#! /usr/bin/env ruby
#
# metrics-ec2-filter
#
# DESCRIPTION:
#   This plugin retrieves EC2 instances matching a given filter
#
# OUTPUT:
#   plain-text
#
# PLATFORMS:
#   Linux
#
# DEPENDENCIES:
#   gem: aws-sdk
#   gem: sensu-plugin
#
# USAGE:
#   ./metrics-ec2-filter.rb -f "{name:tag-value,values:[infrastructure]}"
#   ./metrics-ec2-filter.rb -f "{name:tag-value,values:[infrastructure]} {name:instance-state-name,values:[running]}"
#
# NOTES:
#
# LICENSE:
#   Justin McCarty
#   Released under the same terms as Sensu (the MIT license); see LICENSE
#   for details.
#

require 'sensu-plugin/metric/cli'
require 'aws-sdk'
require 'sensu-plugins-aws'

class EC2Filter < Sensu::Plugin::Metric::CLI::Graphite
  include Filter
  include Common

  option :aws_region,
         short: '-r AWS_REGION',
         long: '--aws-region REGION',
         description: 'AWS Region (defaults to us-east-1).',
         default: 'us-east-1'

  option :name,
         description: 'Filter naming scheme, text to prepend to metric',
         short: '-n NAME',
         long: '--name NAME',
         default: ''

  option :filter,
         short: '-f FILTER',
         long: '--filter FILTER',
         description: 'String representation of the filter to apply',
         default: '{}'

  option :scheme,
         description: 'Metric naming scheme, text to prepend to metric',
         short: '-s SCHEME',
         long: '--scheme SCHEME',
         default: 'sensu.aws.ec2'

  def aws_config
    { access_key_id: config[:aws_access_key],
      secret_access_key: config[:aws_secret_access_key],
      region: config[:aws_region] }
  end

  def run
    begin
      client = Aws::EC2::Client.new aws_config

      filter = Filter.parse(config[:filter])

      options = { filters: filter }

      data = client.describe_instances(options)

      instance_ids = Set.new
      scheme = config[:scheme]

      unless config[:name].empty?
        scheme += ".#{config[:name]}"
      end
      data[:reservations].each do |res|
        res[:instances].each do |i|
          instance_ids << i[:instance_id]
          output scheme + ".ids.#{i[:instance_id]}"
        end
      end
      output scheme + ".count.#{instance_ids.count}"
    rescue StandardError => e
      puts "Error: exception: #{e}"
      critical
    end
    ok
  end
end