Includes database migration framework (alembic)
Sends error emails to admins for unhandled exceptions

Setting up a development environment

We assume that you have git and virtualenv and virtualenvwrapper installed. For Windows, install pipenv.

# Clone the code repository into ~/dev/my_app
mkdir -p ~/dev
cd ~/dev
git clone https://github.com/NHanser/flask-celery-sqlalchemy.git my_app

# Create the 'my_app' virtual environment using virtualenv
cd ~/dev/my_app
py -3 -m venv venv # Windows command
OR  
mkvirtualenv -p PATH/TO/PYTHON my_app # Linux/MacOs command

# Install required Python packages
.\venv\Scripts\Activate.ps1 # Windows powershell
OR
workon my_app # Linux or MacOS

#Then
pipenv install

Configuring SMTP

Copy the .env_template file to .env.

cp .env_template .env

Edit the .env file.

Specifically set all the MAIL_... settings to match your SMTP settings

Note that Google's SMTP server requires the configuration of "less secure apps". See https://support.google.com/accounts/answer/6010255?hl=en

Note that Yahoo's SMTP server requires the configuration of "Allow apps that use less secure sign in". See https://help.yahoo.com/kb/SLN27791.html

Initializing the Database

Create local postgresql database

mkdir -p ~/dev/my_app/postgresql-data

Create DB tables and populate the roles and users tables

flask db init
flask db migrate -m "Initial version"
flask db upgrade

Fill the database with 2 sample users

flask init create-users

create feeds (optional)

flask init create-feeds

Debug the app

Set environment

Copy template file

cp dev/docker.env.template dev/docker.env

Then edit dev/docker.env

Docker compose

docker compose -f "dev/docker-compose.yml" up -d --build

Launch debug configuration in VSCode

If you don't launch debugger, application will not start

{
    "name": "Python: Remote Attach",
    "type": "python",
    "request": "attach",
    "port": 5678,
    "host": "localhost",
    "pathMappings": [
        {
        "localRoot": "${workspaceFolder}",
        "remoteRoot": "/myapp"
        }
    ]
},

Point your web browser to http://localhost:5000/

You can make use of the following users:

email user@example.com with password Password1.
email admin@example.com with password Password1.

Running the automated tests

# Run pytest
python -m pytest --setup-show --cov=app

Trouble shooting

If you make changes in the Models and run into DB schema issues, delete the sqlite DB file app.sqlite.

Acknowledgements

With thanks to the following Flask extensions:

Flask-User-starter-app was used as a starting point for this code repository.

Authors

Nicolas Hans (NHanser)