Docker done right

For development purposes only. The idea is that you enter a docker container and you can run your application as usual on your host machine but it has all system dependecies installed.

Index

1. Why is it right?
2. Dockerfile
3. docker-compose.yml
4. Final result

Why is it right?

This approach does not force developers to use docker. It is as easy as always to setup the project natively on host machine (a developer's laptop).

Dockerfile

First I created Dockerfile with the next content:

FROM ruby:3.1.0-alpine

ARG RAILS_ROOT=/docker-done-right
ARG PACKAGES="vim openssl-dev postgresql-dev mongodb-tools build-base \
  curl less tzdata git postgresql-client bash"

RUN apk update \
  && apk upgrade \
  && apk add --update --no-cache $PACKAGES

And run

docker build -t ddr .
docker run -it --rm -v $PWD:/docker-done-right ddr bash
gem install rails

rails new docker-done-right \
  --database=postgresql --skip-active-storage \
  --skip-action-cable --skip-test --skip-system-test --api

exit

After the project generated in the container it appeared on my host machine.

First try to run the server

docker run -it --rm -v $PWD:/docker-done-right -p 3000:3000 ddr bash
rails server -b 0.0.0.0

And we can open localhost:3000 in our browser and see an error! It works!

docker-compose.yml

My application grew and got ActiveRecord models and Mongoid documents and now it relies on PostgreSQL and MongoDB databases. So to run my app I need to run them first.

version: '3.7'

services:
  web:
    build: .
    volumes:
      # mount application directory so that changes I make on my local machine
      # with graphical code editor appear in application container and
      # generated code (produced with rails generate) appear on my local machine
      # and shown in code editor
      - .:/docker-done-right:cached
      # save the bundle between container runs
      - bundle_cache:/bundle_cache
    ports:
      - 3000:3000
    depends_on:
      # in fact it does not depend on mongo and postgres until I start
      # my application with rails server command
      - postgres
      - mongo
    environment:
      # tell bundler where to store gems
      BUNDLE_PATH: /bundle_cache
      # tell gem command where to store gems
      GEM_HOME: /bundle_cache
      GEM_PATH: /bundle_cache

      RAILS_PORT: 3000

      # environment variables for the app
      DATABASE_HOST: postgres
      DATABASE_USERNAME: postgres
      DATABASE_PASSWORD: postgres
      MONGODB_HOST: mongo
    # make web container hang so that I connect to it
    stdin_open: true
    tty: true
    command: bash

  postgres:
    image: postgres:14.1-alpine
    volumes:
      - pg_data:/var/lib/postgresql/data/pgdata
    ports:
      - 5432:5432
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      PGDATA: /var/lib/postgresql/data/pgdata

  mongo:
    image: mongo
    volumes:
      - mongo_data:/data/db
    ports:
      - 27017:27017
    restart: always

volumes:
  bundle_cache:
  mongo_data:
  pg_data:

Final result

From now on to setup the project from scratch there is only a few commands:

1. Clone the projects itself:
   git clone git@github.com:DmitryBarskov/docker-done-right.git && cd docker-done-right
2. Setup the development environment, run tests and enter the development environment:
   bin/docker
3. Run the server as usual (binding on 0.0.0.0 is required):
   bin/server

So there are only a few commands to get started.
But at the same time I can setup my project as I always do installing Ruby, PostgreSQL, etc on my host machine.