Apache2 Flask Container

What is this repo?

A template for hosting Flask apps with Apache2 acting as the HTTP server.

Outline

The Dockerfile works by copying Flask app project files directly into the container and installing dependencies at build time.

Build Arguments

The Dockerfile needs to know where core app files are located so they can be copied onto the container. Project files are specific via build arguments. The following must be specified at build time.

Argument	Description
APP_ROOT_DIR	Project root directory
FLASK_ROOT_FILE	Root Flask app Python file
WSGI_FILE	WSGI file that references FLASK_ROOT_FILE
APACHE_CONF	Apache2 `.conf` file

For example if our Flask app had the following layout:

.
├── Dockerfile
├── apache2_files
│   └── app.conf
│   └── app.wsgi
├── example_app
│   ├── __init__.py
│   └── ...
├── flask_app.py

We'd want our build args set up like so:

Argument	File Path
APP_ROOT_DIR	./example_app
FLASK_ROOT_FILE	./flask_app.py
WSGI_FILE	./apache2_files/app.wsgi
APACHE_CONF	./apache2_files/app.conf

Build The Docker Image

Using the example project layout given above we'd build our container as follows

docker build -dt \
  --build-arg APP_ROOT_DIR="./example_app" \
  --build-arg FLASK_ROOT_FILE="./flask_app.py" \
  --build-arg WSGI_FILE="./apache2_files/app.wsgi" \
  --build-arg APACHE_CONF="./apache2_files/app.conf" \
  --name flask-app \
  .

Run The Docker Image

The only thing that really needs to be handled when running the resulting container is port mapping. Port 80 is exposed by default and if there's a desire to map this to an alternate port on the host that needs to be handled with the -p run flag.

docker run -dt \
  -p 5000:80 \
  --name flask-app \
  --restart=always \
  flask-app

Example Docker-Compose File

Again assuming our project is laid out as in our example we could tie everything together using a Docker-Compose file.

version: '2.2'
services:

  flask:
    restart: always
    image: flask_app:latest
    build:
      context: ./
      args:
        APP_ROOT_DIR: ./
        FLASK_ROOT_FILE: ./flask_app.py
        WSGI_FILE: ./apache2_files/app.wsgi
        APACHE_CONF: ./apache2_files/app.conf
    networks:
      - external_network
    healthcheck:
        test: curl --fail http://localhost:5000/ping || exit 1
        interval: 10s
        timeout: 2s
        retries: 5
    ports:
      - 5000:80

networks:
  external_network:
    driver: bridge
    ipam:
      driver: default

Limitations

Only plain HTTP communication with the resulting app is supported "out of the box" at the moment.

Manually adding SSL Encryption

Here's an example of the steps required to manually set up SSL certificates through Let's Encrypt after a container is already provisioned and running.

# Base Ubuntu Docker image cannot add PPA's by default
# We need to install software-properties-common in order to enable this functionality
apt-get install software-properties-common

add-apt-repository ppa:certbot/certbot
apt-get update
apt-get install python-certbot-apache

certbot --apache -d $SITE_URL
# Select `app.conf` when prompted

a2enmod rewrite

# Set up cron job to handle automatic renewal of certificates.
(crontab -l 2>/dev/null; echo "15 3 * * * /usr/bin/certbot renew --quiet") | crontab -

SashaNullptr / Apache-Flask-Container