mysql_slave_checker.rb

#!/usr/bin/env ruby
require 'rubygems'
require 'mysql'

module Kauperts
	class MysqlSlaveChecker

		class SlaveNotRunningError < Exception; end

		attr_reader :connection
		attr_reader :slave_status

		#
		def initialize(attributes = {})
			attributes.each do |attr,value|
				instance_variable_set :"@#{attr}", value
			end
			get_slave_status
		end

		# Checks if the slave io and the slave sql processes are running
		# as well as the seconds behind master.
		#
		# === Parameters
		# * +seconds_behind_master_threshold+: consider a delay for this many seconds to not be ok (default: 1800)
		def ok?(seconds_behind_master_threshold = 1800)
			self.slave_io_running && self.slave_sql_running && self.seconds_behind_master < seconds_behind_master_threshold
		end

		private

		def establish_connection!
			# Mysql.new(host=nil, user=nil, passwd=nil, db=nil, port=nil, sock=nil, flag=nil)
			@connection ||= Mysql.new(@host, @username, @password, nil, @port, @socket, @flag)
		end

		def get_slave_status
			establish_connection!
			rs = @connection.query('SHOW SLAVE STATUS')

			# nb: it's only one hash
			rs.each_hash { |h| @slave_status = h }
			raise SlaveNotRunningError.new unless @slave_status

			@slave_status.each do |k, value|
				meth = Proc.new{converted_value(value)}
				self.class.send(:define_method, k.downcase, meth)
			end

			# Does simple type sanitizing for SHOW SLAVE STATUS output
			def converted_value(value)
				if value.downcase == 'yes' or value.downcase == 'no'
					value.downcase == 'yes'
				elsif value ==  '' or value.nil?
					nil
				elsif /^\d+$/.match(value)
					value.to_i
				else
					value
				end
			end

		end

	end
end

options = {
	:host => ENV['MYSQL_HOST'],
	:socket => ENV['MYSQL_SOCKET'],
	:username => (ENV['MYSQL_USERNAME'] || 'root'),
	:password => ENV['MYSQL_PASSWORD']
}

begin
	checker = Kauperts::MysqlSlaveChecker.new(options)

	# Do whatever you want to do with the status info you got now.
	# Example:
	# puts "Seconds behind Master : #{checker.seconds_behind_master}"
	# puts "Slave IO running..... : #{checker.slave_io_running}"
	# puts "Slave SQL running.... : #{checker.slave_sql_running}"

	checker.ok? ? exit(0) : exit(1)

rescue Kauperts::MysqlSlaveChecker::SlaveNotRunningError => e
	puts "E: Slave not running"
	exit 1
end