Class: OurEelHacks::Autoscaler

Inherits:
Object
  • Object
show all
Defined in:
lib/our-eel-hacks/autoscaler.rb

Defined Under Namespace

Classes: Limit, LowerLimit, UpperLimit

Constant Summary collapse

MILLIS_PER_DAY = 
24 * 60 * 60 * 1000
API_CALLS_PER_SCALE = 
2

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Autoscaler

Returns a new instance of Autoscaler.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 67

def initialize()
  @dynos = nil
  @soft_side = nil

  @memoed_dyno_info = nil

  @last_scaled = Time.at(0)
  @entered_soft = Time.at(0)
  @last_reading = nil

  @app_name = nil
  @ps_type = nil
  @heroku_api_key = nil

  @min_dynos = 1
  @max_dynos = 10
  @lower_limits = LowerLimit.new(5, 1)
  @upper_limits = UpperLimit.new(30, 50)

  @soft_duration = 10000
  @scaling_frequency = 5000
  @heroku_rate_limit = 80_000
  @heroku_rate_limit_margin = 0.1

  @millis_til_next_scale = nil

  @logger = NullLogger.new
end

Instance Attribute Details

#app_name ⇒ Object

Returns the value of attribute app_name.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def app_name
  @app_name
end

#dynos ⇒ Object (readonly)

Returns the value of attribute dynos.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 124

def dynos
  @dynos
end

#entered_soft ⇒ Object (readonly)

Returns the value of attribute entered_soft.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 124

def entered_soft
  @entered_soft
end

#heroku_api_key ⇒ Object

Returns the value of attribute heroku_api_key.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def heroku_api_key
  @heroku_api_key
end

#heroku_rate_limit ⇒ Object

Returns the value of attribute heroku_rate_limit.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def heroku_rate_limit
  @heroku_rate_limit
end

#heroku_rate_limit_margin ⇒ Object

Returns the value of attribute heroku_rate_limit_margin.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def heroku_rate_limit_margin
  @heroku_rate_limit_margin
end

#last_reading ⇒ Object (readonly)

Returns the value of attribute last_reading.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 124

def last_reading
  @last_reading
end

#last_scaled ⇒ Object (readonly)

Returns the value of attribute last_scaled.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 124

def last_scaled
  @last_scaled
end

#logger ⇒ Object

Returns the value of attribute logger.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def logger
  @logger
end

#lower_limits ⇒ Object

Returns the value of attribute lower_limits.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def lower_limits
  @lower_limits
end

#max_dynos ⇒ Object

Returns the value of attribute max_dynos.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def max_dynos
  @max_dynos
end

#millis_til_next_scale ⇒ Object (readonly)

Returns the value of attribute millis_til_next_scale.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 124

def millis_til_next_scale
  @millis_til_next_scale
end

#min_dynos ⇒ Object

Returns the value of attribute min_dynos.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def min_dynos
  @min_dynos
end

#ps_type ⇒ Object

Returns the value of attribute ps_type.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def ps_type
  @ps_type
end

#scaling_frequency ⇒ Object

Returns the value of attribute scaling_frequency.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def scaling_frequency
  @scaling_frequency
end

#soft_duration ⇒ Object

Returns the value of attribute soft_duration.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def soft_duration
  @soft_duration
end

#soft_side ⇒ Object (readonly)

Returns the value of attribute soft_side.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 124

def soft_side
  @soft_side
end

#upper_limits ⇒ Object

Returns the value of attribute upper_limits.



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# File 'lib/our-eel-hacks/autoscaler.rb', line 122

def upper_limits
  @upper_limits
end

Class Method Details

.configure(flavor = :web, &block) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 19

def configure(flavor = :web, &block)
  get_instance(flavor).configure(flavor, &block)
end

.get_instance(flavor) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 13

def get_instance(flavor)
  flavor = flavor.to_sym
  @instances ||= Hash.new{ |h,k| h[k] = self.new }
  return @instances[flavor]
end

.instance_for(flavor = :web) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 23

def instance_for(flavor = :web)
  instance = get_instance(flavor)
  instance.check_settings
  return instance
end

Instance Method Details

#check_settings ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 106

def check_settings
  errors = []
  errors << "No heroku api key set" if @heroku_api_key.nil?
  errors << "No app name set" if @app_name.nil?
  errors << "No process type set" if @ps_type.nil?
  if (MILLIS_PER_DAY / @heroku_rate_limit) *
    (1.0 - @heroku_rate_limit_margin) *
    API_CALLS_PER_SCALE > @scaling_frequency
    errors << "Scaling frequency will lock up Heroku"
  end
  unless errors.empty?
    logger.warn{ "Problems configuring Autoscaler: #{errors.inspect}" }
    raise "OurEelHacks::Autoscaler, configuration problem: " + errors.join(", ")
  end
end

