RailsCommander is a library that allows the programmatical control over a Rails process. It's a Ruby wrapper for Rails' CLI interface.

Typical use case can be a CI job definition that, among many other steps, requires a spin-up of a Rails app, that is a part of a bigger system under test.

config = RailsCommander::Config.new(
  port: 3004                  # default: 3000
  pidfile: '/tmp/server.pid'  # default: ./tmp/pids/server.pid
  out_path: '/tmp/stdout.log' # default: a new tmp file
  err_path: '/tmp/stderr.log' # default: a new tmp file
  env_vars: { 'DEBUG': 1 }    # default: {}
  rails_env: 'cucumber'       # default: development
  unset_env_vars: false       # default: true
)

# config is a Struct, so this will work too:
config.port = 3005

app = RailsCommander::App.new('/path/to/rails/application', config)
app.task('db:reset') # bundle exec rails db:reset
app.start            # bundle exec rails server with given port, env, etc
app.stop             # kill the rails process created with start method
app.stdout           # get the stdout content
app.stderr           # get the stderr content
app.running?         # check if process is running

# or just use default config to run take tasks, without starting the server
RailsCommander::App.new('/path/to/rails/application').task('db:migrate')

Possible caveats

Even though the commands are executed in the another process, in Rails' apps directory, the bundler context may be inherited from the parent process through the environment variables, causing errors about missing gems.

If this happens unset BUNDLE_GEMFILE env variable in the config object before starting the app.

RailsCommander::Config.new(env_vars: { 'BUNDLE_GEMFILE' => nil })

Testing

Before running rspec:

• before first execution: install dependencies required by the embedded test rails app:

cd spec/support/bookstore
bundle install
cd -

• start the mysql instance for the embedded test rails app:

docker run --rm --name bookstore-mysql -e MYSQL_ROOT_PASSWORD=root -e MYSQL_DATABASE=bookstore -e MYSQL_USER=bookstore -e MYSQL_PASSWORD=bookstore -p 3309:3306 mysql/mysql-server:5.6

To test your changes:

bundle exec rubocop
bundle exec rspec