Ruby Memory Leak Examples

1.callback.rb

module Logger
  extend self

  attr_accessor :output, :log_actions


  def log(&event)
    self.log_actions ||= []
    self.log_actions << event
  end


  def play
    output = []
    log_actions.each { |e| e.call(output) }
    puts output.join("\n")
  end
end


class Thing
  def initialize(id)
    # Leaded self here
    Logger.log { |output| output << "created thing" }
  end
end


def do_something
  1000.times { |i| Thing.new(i) }
end


do_something

GC.start

Logger.play

puts ObjectSpace.each_object(Thing).count

1.callback_safe.rb

module Logger
  extend self
  attr_accessor :output
 	
  def log(&event)
    self.output ||= []
    event.call(output)
  end
 	
 	
  def play
    puts output.join("\n")
  end
end
 	
 	
class Thing
  def initialize(id)
    Logger.log { |output| output << "created thing #{id}" }
  end
end
 	
 	
def do_something
  1000.times { |i| Thing.new(i) }
end
 	
 	
do_something
 	
GC.start
 	
Logger.play
 	
puts ObjectSpace.each_object(Thing).count

1.no_callback.rb

module Logger
  extend self

  attr_accessor :output, :log_actions


  def log(line)
    self.log_actions ||= []
    self.log_actions << line
  end


  def play
    log_actions.each { |line| puts line }
  end
end


class Thing
  def initialize(id)
    Logger.log "created thing #{id}"
  end
end


def do_something
  1000.times { |i| Thing.new(i) }
end

do_something
Logger.play
Logger.log_actions = []

GC.start
puts ObjectSpace.each_object(Thing).count

2.singal.rb

class LargeObject
  def initialize
    @data = "x" * 1024 * 1024 * 20
  end
end

def do_something
  obj = LargeObject.new
  trap("TERM") { puts 'oops' } 
end

do_something

# force major GC to make sure we free all objects that can be freed
GC.start(full_mark: true, immediate_sweep: true)
puts "LargeObject instances left in memory: %d" %
  ObjectSpace.each_object(LargeObject).count