rails + unicorn + rbenv + init.d daemon

Gemfile

group :production do
  gem "unicorn"
end

unicorn.rb

APP_DIR = File.expand_path("../../", __FILE__)

# This loads the application in the master process before forking
# worker processes
# Read more about it here:
# http://unicorn.bogomips.org/Unicorn/Configurator.html
preload_app true
worker_processes 4
working_directory APP_DIR

# This is where we specify the socket.
# We will point the upstream Nginx module to this socket later on
listen "#{APP_DIR}/tmp/sockets/unicorn.sock", :backlog => 64

# nuke workers after 30 seconds instead of 60 seconds (the default)
timeout 30

# feel free to point this anywhere accessible on the filesystem
# user 'nginx', 'www-data'

pid "#{APP_DIR}/tmp/pids/unicorn.pid"
stderr_path "#{APP_DIR}/log/unicorn.stderr.log"
stdout_path "#{APP_DIR}/log/unicorn.stdout.log"

# http://www.rubyenterpriseedition.com/faq.html#adapt_apps_for_cow
if GC.respond_to?(:copy_on_write_friendly=)
  GC.copy_on_write_friendly = true
end

before_fork do |server, worker|
  # the following is highly recomended for Rails + "preload_app true"
  # as there's no need for the master process to hold a connection
  defined?(ActiveRecord::Base) and ActiveRecord::Base.connection.disconnect!

  ##
  # When sent a USR2, Unicorn will suffix its pidfile with .oldbin and
  # immediately start loading up a new version of itself (loaded with a new
  # version of our app). When this new Unicorn is completely loaded
  # it will begin spawning workers. The first worker spawned will check to
  # see if an .oldbin pidfile exists. If so, this means we've just booted up
  # a new Unicorn and need to tell the old one that it can now die. To do so
  # we send it a QUIT.
  #
  # Using this method we get 0 downtime deploys.

  old_pid = "#{server.config[:pid]}.oldbin"

  if File.exists?(old_pid) && server.pid != old_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
      # someone else did our job for us
    end
  end
end

after_fork do |server, worker|
  # Unicorn master loads the app then forks off workers - because of the way
  # Unix forking works, we need to make sure we aren't using any of the parent's
  # sockets, e.g. db connection

  defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection
  # Redis and Memcached would go here but their connections are established
  # on demand, so the master never opens a socket
end

unicorn_application_name

#! /bin/sh

### BEGIN INIT INFO
# Provides:          unicorn
# Required-Start:    $all
# Required-Stop:     $network $local_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: starts the unicorn web server
# Description:       starts unicorn
### END INIT INFO

# Change these to match your app:
USER=<USER_WITH_RBENV>
APP_NAME=<APPLICATION_NAME>
APP_PATH=<APPLICATION_PATH>
ENV=<ENVIRONMENT>
RBENV_RUBY_VERSION=<RBENV_RUBY_VERSION>

# env
APP_ROOT="$APP_PATH/$APP_NAME"
RBENV_ROOT="/home/$USER/.rbenv"
PATH="$RBENV_ROOT/bin:$RBENV_ROOT/shims:$PATH"
SET_PATH="cd $APP_ROOT; rbenv rehash; rbenv local $RBENV_RUBY_VERSION"
DAEMON="bundle exec unicorn_rails"
DAEMON_OPTS="-c $APP_ROOT/config/unicorn.rb -E $ENV -D"
CMD="$SET_PATH; $DAEMON $DAEMON_OPTS"
NAME=unicorn
DESC="Unicorn app for $APP_NAME"
PID="$APP_ROOT/tmp/pids/unicorn.pid"
OLD_PID="$PID.oldbin"

cd $APP_ROOT || exit 1

sig () {
        test -s "$PID" && kill -$1 `cat $PID`
}

oldsig () {
        test -s $OLD_PID && kill -$1 `cat $OLD_PID`
}

case ${1-help} in
start)
        sig 0 && echo >&2 "Already running" && exit 0
        su - $USER -c "$CMD"
        ;;
stop)
        sig QUIT && exit 0
        echo >&2 "Not running"
        ;;
force-stop)
        sig TERM && exit 0
        echo >&2 "Not running"
        ;;
restart|reload)
        sig HUP && echo reloaded OK && exit 0
        echo >&2 "Couldn't reload, starting '$CMD' instead"
        su - $USER -c "$CMD"
        ;;
upgrade)
        sig USR2 && exit 0
        echo >&2 "Couldn't upgrade, starting '$CMD' instead"
        su - $USER -c "$CMD"
        ;;
rotate)
        sig USR1 && echo rotated logs OK && exit 0
        echo >&2 "Couldn't rotate logs" && exit 1
        ;;
*)
        echo >&2 "Usage: $0 <start|stop|restart|upgrade|rotate|force-stop>"
        exit 1
        ;;
esac

exit 0