Summary

Hi I'm Kei, front-end developer. This Quickstart guide shows you how to use Docker Compose to set up and run a Rails6/PostgreSQL app.

Define the project

First, make files as follows.

├── .env
├── Dockerfile
├── Gemfile
├── Gemfile.lock
├── docker-compose.yml

1.Update Gemfile and .env

Don't private your ".env" file.

# Gemfile
source 'https://rubygems.org'
gem 'rails', '~> 6.0.0'

#.env
WORKDIR=app
API_PORT=3000
POSTGRES_PASSWORD=password

2.Update Docker file

FROM ruby:3.0.3-alpine

ARG WORKDIR
ARG RUNTIME_PACKAGES="nodejs tzdata postgresql-dev postgresql git" 
ARG DEV_PACKAGES="build-base curl-dev"

ENV HOME=/${WORKDIR} \
    LANG=C.UTF-8 \
    TZ=Asia/Tokyo

WORKDIR ${HOME}

COPY Gemfile* ./

RUN apk update && \
    apk upgrade && \
    apk add --no-cache ${RUNTIME_PACKAGES} && \
    apk add --virtual build-dependencies --no-cache ${DEV_PACKAGES} && \
    bundle install -j4 && \
    apk del build-dependencies

COPY . ./

CMD ["rails", "server", "-b", "0.0.0.0"]

3.Update docker-compose.yml

version: '3.8'

services:
  db:
    image: postgres:12.3-alpine
    environment:
      TZ: UTC
      PGTZ: UTC
      POSTGRES_PASSWORD: $POSTGRES_PASSWORD
    volumes:
      - ./tmp/db:/var/lib/postgresql/data

  api:
    build:
      context: ./
      args:
        WORKDIR: $WORKDIR
    environment:
      POSTGRES_PASSWORD: $POSTGRES_PASSWORD
    volumes:
      - ./:/$WORKDIR
    depends_on:
      - db
    ports:
      - "$API_PORT:3000"

Build the project

docker-compose build

You can generate automatically the Rails template.

docker-compose run --rm api rails new . -f -B -d postgresql --api

Explanation of "rails new" options here.

＜run [Container Name] [Command]＞
You can create container and execute command like "rails c..." and so on.

< -B >
Don't run bundle install.

< -d >
Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc)

< --api >
Create Rails template with API mode.

Setting the database

Update database.yml that are generated "rails new" command.

default: &default
  adapter: postgresql
  encoding: unicode
  host: db
  username: postgres
  password: <%= ENV["POSTGRES_PASSWORD"] %>
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

# create db
docker-compose run --rm api rails db:create

# run container
docker-compose up api or docker-compose up api -d

Access localhost:3000.