#clear_dyno_info ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 213

def clear_dyno_info
  @memoed_dyno_info = nil
end

#configure(flavor = nil) {|_self| ... } ⇒ Object

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/our-eel-hacks/autoscaler.rb', line 96

def configure(flavor = nil)
  yield self
  check_settings
  logger.info{ "Autoscaler configured for #{flavor || "{{unknown flavor}}"}"}

  update_dynos(dyno_info.count, Time.now)
  update_scaling_delay(0)
end

#dyno_info ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 217

def dyno_info
  return @memoed_dyno_info ||=
    begin
      regexp = /^#{ps_type}[.].*/
      heroku.ps(app_name).find_all do |dyno|
        dyno["process"] =~ regexp
      end
    end
end

#dynos_stable? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/our-eel-hacks/autoscaler.rb', line 227

def dynos_stable?
  return dyno_info.all? do |dyno|
    dyno["state"] == "up"
  end
end

#elapsed(start, finish) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 126

def elapsed(start, finish)
  seconds = finish.to_i - start.to_i
  micros = finish.usec - start.usec
  diff = seconds * 1000 + micros / 1000
  logger.debug{ "Elapsed: #{start.to_s}:#{finish.to_s} : #{diff}ms" }
  return diff
end

#heroku ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 233

def heroku
  @heroku ||= Heroku::Client.new("", heroku_api_key).tap do |client|
    unless client.info(app_name)[:stack] == "cedar"
      raise "#{self.class.name} built against cedar stack"
    end
  end
end

#scale(metric) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 135

def scale(metric)
  logger.debug{ "Scaling request for #{@ps_type}: metric is: #{metric}" }
  moment = Time.now
  if elapsed(last_scaled, moment) < millis_til_next_scale
    logger.debug{ "Not scaling: elapsed #{elapsed(last_scaled, moment)} less than computed #{millis_til_next_scale}" }
    return
  end

  clear_dyno_info

  starting_wait = millis_til_next_scale

  update_dynos(dyno_info.count, moment)

  target_dynos = target_scale(metric, moment)

  target_dynos = [[target_dynos, max_dynos].min, min_dynos].max
  logger.debug{ "Target dynos at: #{min_dynos}/#{target_dynos}/#{max_dynos} (vs. current: #{@dynos})" }

  set_dynos(target_dynos, moment)

  update_scaling_delay(starting_wait)
rescue => ex
  logger.warn{ "Problem scaling: #{ex.inspect} \t#{ex.backtrace.join("\t\n")}" }
end

#set_dynos(count, moment) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 241

def set_dynos(count,moment)
  if count == dynos
    logger.debug{ "Not scaling: #{count} ?= #{dynos}" }
    return
  end

  if not (stable = dynos_stable?)
    logger.debug{ "Not scaling: dynos not stable (iow: not all #{ps_type} dynos are up)" }
    return
  end
  logger.info{ "Scaling from #{dynos} to #{count} dynos for #{ps_type}" }
  heroku.ps_scale(app_name, :type => ps_type, :qty => count)
  update_dynos(count, moment)
end

#soft_limit(metric, moment) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 172

def soft_limit(metric, moment)
  hit_limit = [lower_limits, upper_limits].find{|lim| lim.includes? metric}

  if soft_side == hit_limit
    if elapsed(entered_soft, moment) > soft_duration
      entered_soft = moment
      case hit_limit
      when upper_limits
        return +1
      when lower_limits
        return -1
      else
        return 0
      end
    else
      return 0
    end
  else
    @entered_soft = moment
  end

  @soft_side = hit_limit
  return 0
end

#target_scale(metric, moment) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 161

def target_scale(metric, moment)
  if lower_limits > metric
    return dynos - 1
  elsif upper_limits < metric
    return dynos + 1
  elsif
    result = (dynos + soft_limit(metric, moment))
    return result
  end
end

#update_dynos(new_value, moment) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 204

def update_dynos(new_value, moment)
  if new_value != dynos
    @last_scaled = moment
    @entered_soft = moment
  end
  @dynos = new_value
  @last_reading = moment
end

#update_scaling_delay(starting_wait) ⇒ Object 



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# File 'lib/our-eel-hacks/autoscaler.rb', line 197

def update_scaling_delay(starting_wait)
  @millis_til_next_scale = scaling_frequency * @dynos
  if starting_wait > millis_til_next_scale
    @millis_til_next_scale = rand((@millis_til_next_scale..starting_wait))
  end
end