Docker & Docker Compose on Raspberry Pi

Docker isolates our applications so it’s much more reusable across any machine that runs docker. Docker Compose helps us manage several containers at once in coordination with each other. Learn more about Docker & Docker Compose in this tutorial series.

1. Update, Upgrade, & Clear Out the Old

sudo apt update && sudo apt upgrade

Do you have supervisor running your apps like we did in this one? If so, remove supervisor as docker will manage itself

sudo apt-get purge supervisor # removes everying including config files

Do you have nginx running like we did in this one? If so, remove it as we’ll use Docker to run nginx:

sudo apt-get purge nginx nginx-common # removes everying including config files

Do you want to remove all of docker and start fresh?

sudo apt remove docker-ce*

Remove stale packages:

sudo apt-get autoremove

2. Install Docker

curl -sSL https://get.docker.com | sh

This installs docker-engine.

Verify docker is installed with:

sudo systemctl status docker

and

sudo docker ps

If we run docker ps we’ll see a permissions error. Let’s add our user to the docker group.

3. Add user to docker group

sudo usermod -a -G docker $(whoami)

Reboot or logout/login to finalize group changes

4. Install Docker Compose

At this time, docker-compose must be installed via your global python3 installation after docker is installed above.

which python3

Does this return nothing? That means python3 is not installed. Run sudo apt install python3-pip python3

sudo python3 -m pip install docker-compose

In newer versions of Docker Destkop, Docker Compose is included in the docker installation which means you’ll use docker compose instead of docker-compose like we do below.

5. Minimal Gunicorn-based Flask App

For this example, I’ll be using the directory /var/www/flaskapp to store all of the files created.

server.py

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello_world():
    return "Hello world!"

wsgi.py

from server import app


if __name__=="__main__":
    app.run()

requirements.txt

flask
gunicorn

run.sh

#!/bin/bash

RUN_PORT=${PORT:-8010}
/app/bin/gunicorn --pid /app/bin/flaskapp.pid --bind 0.0.0.0:$RUN_PORT  wsgi:app

6. Minimal Dockerfile for Flask/Django/FastAPI

Dockerfile

FROM python:3.7-slim

COPY . /app
WORKDIR /app


RUN python3 -m venv .
RUN /app/bin/pip install pip --upgrade
RUN /app/bin/pip install -r requirements.txt

RUN chmod +x run.sh

CMD ["./run.sh"]

Also add: .dockerignore

bin/
include/
lib/
share/
__py_cache__/

7. Minimal Nginx Configuration

upstream flaskappproxy {
    server flaskapp:8081;
}

server {
    listen       80;
    server_name  localhost;
    root   /www/html/;


    location / {
        proxy_pass http://flaskappproxy;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
    }

    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/share/nginx/html;
    }
}

Be sure to note that flaskapp is the service name while flaskappproxy is merely the proxy name within nginx. The flaskapp service name will be used below in docker-compose.yaml. The port of 8081 will be reused below as well.

8. Dockerfile for nginx

Dockerfile.nginx

FROM nginx:latest

COPY ./nginx.conf /etc/nginx/conf.d/default.conf

9. Minimal docker-compose.yaml

version: '3.2'
services:
    flaskapp:
        restart: 'always'
        build:
            context: .
            dockerfile: Dockerfile
        environment: 
            - PORT=8081
        expose: 
            - 8081
    nginx:
        restart: 'always'
        build:
            context: .
            dockerfile: Dockerfile.nginx
        ports:
            - 80:80
        volumes: 
            - ./nginx.conf:/etc/nginx/nginx.conf
        depends_on: 
            - flaskapp

10. Run Docker Compose

sudo docker-compose up -d --build

Ensure this is in the root of your app or use the flag -f path/to/your/docker-compose.yaml

Let’s break this down:

• sudo In order to allow the ports for nginx to exposed properly, we use the superuser
• docker-compose up this is how we bring up our docker compose network
• -d This puts docker-compose in detatched mode; which allows it to run in the background
• --build means docker-compose will build the necessary container images

11. Stop Docker Compose

Above we use -d to run docker-compose in detached mode. Now we can stop it with:

docker-compose down -f path/to/your/docker-compose.yaml

12. Update single service

docker-compose stop flaskapp
docker-compose rm -f  flaskapp
docker-compose up --build -d flaskapp 

This will allow nginx to continue running while the flaskapp service is rebuilt