extension simulating yelp/filter_repeated

rb

module Sensu
  module Extension
    class Yelp < Filter
      def name
        "yelp"
      end

      def description
        "filter events using event occurrences"
      end

      def power_of_two?(x)
        while ( x % 2) == 0 and x > 1
          x /= 2
        end
        x==1
      end

      def event_filtered?(event)
        @event = event
        if @event[:check][:name] == 'keepalive'
          interval = 20
        else
          interval      = @event[:check][:interval].to_i || 0
        end
        alert_after   = @event[:check][:alert_after].to_i || 0

        realert_every = ( @event[:check][:realert_every] || 1 ).to_i

        initial_failing_occurrences = interval > 0 ? (alert_after / interval) : 0
        number_of_failed_attempts = @event[:occurrences] - initial_failing_occurrences

        puts "#{@event}"
        puts "interval=#{interval}, alert_after=#{alert_after}, alert_after=#{alert_after}, initial_failing_occurrences=#{initial_failing_occurrences}, number_of_failed_attempts=#{number_of_failed_attempts}"
        if (@event.key?(:occurrences_watermark) &&
          @event[:occurrences_watermark] > initial_failing_occurrences &&
          @event[:action] == :resolve)
          return ["enough occurrences", 1]
        end

        if number_of_failed_attempts < 1
          return ["not enough occurrences", 0]
        elsif interval > 0 and @event[:action] == :create
          if realert_every == -1
            if power_of_two?(number_of_failed_attempts)
              return ["enough occurrences", 1]
            else
              return ["not enough occurrences", 0]
            end
          elsif (number_of_failed_attempts - 1) % realert_every != 0
            return ["not enough occurrences", 0]
          end
        end
        return ["not enough occurrences", 0]
      end

      def run(event)
        yield event_filtered?(event)
      end
    end
  end
end

test:

{
  "checks": {
    "pls_ignore": {
      "command": "ls /tmp/foo",
      "dependencies": [
      ],
      "handlers": [
        "hipchat"
      ],
      "occurrences": 4,
      "refresh": 300,
      "interval": 10,
      "runbook": "https://example.com/",
      "team": "india_ops",
      "alert_after": 40,
      "realert_every": "-1",
      "page": true,
      "ticket": false,
      "region": "vagrant-vagrant",
      "standalone": true,
      "timeout": 10
    }
  }
}

expectation:
handler should trigger when
action == create and

• number_of_failed_attempts > 1
• number_of_failed_attempts is a power of two

handler should trigger when

• action == resolve.

yelp/filter_repeated should not be called at all.

observation:
works as expected.