#!/usr/bin/env ruby
#
# Nagios plugin to monitor Redis sentinel
#
# Checks general connectivity to a Redis sentinel server and will go critical
# for any of the following conditions:
#   * Inability to connect to the sentinel server
#   * Sentinel reports it isn't monitoring any masters
#   * Sentinel has entered TILT mode
#
# Arguments:
# -H --host HOSTNAME to connect to (defaults to 127.0.0.1)
# -p --port PORT to connect to (defaults to 26379)
#
# Requires the "redis" Rubygem
#
# Author: Chris Boulton <chris@chrisboulton.com>
# License: MIT (http://www.opensource.org/licenses/mit-license.php)
#
 
require 'redis'
require 'optparse'
 
STATES = {
  :ok       => 0,
  :warning  => 1,
  :critical => 2,
  :unknown  => 3,
}
 
options = {
  :host    => '127.0.0.1',
  :port    => 26379,
  :timeout => 2,
}
 
$results     = []
$exit_status = :ok
 
def add_state(status, msg, should_exit = false)
  $results.push(msg)
  $exit_status = status if STATES[status] > STATES[$exit_status]
  if should_exit
    do_exit
  end
end
 
def add_info(msg)
  $results.push(msg)
end
 
def do_exit
  puts "#{$exit_status.upcase} - #{$results.join('. ')}"
  exit STATES[$exit_status]
end
 
optparse = OptionParser.new do |opts|
  opts.on('-H', '--host HOST', 'Hostname') do |h|
    options[:host] = h
  end
 
  opts.on('-p', '--port PORT', 'Port') do |p|
    options[:port] = p.to_i
  end
end
optparse.parse!
 
begin
  redis = Redis.new(:host => options[:host], :port => options[:port], :timeout => options[:timeout])
 
  info = redis.info
  add_state(:critical, "Redis instance is not configured as a sentinel", true)  unless info['sentinel_masters']
  add_state(:critical, "Sentinel has entered TILT mode", true) if info['sentinel_tilt'] != '0'
 
  if info['sentinel_masters'] == '0'
    add_state(:critical, "Sentinel is not monitoring any masters", true) 
  else
    add_info("Monitoring #{info['sentinel_masters']} masters")
  end
rescue Redis::CannotConnectError => e
  add_state(:critical, e, true)
end
 
do_exit