bin/check-cloudwatch-composite-metric.rb
#! /usr/bin/env ruby
#
# check-cloudwatch-composite-metric
#
# DESCRIPTION:
# This plugin retrieves a couple of values of two cloudwatch metrics,
# computes a percentage value based on the numerator metric and the denomicator metric
# and triggers alarms based on the thresholds specified.
# This plugin is an extension to the Andrew Matheny's check-cloudwatch-metric plugin
# and uses the CloudwatchCommon lib, extended as well.
#
# OUTPUT:
# plain-text
#
# PLATFORMS:
# Linux
#
# DEPENDENCIES:
# gem: aws-sdk
# gem: sensu-plugin
#
# USAGE:
# ./check-cloudwatch-composite-metric.rb --namespace AWS/ELB -N HTTPCode_Backend_4XX -D RequestCount --dimensions LoadBalancerName=test-elb --period 60 --statistics Maximum --operator equal --critical 0
#
# NOTES:
#
# LICENSE:
# Cornel Foltea
# Released under the same terms as Sensu (the MIT license); see LICENSE
# for details.
#
require 'sensu-plugins-aws'
require 'sensu-plugin/check/cli'
require 'aws-sdk'
class CloudWatchCompositeMetricCheck < Sensu::Plugin::Check::CLI
option :aws_region,
short: '-r AWS_REGION',
long: '--aws-region REGION',
description: 'AWS Region (defaults to us-east-1).',
default: 'us-east-1'
option :namespace,
description: 'CloudWatch namespace for metric',
short: '-n NAME',
long: '--namespace NAME',
default: 'AWS/EC2'
option :numerator_metric_name,
description: 'Numerator metric name',
short: '-N NAME',
long: '--numerator-metric NAME',
required: true
option :denominator_metric_name,
description: 'Denominator metric name',
short: '-D NAME',
long: '--denominator-metric NAME',
required: true
option :dimensions,
description: 'Comma delimited list of DimName=Value',
short: '-d DIMENSIONS',
long: '--dimensions DIMENSIONS',
proc: proc { |d| CloudwatchCommon.parse_dimensions d },
default: []
option :period,
description: 'CloudWatch metric statistics period. Must be a multiple of 60',
short: '-p N',
long: '--period SECONDS',
default: 60,
proc: proc(&:to_i)
option :statistics,
short: '-s N',
long: '--statistics NAME',
default: 'Average',
description: 'CloudWatch statistics method'
option :unit,
short: '-u UNIT',
long: '--unit UNIT',
description: 'CloudWatch metric unit'
option :critical,
description: 'Trigger a critical when value is over VALUE as a Percent',
short: '-c VALUE',
long: '--critical VALUE',
proc: proc(&:to_f),
required: true
option :warning,
description: 'Trigger a warning when value is over VALUE as a Percent',
short: '-w VALUE',
long: '--warning VALUE',
proc: proc(&:to_f)
option :compare,
description: 'Comparision operator for threshold: equal, not, greater, less',
short: '-o OPERATION',
long: '--operator OPERATION',
default: 'greater'
option :numerator_default,
long: '--numerator-default DEFAULT',
description: 'Default for numerator if no data is returned for metric',
proc: proc(&:to_f)
option :no_denominator_data_ok,
long: '--allow-no-denominator-data',
description: 'Returns ok if no data is returned from denominator metric',
boolean: true,
default: false
option :zero_denominator_data_ok,
long: '--allow-zero-denominator-data',
description: 'Returns ok if denominator metric is zero',
boolean: true,
default: false
option :no_data_ok,
short: '-O',
long: '--allow-no-data',
description: 'Returns ok if no data is returned from either metric',
boolean: true,
default: false
include CloudwatchCommon
def metric_desc
"#{config[:namespace]}-#{config[:numerator_metric_name]}/#{config[:denominator_metric_name]}(#{dimension_string})"
end
def numerator_data(metric_payload)
if resp_has_no_data(metric_payload, config[:statistics])
# If the numerator response has no data in it, see if there was a predefined default.
# If there is no predefined default it will return nil
config[:numerator_default]
else
read_value(metric_payload, config[:statistics]).to_f
end
end
# rubocop:disable Style/GuardClause
def composite_check
numerator_metric_resp = get_metric(config[:numerator_metric_name])
denominator_metric_resp = get_metric(config[:denominator_metric_name])
## If the numerator is empty, then we see if there is a default. If there is a default
## then we will pretend the numerator _isnt_ empty. That is
## if empty but there is no default this will be true. If it is empty and there is a default
## this will be false (i.e. there is data, following standard of dealing in the negative here)
no_num_data = numerator_data(numerator_metric_resp).nil?
no_den_data = resp_has_no_data(denominator_metric_resp, config[:statistics])
no_data = no_num_data || no_den_data
# no data in numerator or denominator this is to keep backwards compatibility
if no_data && config[:no_data_ok]
return :ok, "#{metric_desc} returned no data but that's ok"
elsif no_den_data && config[:no_denominator_data_ok]
return :ok, "#{config[:denominator_metric_name]} returned no data but that's ok"
elsif no_data ## This is legacy case
return :unknown, "#{metric_desc} could not be retrieved"
end
## Now both the denominator and numerator have data (or a valid default)
denominator_value = read_value(denominator_metric_resp, config[:statistics]).to_f
if denominator_value.zero? && config[:zero_denominator_data_ok]
return :ok, "#{metric_desc}: denominator value is zero but that's ok"
elsif denominator_value.zero?
return :unknown, "#{metric_desc}: denominator value is zero"
end
## We already checked if this value is nil so we know its not
numerator_value = numerator_data(numerator_metric_resp)
value = (numerator_value / denominator_value * 100).to_i
base_msg = "#{metric_desc} is #{value}: comparison=#{config[:compare]}"
if compare(value, config[:critical], config[:compare])
return :critical, "#{base_msg} threshold=#{config[:critical]}"
elsif config[:warning] && compare(value, config[:warning], config[:compare])
return :warning, "#{base_msg} threshold=#{config[:warning]}"
else
threshold = config[:warning] || config[:critical]
return :ok, "#{base_msg}, will alarm at #{threshold}"
end
end
# rubocop:enable Style/GuardClause
def run
status, msg = composite_check
if respond_to?(status)
send(status, msg)
else
unknown 'unknown exit status called'
end
end
end