Copyright (C) 2006 Peter J Jones (pjones@pmade.com).

################################################################################
# This script will update your monit configuration file to monitor your
# mongrel cluster by reading the mongrel cluster file and generating monit
# check entries.  It places delimiters in the configuration file so that you
# can run this script multiple times without generating duplicate entries.
#
# Run it like this:
#
#  mongrel_monit --mongrel=/path/to/mongrel/config.yml --monit=/path/to/monitrc
#
# You can edit the ERB template below to control the generated monit config.
#


TEMPLATE = <<EOT
check process mongrel_<%= @port %> with pidfile <%= @pidfile %>
  group mongrel
  start program = "/usr/local/bin/<%= @start %>"
  stop program = "/usr/local/bin/<%= @stop %>"

  if failed host 127.0.0.1 port <%= @port %> protocol http
    with timeout 10 seconds
    then restart

  if totalmem > 100 Mb then restart
  if cpu is greater than 60% for 2 cycles then alert
  #if cpu > 90% for 5 cycles then restart
  #if loadavg(5min) greater than 10 for 8 cycles then restart
  if 3 restarts within 5 cycles then timeout

EOT
################################################################################
require 'erb'
require 'optparse'
require 'fileutils'
require 'rubygems'
require 'mongrel_cluster/init'
################################################################################
module Kernel
  $commands = []

  # Hack Kernel::` so that we can capture what mongrel_cluster does
  def ` (cmd)
    $commands << cmd
    system(':') # to set $?
  end

  # Hack Kernel::puts to shut mongrel_cluster up
  def puts (str)
    true
  end
end
################################################################################
options = OptionParser.new

options.on('--mongrel=FILE', 'Mongrel configuration file') do |o|
  $mongrel_config = o
end

options.on('--monit=FILE', 'Monit configuration file') do |o|
  $monit_config = o
end

options.parse!

unless $mongrel_config and $monit_config
  puts "please give --mongrel and --monit"
  exit 1
end
################################################################################
mongrel_config_data = YAML.load_file($mongrel_config)
Dir.chdir(mongrel_config_data['cwd']) if mongrel_config_data['cwd']
################################################################################
# This is the only way to access the cmd that mongrel_cluster uses so that we
# can keep things DRY
start = Cluster::Start.new
start.instance_variable_set(:@config_file, $mongrel_config)
start.run
start_commands = $commands.dup
$commands.clear

stop = Cluster::Stop.new
stop.instance_variable_set(:@config_file, $mongrel_config)
stop.run
stop_commands = $commands.dup
$commands.clear
################################################################################
template = ERB.new(TEMPLATE)
config = ''

0.upto(start_commands.length - 1) do |i|
  @port = start_commands[i].match(/-p\s*(\d+)/)[1]
  @pidfile = File.expand_path(start_commands[i].match(/-P\s*(\S+)/)[1])
  @start = start_commands[i]
  @stop = stop_commands[i]
  config << template.result(binding)
end
################################################################################
monit_config_data = File.open($monit_config) {|f| f.read}

# TODO: if you have more than one cluster, this won't do
banner_start = "#= Mongrel_Monit Config Start =#\n"
banner_stop  = "#= Mongrel_Monit Config End =#\n"

if monit_config_data.match(/#{banner_start}.*#{banner_stop}/m)
  monit_config_data.sub!(/#{banner_start}.*#{banner_stop}/m, "#{banner_start}#{config}#{banner_stop}")
else
  monit_config_data << "#{banner_start}#{config}#{banner_stop}"
end

File.open($monit_config, 'w') {|f| f << monit_config_data}
################################################################################

Put it in yr httpd.conf, or better yet, an included file. (that thing is monstrous as is)

<VirtualHost *:80>
        ServerName test.com
        DirectoryIndex index.html dispatch.fcgi
        DocumentRoot /domains/test.com/web/public
        RewriteEngine On
        RewriteRule ^(.*/)?.svn/ - [F,L]
        ProxyPass /images !
        ProxyPass /stylesheets !
        ProxyPass /javascripts !
        ProxyPass /examples !
        ProxyPass /map_data !
        ProxyPass /engine_files !
        ProxyPass /javascript !
        ProxyPass /feregions !
        ProxyPass / balancer://test/
        ProxyPassReverse / balancer://test
        ProxyPreserveHost On
        ErrorLog /opt/csw/apache2/var/log/test.com.error
        CustomLog /opt/csw/apache2/var/log/test.com common

        <Proxy balancer://test>
                BalancerMember http://127.0.0.1:8000
                BalancerMember http://127.0.0.1:8001
                BalancerMember http://127.0.0.1:8002
                BalancerMember http://127.0.0.1:8003
                BalancerMember http://127.0.0.1:8004
        Proxy>
</VirtualHost>