unicorn + rake voltron

railsapp-lib-tasks-unicorn.rb

require 'net/http'

namespace :server do
  ROOT = ENV['HOME'] || File.expand_path('../../../', __FILE__)
  PIDFILE = File.join(ROOT, 'shared/pids/server.pid')

  def get_pid
    # XXX: this should be more intelligent, and check if,
    #      a) the pid is still alive,
    #      b) pid is actually unicorn
    raise 'Server is not running' unless File.exists? PIDFILE
    File.read(PIDFILE).to_i
  end

  def send_signal(pid, signal = :INT)
    Process.kill signal, pid
  end

  def do_start
    system "cd #{ROOT}/current >/dev/null 2>&1 ; bundle exec unicorn_rails -c #{ROOT}/current/config/unicorn.rb -D"
  end

  def do_restart
    pid = {}

    pid[:old] = get_pid rescue nil
    if pid[:old]
      # hey! i want a new process
      send_signal pid[:old], :USR2

      # wait for unicorn to spawn new process
      sleep 5

      # get new pid, and compare with old
      pid[:new] = get_pid
      raise "Could not start new Unicorn master process" if pid[:old] == pid[:new]

      # tell old process to stop handling new requests
      send_signal pid[:old], :WINCH

      # hit a healthcheck url in app, to make sure we're functioning
      # XXX: port should be configurable
      # XXX: url should be configurable, and NOT static
      uri = URI.parse 'http://localhost:18241/favicon.ico'
      resp = Net::HTTP.get_response uri rescue nil

      # if url fetch failed, then go back to old process
      unless resp and resp.code == '200'
        send_signal pid[:old], :HUP
        send_signal pid[:new], :QUIT
        raise 'Started new Unicorn process, but it is not serving requests as expected, reverting...'
      end

      # kill the old process, notify user
      send_signal pid[:old], :QUIT
      puts "replaced app, pid #{pid[:old]} with #{pid[:new]}"
    else
      do_start
    end
  end

  task :start do
    do_start
  end

  task :stop do
    send_signal get_pid
  end

  task :restart do
    do_restart
  end
end

desc 'Start the web application'
task :start => [ 'server:start' ]

desc 'Stop the web application'
task :stop => [ 'server:stop' ]

desc 'Restart the web application'
task :restart => [ 'server:restart' ]
task :default do
  puts
  puts 'rake <action>'
  puts '* valid actions: start, stop, restart'
  puts
end