RAILS_ROOT and USR2 restarts

Ian Leitch port001 at gmail.com
Mon Oct 26 11:04:56 EDT 2009


I've just started using Unicorn in production behind Nginx with a
Rails app, for the most part its been a smooth transition apart from
this one issue.
When I do an in place restart (USR2), the restart process works but
the workers load my old Rails release, not the new one. I'm guessing
that because the master process is currently in the old release
directory, when I signal USR2 it's just reloading inside the current
directory. I'm deploying with Capistrano, so app/current is a symlink
to a specific release. I've tried changing to the new release
directory in before_work but that made no difference. Is there a
callback that fires before the master preloads the app?

worker_processes 6
preload_app true
timeout 60
listen "/tmp/unicorn.production.sock"
pid "/tmp/unicorn.production.pid"

before_fork do |server, worker|
  old_pid = "/tmp/unicorn.#{RAILS_ENV}.pid.oldbin"
  if File.exists?(old_pid) && server.pid != old_pid
      Process.kill("QUIT", File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
      # someone else did our job for us

after_fork do |server, worker|

I also have a little launcher script (I'm using Solaris - SMF doesn't
let me provide a custom restart routine, so I have to bypass it and
use this script):

$rails_env = ARGV[0]
$pid_file = "/tmp/unicorn.#{$rails_env}.pid"
def restart(pid)
  system("kill -USR2 #{pid}")
def start
  system("/opt/local/bin/unicorn_rails -c config/unicorn.rb -E
#{$rails_env} -D")
if File.exists?($pid_file)
  pid = File.read($pid_file).strip.to_i
    Process.kill(0, pid)
  rescue Errno::ESRCH
    # Not running

At the end of the deploy I execute:

task :restart_unicorn do
  run "cd #{current_path}; ruby config/unicorn_launcher.rb #{rails_env}"

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