Compose Env

Compile docker-compose files for different environments using an ERB template.

The proposed approach might differ from the canonical way of handling multiple docker-compose environments and extending the services for specific cases. So it might worth it to check the official documentation describing how to extend services and also how to add and override configuration.

Anyway I find it sometimes easier to have the Puppet-like ERB template which describes all the services in one place when building a small MVP application without a lot of dependencies.

Usually I used a couple of Makefile instructions before, but it is just much simpler to have these several steps defined in one gem and be available as one executable command from the console. You can use boths: compose_env or compose-env that's up to you, both commands are equal.

gem install 'compose_env'

And then execute:

$ compose-env --help

Or:

$ compose_env --help

Create a docker-compose.yml.erb file with the following content inside of your project directory:

version: "3.9"
services:
  db:
    image: postgres
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
    environment:
      POSTGRES_PASSWORD: <%= !development? ? 'strong123password' : 'password' %>
  web:
    <% if env.production? %>
    image: my_app:v0.1
    <% else %>
    build: .
    <% end %>
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/myapp
    environment:
      RAILS_ENV: <%= current_env %>
    ports:
      <% development do %>
      - "3000:3000"
      <% end %>
      - "80:3000"
    depends_on:
      - db

Now execute the command:

compose-env -f docker-compose.yml.erb  -e production, development

The result will be the following:

docker-compose.development.yml

---
version: '3.9'
services:
  db:
    image: postgres
    volumes:
    - "./tmp/db:/var/lib/postgresql/data"
    environment:
      POSTGRES_PASSWORD: password
  web:
    build: "."
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b
      '0.0.0.0'"
    volumes:
    - ".:/myapp"
    environment:
      RAILS_ENV: development
    ports:
    - 3000:3000
    - 80:3000
    depends_on:
    - db

docker-compose.production.yml

---
version: '3.9'
services:
  db:
    image: postgres
    volumes:
    - "./tmp/db:/var/lib/postgresql/data"
    environment:
      POSTGRES_PASSWORD: strong123password
  web:
    image: my_app:v0.1
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b
      '0.0.0.0'"
    volumes:
    - ".:/myapp"
    environment:
      RAILS_ENV: production
    ports:
    - 80:3000
    depends_on:
    - db

As you can see the command provides you a couple of helper methods to pick out the proper configuration for each environment based on the environments passed to the --envs (or -e) option:

environment? returns a boolean value for the particular environment and can be used with if/else operators.

Which can be also used as a block of code. The code will be executed only if current environment statisfies the check.

<% environment do %>
  # environment specific code here...
<% end %>

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the ComposeEnv project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.