Mtrc (Metric, for short)

A small library to accumulate metrics and extract basic statistics from them. Want a latency profile of your Rack app?

gem install mtrc

Middleware!:

class MyMetrics
  def initialize(app)
    @app = app
    @m = Mtrc::SortedSamples.new

    Thread.new do
      sleep 100
      puts <<EOF
Min:      #{@m.min}
Median:   #{@m.median}
95th %:   #{@m % 95}
99th %:   #{@m % 99}
99.9th %: #{@m.at .999}
Max:      #{@m.max}
EOF
      @m = Mtrc::SortedSamples.new
    end
  end

  def call(env)
    t1 = Time.now
    r = @app.call env
    dt = Time.now - t1

    @m << dt
    r
  end        
end

Which requests take the longest?

@m << Mtrc::Sample.new dt, env[:PATH_INFO]
(@m % 95).value # => "?bacon=strips&bacon=strips&bacon=strips"

Rates

r = Mtrc::Rate.new
10.times do
  r.tick 2
end
sleep 1
r.rate #=> 19.999...

License

MIT.