Class: Alicorn::Scaler

Inherits:
Object
  • Object
show all
Defined in:
lib/alicorn/scaler.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ Scaler

Returns a new instance of Scaler.



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# File 'lib/alicorn/scaler.rb', line 14

def initialize(options = {})
  @min_workers        = options[:min_workers]         || 1
  @max_workers        = options[:max_workers]
  @target_ratio       = options[:target_ratio]        || 1.3
  @buffer             = options[:buffer]              || 2
  @listener_type      = options[:listener_type]       || "tcp"
  @listener_address   = options[:listener_address]    || "0.0.0.0:80"
  @delay              = options[:delay]               || 1
  @sample_count       = options[:sample_count]        || 30
  @app_name           = options[:app_name]            || "unicorn"
  @dry_run            = options[:dry_run]
  @signal_delay       = 0.5
  log_path            = options[:log_path]            || "/dev/null"

  self.logger = Logger.new(log_path)
  logger.level = options[:verbose] ? Logger::DEBUG : Logger::WARN
end

Instance Attribute Details

#app_name ⇒ Object

Returns the value of attribute app_name.



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# File 'lib/alicorn/scaler.rb', line 8

def app_name
  @app_name
end

#buffer ⇒ Object

Returns the value of attribute buffer.



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# File 'lib/alicorn/scaler.rb', line 8

def buffer
  @buffer
end

#delay ⇒ Object

Returns the value of attribute delay.



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# File 'lib/alicorn/scaler.rb', line 8

def delay
  @delay
end

#dry_run ⇒ Object

Returns the value of attribute dry_run.



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# File 'lib/alicorn/scaler.rb', line 8

def dry_run
  @dry_run
end

#listener_address ⇒ Object

Returns the value of attribute listener_address.



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# File 'lib/alicorn/scaler.rb', line 8

def listener_address
  @listener_address
end

#listener_type ⇒ Object

Returns the value of attribute listener_type.



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# File 'lib/alicorn/scaler.rb', line 8

def listener_type
  @listener_type
end

#logger ⇒ Object

Returns the value of attribute logger.



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# File 'lib/alicorn/scaler.rb', line 8

def logger
  @logger
end

#max_workers ⇒ Object

Returns the value of attribute max_workers.



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# File 'lib/alicorn/scaler.rb', line 8

def max_workers
  @max_workers
end

#min_workers ⇒ Object

Returns the value of attribute min_workers.



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# File 'lib/alicorn/scaler.rb', line 8

def min_workers
  @min_workers
end

#sample_count ⇒ Object

Returns the value of attribute sample_count.



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# File 'lib/alicorn/scaler.rb', line 8

def sample_count
  @sample_count
end

#signal_delay ⇒ Object (readonly)

Returns the value of attribute signal_delay.



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# File 'lib/alicorn/scaler.rb', line 12

def signal_delay
  @signal_delay
end

#target_ratio ⇒ Object

Returns the value of attribute target_ratio.



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# File 'lib/alicorn/scaler.rb', line 8

def target_ratio
  @target_ratio
end

Instance Method Details

#auto_scale(data, worker_count) ⇒ Object 



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# File 'lib/alicorn/scaler.rb', line 51

def auto_scale(data, worker_count)
  return nil if data[:active].empty? or data[:queued].empty?
  connections = data[:active].zip(data[:queued]).map { |e| e.inject(:+) }
  connections = DataSet.new(connections)

  # Calculate target
  target = connections.max * target_ratio + buffer

  # Check hard thresholds
  target = max_workers if max_workers and target > max_workers
  target = min_workers if target < min_workers
  target = target.ceil

  logger.debug "target calculated at: #{target}, worker count at #{worker_count}"
  if worker_count == max_workers and target == max_workers
    logger.warn "at maximum capacity! cannot scale up"
    return nil, 0
  elsif connections.avg > worker_count and data[:queued].avg > 1
    logger.warn "danger, will robinson! scaling up fast!"
    return "TTIN", target - worker_count
  elsif target > worker_count
    logger.debug "scaling up!"
    return "TTIN", 1
  elsif target < worker_count
    logger.debug "scaling down!"
    return "TTOU", 1
  elsif target == worker_count
    logger.debug "just right!"
    return nil, 0
  end
end

#scale ⇒ Object 



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# File 'lib/alicorn/scaler.rb', line 32

def scale
  data          = collect_data
  unicorns      = find_unicorns

  master_pid    = find_master_pid(unicorns)
  worker_count  = find_worker_count(unicorns)

  sig, number = auto_scale(data, worker_count)
  if sig and !dry_run
    number.times do
      send_signal(master_pid, sig) 
      sleep(signal_delay) # Make sure unicorn doesn't discard repeated signals
    end
  end
rescue StandardError => e
  logger.error "exception occurred: #{e.class}\n\n#{e.message}"
  raise e unless e.is_a?(AmbiguousMasterError) or e.is_a?(NoMasterError) # Master-related errors are fine, usually just indicate a start or restart
end