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Docker Compose setup for Ruby & Ruby on Rails apps
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README.md

Ruby on Whales

Inspired by Dockerizing Ruby and Rails development blog post.

It's a Docker Compose template repository that should helps in bootstrapping an environment for writing new Ruby and/or Ruby on Rails applications.

Also, it is possible to comment out (or delete) unnecessary services that you do not need to have in simple Ruby projects (for example, sidekiq, or redis, or everything except the app container).

Below we provided a step-by-step instructions on how to bootstrap your local development environment.

Tips&Tricks

docker-compose up

The main command we will be using is , which attempts to init all the services described in the configuration file. If it's just the first time user runs the command, it will download and install all the prerequisites, build the app image, and set environment up and running.

docker-compose exec shell bash

Runs a bash session in the app environment (so you can use ruby, irb, bundle, rails, rake, and many other commands.

New Ruby on Rails Application

Here is the way of we can use this approach to create a fresh new Ruby on Rails application. We consider that you just cloned this repository and have nothing else in the current directory.

$ git clone git@github.com:cr0t/ruby-on-whales.git <your-app-name>

$ cd <your-app-name> && rm -rf .git

$ mv .env.example .env

$ mv README.md README-ON-WHALES.md # we need this to avoid conflicts with app's README.md

# now you can open docker-compose.yml, remove services you do not need
# and adjust versions and other settings in the .env file before you proceed

$ docker-compose up

This step takes some time to download and build images. If it went well you should see a lot of output and eventually notifications about running services (depends on which you left in the configuration file).

In a separate terminal you need to start a new shell session to install Ruby on Rails gem and other libraries you want.

$ docker-compose exec shell bash

# this gives us a bash session inside our Docker containers, so we can run our favourite ruby/rails commands, for example:

root@11f8d8b944bb:/app# gem install rails
root@11f8d8b944bb:/app# rails new . --database=postgresql

...are we there yet?!

Almost. Let's install Sidekiq and configure our new lovely Ruby on Rails app to use the shiny Docker environment.

We need to install sidekiq and configure it, also, we need to update database.yml, so our Ruby on Rails app can use it:

root@11f8d8b944bb:/app# vim Gemfile # yes, we can edit Gemfile inside container, but you can do it on the host machine too
root@11f8d8b944bb:/app# bundle install
root@11f8d8b944bb:/app# vim config/initializers/sidekiq.rb
root@11f8d8b944bb:/app# cat config/initializers/sidekiq.rb
Sidekiq.configure_server do |config|
  config.redis = { url: 'redis://redis:6379/0'  }
end

Sidekiq.configure_client do |config|
  config.redis = { url: 'redis://redis:6379/0'  }
end
root@11f8d8b944bb:/app# vim config/sidekiq.yml
root@11f8d8b944bb:/app# cat config/sidekiq.yml
---
:concurrency: 5
staging:
  :concurrency: 10
production:
  :concurrency: 20
:queues:
  - critical
  - default
  - low
root@11f8d8b944bb:/app# vim config/database.yml
root@11f8d8b944bb:/app# cat config/database.yml
# ...
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 } %>
  url: <%= ENV.fetch("DATABASE_URL") %>
# ...
root@11f8d8b944bb:/app# rake db:create
root@11f8d8b944bb:/app# exit
$ docker-compose stop # or down
$ docker-compose start # or up

We need to run two last commands to re-start all services defined in docker-compose.yml (if we left it original).

Ok! Now you can try to open http://localhost:3000/ in the browser on the host machine and check if you see Ruby on Rails welcome page.

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