#!/usr/bin/env ruby

=begin

Munin Plugin for MSSQL - Buffer cache hit ratio monitoring

Author: Wilfred Chau <openapp.developer@gmail.com>
Date: 2011-05-19
Version: 1.0

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License version 2
as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

Prerequistes:
  1) /etc/odbc.ini and /etc/freetds.conf
  2) rubygems
  3) ruby-dbi

Usage:
  1) copy this script to the munin install plugins directory (e.g. /usr/share/munin/plugins)
  2) chmod to allow executable to others
  3) create symbolic link in /etc/munin/plugins
           ln -s /usr/share/munin/plugins/mssql_buffercachehitratio.rb /etc/munin/plugins/mssql_buffercachehitratio.rb

Parameters:
  autoconf
  config (required)

Config variables:
  sqluser : mssql user who has view server state privilege
  sqlpass : password for the mssql user
  dsn     : datasource name as defined in /etc/odbc.ini

#%# family=auto
#%# capabilities=autoconf

=end

require 'rubygems'
require 'dbi'

sqluser  = 'rubyuser'
sqlpass  = 'rubyuser'
dsn      = 'TESTSQL'

#
# Queries
#
#
dbh = DBI.connect("DBI:ODBC:#{dsn}", sqluser, sqlpass)

buffercachehitratio_query = "select (a.cntr_value * 1.0 / b.cntr_value) * 100.0
                            from sys.dm_os_performance_counters a
                            join (select cntr_value, object_name
                                  from sys.dm_os_performance_counters
                                  where counter_name = 'Buffer cache hit ratio base'
                                  and object_name = 'SQLServer:Buffer Manager') b
                            on a.object_name = b.object_name
                            where a.counter_name = 'Buffer cache hit ratio'
                            and a.object_name = 'SQLServer:Buffer Manager'"

#
# autoconf
#
case ARGV[0]
when 'autoconf'
  if all_instance_names.length > 1 && sqluser.length > 1 && sqlpass.length > 1
    puts 'yes'
  else
    puts 'no'
    puts "Usage: #{__FILE__} autoconf|conf"
  end
  exit 0
#
# config definition
#
when 'config'
  puts 'graph_args --base 1000 -r --lower-limit 0'
  puts 'graph_title MSSQL Buffer Cache Hit Ratio '
  puts 'graph_category db'
  puts 'graph_info This graph shows Buffer Cache Hit Ratio'
  puts 'graph_vlabel %'
  puts 'graph_scale no'
  puts 'graph_period second'

  puts 'bc_hitratio.label BufferCacheHitRatio'
  puts 'bc_hitratio.info BufferCacheHitRatio'
  puts 'bc_hitratio.type GAUGE'
  puts 'bc_hitratio.draw LINE1'

  exit 0
end

sth = dbh.execute(buffercachehitratio_query)
sth.fetch do |row|
  puts "bc_hitratio.value #{row[0].strip}"
end
sth.finish
dbh.disconnect