config/unicorn.rb

unicorn.rb

rails_root = File.expand_path('../../', __FILE__)
listen "#{rails_root}/tmp/sockets/unicorn.sock"
pid "#{rails_root}/tmp/pids/unicorn.pid"

stdout_path "#{rails_root}/log/#{:stage}.log"
stderr_path "#{rails_root}/log/#{:stage}.log"

timeout 60
worker_processes Integer(ENV["WEB_CONCURRENCY"] || 2)

#no downtime
preload_app true

GC.respond_to?(:copy_on_write_friendly=) and GC.copy_on_write_friendly = true

before_fork do |server, worker|
  defined?(ActiveRecord::Base) and ActiveRecord::Base.connection.disconnect!
  old_pid = "#{server.config[:pid]}.oldbin"
  if old_pid != server.pid
    begin
      sig = (worker.nr + 1) >= server.worker_processes ? :QUIT : :TTOU
      Process.kill(sig, File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
    end
  end
  sleep 1
end

after_fork do |server, worker|
  defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection
end