Docker for Ruby

Based on https://github.com/docker/awesome-compose/tree/master/official-documentation-samples/rails/ conception.

Useful for creating new, empty application.

Step 1

Clone this repository or copy to your project these files:

• .env
• docker-compose.yaml
• Dockerfile
• entrypoint.sh
• Gemfile
• Gemfile.lock

All files from root directory, besides images/, .gitattributes and README.md.

Step 2

Create new Rails application:

$ docker compose run --rm --build --no-deps web rails new . --force --database=postgresql

Step 3

Gemfile has different content after new Rails application has been created, so you have to build Docker image once again:

$ docker compose build

Step 4

Configure database connection:

1. Open config/database.yml file

2. Find default: &default section:

   default: &default
     adapter: postgresql
     encoding: unicode
     # For details on connection pooling, see Rails configuration guide
     # https://guides.rubyonrails.org/configuring.html#database-pooling
     pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

3. Append these options at the end:

   host: db
   username: app
   password: p4ssw0rd

   So the default: &default section may look like this:

   default: &default
     adapter: postgresql
     encoding: unicode
     # For details on connection pooling, see Rails configuration guide
     # https://guides.rubyonrails.org/configuring.html#database-pooling
     pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
     host: db
     username: app
     password: p4ssw0rd

Step 5

Let's start all containers:

$ docker compose up -d

Step 6

Create all databases:

$ docker compose exec web rake db:create

Step 7

Open application by entering http://localhost:3000 in web browser:

Enjoy!