Мой конфиг Unicorn (скопировано сHeroku»документы):

# config/unicorn.rb
worker_processes Integer(ENV["WEB_CONCURRENCY"] || 3)
timeout 30
preload_app true

before_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
    Process.kill 'QUIT', Process.pid
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.connection.disconnect!
end 

after_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.establish_connection
end

Но каждый раз, когда dyno перезапускается, мы получаем это:

heroku web.5 - - Error R12 (Exit timeout) -> At least one process failed to exit within 10 seconds of SIGTERM

Ruby 2.0, Rails 3.2, Unicorn 4.6.3