A quickstart to dockerizing your existing Rails-Postgresql application with Docker compose
Dockerfiles — Define the project
Create Dockerfile in the app’s root directory, the project is defined by adding the dependencies to the Dockerfile.
FROM ruby:2.5.3
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
RUN mkdir /myapp
WORKDIR /myapp
COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
COPY . /myapp
Make sure add the specific version of ruby that your application uses
Docker-compose — Build the project
Now, create docker-compose.yml file in the root directory. This file does the magic of building your app from the current directory and running the pre-built postgresql image with the web app
version: '3'services:db:image: postgresvolumes:
-
./tmp/db:/var/lib/postgresql/dataweb:build: .command: bundle exec rails s -p 3000 -b '0.0.0.0'volumes:
-
.:/myappports:
-
"3000:3000"depends_on:
- db
Database.yml — Configure DB
Now, Change the host to ‘db’ in your database.yml file to point to the docker service
default: &default
adapter: postgresql
encoding: unicode
host: db
username: postgres
password:
pool: 5
development:
<<: *defaultdatabase: myapp_development
The following tasks can be completed be completed by running the respective commands
Build Docker Image
docker-compose build
DB — Create and Migrate
docker-compose run web rake db:create db:migrate
Accessing Rails Console
docker-compose exec web rails console
Start application
docker-compose up
You should now be able to browse to http://localhost:3000 and see your application running.