Unicorn / Monit setup

attributes.rb

default['unicorn']['before_fork']       = %Q(
  defined?(ActiveRecord::Base) && ActiveRecord::Base.connection.disconnect!

  old_pid = '#{node['unicorn']['pid']}.oldbin'
  if File.exists?(old_pid) && server.pid != old_pid
    begin
      Process.kill('QUIT', File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
      puts 'Old master alerady dead'
    end
  end
)
default['unicorn']['after_fork']        = %q(
  defined?(ActiveRecord::Base) && ActiveRecord::Base.establish_connection
  child_pid = server.config[:pid].sub('.pid', ".#{worker.nr}.pid")
  system("echo #{Process.pid} > #{child_pid}")
)

unicorn-config.rb

##
# Unicorn config for <%= @identifier %>
# Managed by Chef - Local Changes will be obliterated
##

user "<%= @user %>"<%= @group ? %Q(, "#{@group}") : '' %>
timeout <%= @worker_timeout %>
preload_app <%= @preload_app %>
worker_processes <%= @worker_processes %>
pid '<%= @pid %>'
<% @listen.each do |listen| %>
listen "<%= listen[0] %>"<%= listen[1] ? %Q(, "#{listen[1]}") : '' %>
<% end %>
<% if @working_directory %>
working_directory '<%= @working_directory %>'
<% end %>
<% if @before_exec %>
before_exec do |server|
  <%= @before_exec %>
end
<% end %>
<% if @before_fork %>
before_fork do |server, worker|
  <%= @before_fork %>
end
<% end %>
<% if @after_fork %>
after_fork do |server, worker|
  <%= @after_fork %>
end
<% end %>
<% if @stderr_path %>
stderr_path '<%= @stderr_path %>'
<% end %>
<% if @stdout_path %>
stdout_path '<%= @stdout_path %>'
<%- end %>

unicorn-init.sh

#!/bin/bash
# /etc/init.d/unicorn
# To install: update-rc.d unicorn defaults

### BEGIN INIT INFO
# Provides:   unicorn
# Required-Start:    $local_fs $remote_fs
# Required-Stop:     $local_fs $remote_fs
# Should-Start:      $network
# Should-Stop:       $network
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Unicorn server
# Description:       Starts the unicorn server
### END INIT INFO

set -u
set -e

TIMEOUT=<%= @timeout %>
CMD="unicorn-<%= @environment %>"
PID="<%= @pid %>"
OLDPID="$PID.oldbin"

cd <%= @root %> || exit 1

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

workersig () {
  workerpid=${PID/.pid/$2.pid}
  test -s "$workerpid" && kill -$1 `cat $workerpid`
}

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

start() {
  su -l -c '<%= @command %>' <%= @user %>
}

case $1 in
start)
  sig 0 && echo >&2 "Already running" && exit 0
  start
  ;;
stop)
  sig QUIT && exit 0
  echo >&2 "Not running"
  test -s $PID && rm $PID
  ;;
force-stop)
  sig TERM && exit 0
  echo >&2 "Not running"
  test -s $PID && rm $PID
  ;;
reload)
  sig HUP && echo reloaded OK && exit 0
  echo >&2 "Couldn't reload, starting unicorn-<%= @environment %> instead"
  start
  ;;
status)
  test -s $PID && test -d "/proc/`cat $PID`" && echo running && exit 0
  echo stopped && exit 3
  ;;
restart)
  sig USR2 && sleep 2 && sig 0 && exit 0
  echo >&2 "Couldn't restart, starting unicorn-<%= @environment %> instead"
  start
  ;;
kill_worker)
  workersig QUIT $2 && exit 0
  echo >&2 "Worker not running"
  ;;
rotate)
  sig USR1 && echo rotated logs OK && exit 0
  echo >&2 "Couldn't rotate logs" && exit 1
  ;;
*)
  echo >&2 "Usage: $0 <start|stop|restart|rotate|force-stop|kill_worker>"
  exit 1
  ;;
esac

unicorn_worker_0.monitrc

check process unicorn_worker_0
with pidfile /path/to/your/app/shared/pids/unicorn.0.pid
start program = "/bin/cat /dev/null"
stop program = "/etc/init.d/unicorn kill_worker 0"
if mem is greater than 175.0 MB for 1 cycles then restart
if cpu is greater than 22% for 2 cycles then alert         
if cpu is greater than 25% for 1 cycles then restart