Class: Vector::Function::PredictiveScaling

Inherits:
Object
  • Object
show all
Includes:
HLogger
Defined in:
lib/vector/functions/predictive_scaling.rb

Instance Method Summary collapse

Methods included from HLogger

enable, #hlog, #hlog_ctx

Constructor Details

#initialize(options) ⇒ PredictiveScaling

Returns a new instance of PredictiveScaling.



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# File 'lib/vector/functions/predictive_scaling.rb', line 6

def initialize(options)
  @cloudwatch = options[:cloudwatch]
  @lookback_windows = options[:lookback_windows]
  @lookahead_window = options[:lookahead_window]
  @valid_threshold = options[:valid_threshold]
  @valid_period = options[:valid_period]
end

Instance Method Details

#run_for(group) ⇒ Object 



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# File 'lib/vector/functions/predictive_scaling.rb', line 14

def run_for(group)
  result = { :check_procs => [], :triggered => false }

  hlog_ctx "group: #{group.name}" do
    return result if @lookback_windows.length == 0

    scaleup_policies = group.scaling_policies.select do |policy|
      policy.scaling_adjustment > 0
    end

    scaleup_policies.each do |policy|
      hlog_ctx "policy: #{policy.name}" do

        policy.alarms.keys.each do |alarm_name|
          alarm = @cloudwatch.alarms[alarm_name]
          hlog_ctx "alarm: #{alarm.name} (metric #{alarm.metric.name})" do

            unless alarm.enabled?
              hlog "Skipping disabled alarm"
              next
            end

            # Note that everywhere we say "load" what we mean is
            # "metric value * number of nodes"
            now_load, now_num = load_for(group, alarm.metric,
              Time.now, @valid_period)

            if now_load.nil?
              hlog "Could not get current total for metric"
              next
            end

            @lookback_windows.each do |window|
              hlog_ctx "window: #{window.inspect}" do
                then_load, = load_for(group, alarm.metric,
                  Time.now - window, @valid_period)

                if then_load.nil?
                  hlog "Could not get past total value for metric"
                  next
                end

                # check that the past total utilization is within
                # threshold% of the current total utilization
                if @valid_threshold &&
                  !Vector.within_threshold(@valid_threshold, now_load, then_load)
                  hlog "Past metric total value not within threshold (current #{now_load}, then #{then_load})"
                  next
                end

                past_load, = load_for(group, alarm.metric,
                  Time.now - window + @lookahead_window,
                  alarm.period)

                if past_load.nil?
                  hlog "Could not get past + #{@lookahead_window.inspect} total value for metric"
                  next
                end

                # now take the past total load and divide it by the
                # current number of instances to get the predicted value
                check_proc = Proc.new do |num_nodes|
                  predicted_value = past_load.to_f / num_nodes
                  hlog "Predicted #{alarm.metric.name}: #{predicted_value} (#{num_nodes} nodes)"

                  check_alarm_threshold(alarm, predicted_value)
                end
                result[:check_procs] << check_proc

                if check_proc.call(now_num)
                  hlog "Executing policy"
                  policy.execute(honor_cooldown: true)

                  result[:triggered] = true

                  # don't need to evaluate further windows or policies on this group
                  return result
                end
              end
            end
          end
        end
      end
    end
  end

  result
end