Rails commands multi-process demo

superconsole.rb

#!/usr/bin/env ruby

# Rails commands multi-process demo
#
# For use with https://github.com/rails/commands
#
# Put this file in an app in script/superconsole (or whatever name) and chmod +x
# or just put this in lib/superconsole.rb.
#
# This script opens the console in the development env, and forks a child process
# with the app in the test env.
#
# Console can send commands to the test env via the "testenv" method, e.g.:
#
#    testenv.rake 'about'
#
# This message is sent to the testenv via a Unix socket

require 'socket'

# create unix socket to enable message passing between parent process (dev env) and child (test env)
CHILD_SOCKET, PARENT_SOCKET = Socket.pair(:UNIX, :DGRAM, 0)

APP_PATH = File.expand_path('../../config/application',  __FILE__)
require File.expand_path('../../config/boot',  __FILE__)

# load gems before forking
Bundler.require(:default, :assets)

# fork for test environment
child_pid = fork do
  ENV['RAILS_ENV'] = Rails.env = 'test'
  require APP_PATH
  Rails.application.require_environment!

  trap(:INT) { exit(0) } # close silently

  commander = Rails::Commands::Commander.new

  loop do
    msg = CHILD_SOCKET.recv(1000)
    # puts "[#{Rails.env}] received message: #{msg.inspect}\n"

    argv = msg.split(' ')
    command = argv.shift
    args = argv.join(' ')
    args = nil unless args.match(/\S/)
    retval = if commander.respond_to?(command)
      commander.send(command, args)
    else
      'Unrecognized command'
    end

    CHILD_SOCKET.write(retval)
  end
end

# cleanup: kill child process at exit
at_exit do
  Process.kill(:INT, child_pid)
end

# enable communication between dev console and test env child process
module TestEnv
  def self.send msg
    PARENT_SOCKET.write(msg)
    PARENT_SOCKET.recv(1000)
  end

  def self.method_missing(m, *args, &block)
    send "#{m} #{args.join(' ')}"
  end
end

module ConsoleDelegationOverride
  def testenv
    TestEnv
  end

  def test *args
    testenv.test *args
  end
end

require 'rails/commands/console'
require APP_PATH
Rails.application.require_environment!
Rails::ConsoleMethods.send :include, ConsoleDelegationOverride
Rails::Console.start(Rails.application)

Should be easy enough to have the bare "test" command delegate to testenv.test in the parent process, and actually run the tests in the child.

Added ConsoleDelegationOverride, so that the bare test command now runs in child process

I made this a gem: https://github.com/gbuesing/duoconsole