Dogslow like functionality for Rack and Rails

development.rb

#Add this to your development.rb
config.middleware.use DogslowRack

dogslow_rack.rb

#create it in app/middleware

class DogslowRack
  FILE_PATH = File.expand_path(__FILE__)

  def initialize(app, options={})
    @wdt = Thread.new do
      Thread.current.abort_on_exception = true
      loop do
        sleep 2 #sampling is 2sec
        Thread.list.each do |thread|
          if thread[:request_start_time] && thread[:request_start_time] < Time.now - 10.seconds
            thread[:request_start_time] = nil
            puts "Slow thread TID-#{thread.object_id.to_s(36)}"
            app_trace = thread.backtrace.take_while{|frame| !frame.starts_with?(FILE_PATH)}
            puts app_trace.join("\n")
          end
        end
      end
    end
    puts "Started DogslowRack as #{@wdt}"
  end

  def call(env)
    Thread.current[:request_start_time] = Time.now

    @app.call(env)
  ensure
    Thread.current[:request_start_time] = nil
  end

end