martlark/flask-gunicorn-3-11 repository overview

⁠flask-gunicorn-3-11

Python 3.11 Flask server using Gunicorn container.

Includes:

• Support for sqlalchemy
• Migration of database
• Gunicorn options
• Database pre and post start scripts
• Scripts to run before starting server

Upgrades to latest Pip, starts the DB, performs any migrations to the database structure, then loads and runs Flask app using Gunicorn.

Assumes code starts from main.py using app as the application variable.

NOTE: Flask and other package dependencies should be defined in your application's requirements.txt file. This image does not include Flask or SQLAlchemy by default.

⁠Example main.py

# start app for flask-gunicorn-3-11
# from /app

import os

from app.app import create_app


app_path = "/app"
if os.path.isdir(app_path):
    sys.path.insert(0, app_path)
    os.chdir(app_path)

app = create_app()

⁠Example Dockerfile

FROM martlark/flask-gunicorn-3-11:latest

# copy over our requirements.txt file
COPY requirements.txt /tmp/
# install required python packages
RUN pip install -r /tmp/requirements.txt

# copy over our app code
COPY . /app

⁠Examples

Example Dockerfile and Python source can be found in the martlark directory.

⁠Options

Environment variables can be used to change the container startup process.

Container will check for scripts in the /persist/ folder which can be mapped into the container using the volume directive.

Docker compose volumes example:

version: '3.7'

services:
  app:
    build: martlark
    ports:
      - "18008:80"
    volumes:
      - ./persist:/persist
    environment:
      GUNICORN_THREADS: 4
    restart: unless-stopped

⁠Script to run before start

/persist/before.sh

⁠Use SQLALCHEMY

Set environment variable SQLALCHEMY_DATABASE_URI to enable SQLAlchemy database use.

⁠Script to run before starting db and migration

/persist/before_db.sh

⁠Options for waiting for db to start

When SQLALCHEMY_DATABASE_URI environment variable is set the container will wait for the database to start then run any migrations.

⁠Retry attempts

Container will wait for the database to be ready and retry this many times.

DB_READY_RETRIES=20

⁠Seconds to wait between db ready retries

DB_READY_SLEEP_SECONDS=2

⁠Flask application file

This environment variable defines the app to be used for flask commands. By default, this is main.py.

FLASK_APP=main.py

⁠Migration command

Migration will be done using flask-migrate. Reference: https://flask-migrate.readthedocs.io/en/latest/⁠

For Alembic refer to their documentation. Reference: https://alembic.sqlalchemy.org/en/latest/index.html⁠

If you do not want any migrations then set FLASK_DB_UPGRADE to true.

Override the migration command when not using flask-migrate.

FLASK_DB_UPGRADE="flask db upgrade"

⁠Script to run after starting db and migration

Run a script after the database is up and migration is completed.

/persist/after_db.sh

⁠Gunicorn configuration

Options to control how Gunicorn is started.

⁠Flask python app module and app variable

Use this environment variable to change the default value of main:app.

GUNICORN_MAIN="main:app"

⁠Number of threads

Use this environment variable to change the default value of 2.

GUNICORN_THREADS="2"

⁠Server Port

Exposed port is always 80